Home

Spinmaster FFC2000 V1073

1. 04 22 2 5 5 Field homogeneity adjustment 0 0 ce eee eens 23 2 0 Troubleshooting os xiv er Rr eed tee tae AG E EM EPOR 24 2 5 1 Safety interlocks eneore ot Fas od etes ote dau edes 24 2 0 2 Maintenance res COME aereo Ia Mns pute a uas 25 2 6 3 Problems and Actions 5 Less cer a eret Aeg e eres P RO eR 26 24 Data Acquisition principles oi coy cota quet Piae LESE DUO EE Ed 31 2 7 1 Preparing for an acquisitlon ced axe e ee SCR TERRE UAR 31 2 7 2 Data normalization 15 001 05 eos rne pee ue e aet rad 32 2 7 3 Hardware aspects of acquisition 00 0 suana 32 2 7 4 Quadrature detection nananana naene 32 Zao Phase cycling vo va td ame Rab ea SU a PR ata a 33 2 7 5 1 Phase cycling in NMR ie be re RE RES 33 2 7 5 2 Basics of phase encoding 0 000 e eee 34 2 7 5 3 Interrupted cycles coo o3 Seve Hr ES ped oes Won 35 2 7 5 4 Quadrature detection QD Phase cycling 36 2 7 5 5 Table of implemented Receiver phases 37 2 7 5 6 Decoupler AND OR X device cycling 37 2 7 5 7 Elimination of instrumental artifacts 38 2 7 5 8 Compensation of Equipment imperfections 39 2 7 5 9 Zero offset elimination in LR NMR 40 2 7 5 10 Suppression of the acoustic ringing 40 2 7 5 11 Phase cycle filters for genuine FFC components 41 Copyright Stelar s r 1 2001 Stelar SPINMSTER FFC2
2. The order in which the device script lines appear may is irrelevant Extra white space blanks tabulators empty lines is ignored Each script line contains one to two fields separated by a vertical bar The first field is the TypeScript the second is the InterfaceScript Within each field there is a number of items separated by commas TypeScript items 1 Device type a decadic number The type denotes particular type make of the device When type 0 the device is absent and the rest of the line is ignored 2 The consecutive items are called Type Configuration parameters They may be either decadic e g 13 or hex 0xD numbers which shall be loaded into a parameter s type configuration array Their interpretation is device and type dependent and is normally explained on a comment line within the Hardware def file which follows the particular device definition script line InterfaceScript items when present 1 Name of the interface device driver void if there is none The driver is a device carrying out the actual interface actions and its definition script must appear among somewhere in the file Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 99 of 99 2 Name of an interfaced parameter void if there is none A device may not have more than one interfaced parameter To interface more than one parameter one must define owned sub devices each associated with one of the paramete
3. times and polarising pulses few ms F button in Fig 3 e The compensation system should be switched off for very short relaxation To set proper temperature compensation it is crucial to know the rate of magnetic field shift due to the thermal jump of the magnet after a current pulse The magnetic field shift can be evaluated by measuring the frequency shift in the NMR signal while the thermal jump can be estimated from the magnet temperature display at the front panel of the Power Supply set the display to AT I in Fig 3 The coefficient describing the proportionality between NMR frequency shift and temperature jump is displayed under hard in Acq parameter page MTCF Magnet temperature compensation factor Hz deg The relationship between frequency shift Av and temperature change AT is approximately linear and the coefficients are originally set at the factory To activate the temperature compensation system switch it on using the green button F in Fig 3 located at the Field Regulation panel of the Magnet Power Supply The AT NULL regulation can be adjusted to a sufficiently low value close to zero when no current is passing through the magnet This situation is convenient while dealing with low or medium T dispersion The user may re calibrate MTCF and AT with the procedure described in Section 3 9 For samples with very high relaxometric dispersion and long T at higher fields it is recommended to set AT NULL
4. lt grid type gt is either LIN linear or LOG logarithmic and lt number of points gt has the plain language meaning An example of a valid elementary range specification is 10 0 01 LOG 15 Notes lt first value gt may be greater equal to or smaller than lt final value gt In the case of LOG distribution a value smaller than 1e 6 s e g 0 is automatically handled as le 6 The separators and are completely interchangeable Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 47 of 47 Unlike in case 1 the number of blocks specified by NBLK need not necessarily coincide with the total number of values in the multi range In such a case when NBLK is smaller only the first NBLK listed values shall be considered otherwise when NBLK be greater the multi range list is stepped through cyclically in general however Users are likely to keep the two values identical The final point a User should bear in mind is the that the parameters BINI and BEND in the first case as well as all numeric values in the second case except number of points may be expressions containing other parameters as arguments Thus for example the following multi range specification is legal 0 TIMX 0 01 LOG 16 4 T1MX 0 05 LIN 15 3 Tutorial 3 1 Signal Location and Conditioning 1 Sample preparation Use a sample with good S N and short T few milliseconds Water doped with MnCl 2mM conc
5. List of main menu items Tools Evaluate Hardware Configuration View Help Exit Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 63 of 63 Tools The Tools entry of the main menu contains these submenus and commands Load parameters to load parameters from a file Save parameters to save current parameters in a parameter file Clear modified flags to remove the modified parameter flags and display enhancements List pulse sequence to print the detailed list of pulser channel settings in current sequence Execute macro to run a macro command Load parameters Full sets of program parameters can be loaded from two different sources parameter files or data files The Load parameters submenu part of the main menu Tools therefore contains two items from a Parameter file To load a complete set of system parameters from a previously saved parameters file use this submenu and select the option from a parameters file When a file open dialog appears select an existing parameters file default extension par and press the Open button to load the set of parameters it contains Not all parameters are loaded Some parameters such as those describing the instrument s hardware configuration may not be modified at all Generally only those parameters which are User accessible are loaded Consequently different users may exchange parameter f
6. lt max val gt lt step gt All items are optional type L lt val gt lt val gt lt val gt While editing the list is in the pop down window Comment Options Any comment or for parameters This value shall appear in the with the O accepts Options Parameter Options field flag initial value of the Options field Notes Unlike full names many of the parameter acronyms are pre assigned conventional meaning and used within the executable file In other words if you change for example the full name or location or default value of F1 nothing bad shall happen If you change the acronym F1 to something else however offset shall stop working Some of the data may be generated and set up during initialization depending upon the type of installed hardware Thus for example the standard Stelar filters have a double list type of input domain constraint but the actual domain script is computer generated during the filter device initialization based upon parameters listed in the Hardware def file This is the preferential way of how the specified hardware can adapt its related parameters Here is a typical parameter definition line SF System frequency 2 3 6 ADWUPF 9 21 R 0 001 120 0 001 MHz Larmor frequency rounded to 001 MHz Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 98 of 98 2 Hardware Definition file hardware def The installation specific Hardware def file defines the hardw
7. 1 c1 V c2 V 2 c3 V 3 where V is the input signal V is the output voltage A is the small signal gain and c1 c2 c3 are small coefficients which should be ideally zero but alas are non zero in practice Their presence leads to the appearance of bothersome combination bands in the spectra Fortunately even the simplest phase cycle alternating additions of positive FID s with subtractions of negative FID s reduce the problem by canceling out the terms linked to the odd coefficients c1 c3 Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 40 of 40 2 7 5 9 Zero Offset Elimination in LR NMR The elimination of zero offset by means of phase cycling is very important in low resolution FFC where evaluation is often done directly on the FID Since the zero signal level is then absolute and independent of any calibration it is not necessary to collect the whole FID Measurements which would be otherwise limited by the zero value calibration e g humidity in solids also benefit in precision by up to 2 orders of magnitude 2 7 5 10 Suppression of the Acoustic Ringing Acoustic ringing is a pernicious phenomenon which can often impair or even preclude successful NMR measurements Source of this acoustic ringing is the mechanical vibration of probe assembly after an RF pulse the effect often leads to audible sounds from the probe hence the name As the probe assembly vibrates at all its mechanical resona
8. Block acronym is NOT equal to LIST the parameter BLST is disabled and the NBLK Number of blocks values of the arrayed parameter specified in BACR Block acronym are distributed between the two extreme values BINI First value and BEND Last value The point BINI is always included when NBLK is greater than 1 BEND is also included When NBLK is greater than 2 the distribution of the intermediate points is Linear if BGRD LIN Linear on logarithmic scale if BGRD LOG Notes BINI may be greater equal to or smaller than BEND In the case of LOG distribution a value smaller than 1e 6 s e g 0 is automatically handled as le 6 To maintain compatibility with evaluation procedures however one should avoid such controversial settings 2 When the value of BGRD Block acronym is equal to LIST the parameters BINI and BEND are disabled and the NBLK values are distributed according to the multi range script specified in BLST List of ranges This script is a list of elementary ranges separated by commas In its simplest form an elementary range may be a single numeric value so that BLST might contain for example 1 1 1 2 4 5 10 However the multi range syntax offers more powerful features also An elementary range may be set up in the form lt first value gt lt final value gt lt grid type gt lt number of points gt where lt first value gt and lt final value gt are numeric values analogous to BINI and BEND
9. I I a O O b When combined with phase alternation 0 and 180 degrees of the excitation pulse phase such procedures lead to the usual advantages of phase cycling but do not mitigate the differences between the two channels In order to achieve this we need to introduce two more ways of signal accumulation receiver phases Receiver I I b O O a Receiver I I b O O a to be used with transmitter pulse phases of 90 and 90 degrees For the simplest sequence S1P the above considerations lead to the following phase cycle of length 4 0 11 2 34 Cycles like this one will compensate exactly for any discrepancy in gain or more generally in amplitude transfer functions of the two channels A partial compensation of phase differences will also occur Note that when one of the two channels is completely missing the above phase sequence will still perfectly compensate for its absence this is the principle of pseudo quadrature detection It is also possible that the phase of the second receiver channel is 90 degrees instead of 90 One can easily verify which case applies by observing a single scan signals with phase settings 0 and 1 respectively If the signals are the same then the second channel is shifted by 90 degrees If however they are of opposite sign it is shifted by 90 degree contact Stelar for further action The most perfect quadrature detection phase cycle permi
10. SW Sweep Width Hz FLTR AF filter Hz and phases of RF pulses 3X Stelar NMR FFC Data Acquisition and Evaluation Package qM Tools 12 Evaluate Hi Hardware gi Configuate 2g5 View Run Help Est Main par Acapar Eval Reports m 2K div Sampe Wae J ntm i ARA Nucleus 1H i Experiment NP S Temperature 25 Acq Data File Gd_testl sdf ep ANERE ee SE EES cep Se Pee EES _ System frequency Observe offset 925 LL 133648280044 Rf attenuation 15 Af gain Recycle delay Maximum T1 1 0 2 0 0582858491469 Delay tau 0 001 Switching time 0 003 BAN A a its Y DoOY Ww NONU EN VN VN X X N N x MN 338324403118 3 38324534133 3 25014724356 Polarization field Relaxation field Acquisition field Imm Mode Start acquisition with current parameters In the Main parameter page couple of new parameters are enabled Maximum T sec TIMX and No of blocks NBLK in ndim in AcqPar page At the same time the parameter Delay tau sec 1s displayed as output The Maximum T sec requires the maximum possible value for the T to be measured This value is used by the program to calculate the different TAU intervals ranging from a maximum of 4 times TIMX to a minimum of 1 ms default values TIMX is also used by the program to set the thermal balancing magnetic field pulses An inadequate val
11. Stelar s r l 2001 Spinmaster FFC 2000 Fast Field Cycling NMR Relaxometer Reference Manual updated to version 1 0 73 STELAR s r l via E Fermi 4 27035 Mede PV Italy Tel 39 0384 820096 Fax 39 0384 805056 info stelar it http www stelar it Stelar SPINMSTER FFC2000 Reference manual Reference Manual for Stelar Fast Field Cycling Relaxometer Contents Page l Ttt OU CE ONG 9 cess ci cA etie e NK a e S eR Mx 1 2 Hatdwates vt ew ores XXI Qr LADEN a a 2 2 1 Overview block diagram and sub units 2 0 0 0 00 000s 2 22 mnstallitioo dates 35 ops e dad TRAE HIIS HATTEN CENA 4 2 5 Switching ON and OFF the relaxometer 0 0000 6 2 4 Spinmaster a Universal NMR console 00 02 ee eee eee 9 2 4 1 Variable temperature controller 44 04 0 e ed cues saddens 10 2 4 2 RF and Digital Dt eds dum era roS Ste Vete E 12 242 L DDSgf fits Los oov Suo ten ox d c RS 13 2 4 2 2 RF transmitter unit i e ee Re Ry Rx rA RR 14 24 2 3 RF receiver nit soeia pes aeq 4 rend dard DUO a 15 24 2 4 AOM Ulo 4 adore erp a ba SEX ECOSSE otis 16 2 4 3 Power supply unit is ite s oe elus ge ea vitu qu dv 17 2 5 Preparing for measurements us yu exe ay TER S VS 20 2 5 1 Prob WINING Loa cue d oos E a ae eG a SA ATA 20 2 5 2 Null current calibration and magnetic field offset 20 2 5 5 Sample temperature setting quos zv e rre rA REN 22 2 5 4 Temperature compensation of Magnet
12. The report generated by the procedure has the following format TAU R Average I Average 2 800e 01 1 187e 02 4 897e 01 2 615e 01 1 359e 02 5 568e 01 When the original data have no imaginary part FTM 0 the result has none too and the I Averages are not listed The terms R Average and Average refer simply to the detector channels A in phase or real and B out of phase or imaginary they do not imply the employment of any phasing algorithm The arrayed parameter whose values are listed in the first column is the one whose acronym was specified in BACR nDim parameters table during acquisition of the data Its values are re calculated using the stored BINI BEND and BGRD parameters When there is just a single block and therefore no BACR parameter the first column heading is null and the value is 0 NOTE When EWIP EWEP the FID window consists of just one point In this case the procedure simply lists the signal values at this point for all blocks of a multi block experiment When graphic output has been specified the WAV procedure produces the DisDat graph original untreated data plus the Multi block graph plotting the window averages against the arrayed parameter values Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 90 of 90 4 4 3 5 Data Window Absolute Magnitude WAM This evaluation procedure generates one real datum for each FID window i e one for each block
13. rf attenuation sweep width 90pulse width etc to get a better FID Before F1 correction on signal Stelar NMR FFC Data Acquisition and Evaluation Package x 4M Tools 12 Evaluate jd Hardware gi Configuate 283 View Run Hep fy Exit T Go o ouit Cont Savel Eg Za Zap Kill Scan 4 eee Main par Acapar Evai Reports HIGIENE EEG SEL TE Song bee eH eH eHeMMRSS Nucleus t Experiment a at ean ea et elie he ole oc Temperature i Acq Data File essaid sdf Se CO E RUPEE LEE LEES System frequency 9 25 Observe offset 15000 Rf attenuation Af gain Recycle delay Delay tau a ee See res eee are ee ee a Switching time Polarization time l Polarization field 10 0006573405 Relaxation field 1 00011896935 p Acquisition field 9 25013015946 Imm Mode Start acquisition with current parameters After F1 correction and RPHS X Stelar NMR FFC Data Acquisition and Evaluation Package ile xvj 4 Tools 12 Evaluate EY Hardware ji Configuate ZS View Run Help Es T Go 9 uit gt Cont E Save Eg Zap Kill Scan JENNI Main par Acq par Eval Reports User Basic Puis Delay nDim Conf Hard Probehead Standard 10 mm Sl deg pulse us B B1 field 8 76415508181 Rix inhibit us 14 Acquisition delay us 6 Receiver phase 269 QD phase setting 90 Phase cycle enable
14. 1s about 160 64 1024 10 ms block Since the recycling delay polarization and relaxation intervals and Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 105 of 105 field switching times normally take up longer all processing except for the flash buffer transfer is done in parallel and all the software overhead we have is just a bit over 1ms per block In classical NMR however situations may arise not very often when most of the time shall be spent in data processing by the AQM In such cases the new AQM appears about 30 40 slower than the old one These are the situations when to use the MUTE mode ii MUTE mode In this mode the scope image on the AQM is not maintained and no graphic data are communicated to the PC during acquisition The User sees a blank screen and just the scan counter goes on at the rate given by DAAP Once the accumulation has stopped however all the data are transferred to the PC and are displayed on the scope This corresponds exactly to what we had with the old system However the maximum processing overhead is now only about 60 ms lpoints twice as fast as with the old device Moreover due to the parallelism it becomes effective only when the theoretical repetition time is lower than 60 ms for larger repetition times the contribution is only 18 ms IKpoints This 1s the absolute minimum for the AQM board and it has nothing to do with AQM to PC communication P
15. Autofilter mode Acq Acc mode Acc parameter CNOT Last modified June 5 2001 Imm Mode Start acquisition with current parameters If signal is not observed on the display one should proceed as follows Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 49 of 49 e Check whether the transmitter is ON e Change the data acquisition mode to Go and Adjust mode and observe the display by varying BACQ parameter by 100kHz at time from 9 5 MHz and to 9 MHz e In the same situation check the position of the probe in the magnet After marking the actual position shift it up and down observing the display window e Check the existence of magnetic field in the magnet Take out the sample and introduce a screwdriver or any ferromagnetic small bar all the time hold with your hand If the magnet is pulsing you should feel the magnetic force shots in your hand If not contact Stelar be sure you are using a ferromagnetic material Now proceed with the help of an electronic expert e Check the output of the transmitter on a 50 ohms load If RF pulse is absent when the Go and Adjust mode is active then contact us e Connect a scope to the SHUNT BNC connector in the front panel of the power supply unit Check that no oscillations are present during the acquisition pulse specially in the second half part If no oscillation is detected measure the value of the pul
16. Do not apply more stress on the glass dewar in the probe i e do not fix the transfer line and probe tightly Either place the transfer line near to the glass dewar gently touching of the probe or leave 0 5 mm gap between these two Tighten the transfer line to the holder using the knob and use the provided metal clip to connect transfer line and the probe dewar Probe Transfer line Holder Transfer line Knob Fig 6 a Liquid Nitrogen Transfer Line Holder Assembly 111 Setting the temperature after 1 or i1 Switch ON the instrument or reset the VTC either by pressing the RESET button or by pressing the keys 1 2 3 simultaneously Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 12 of 12 e The text VTC91 appears on display for few seconds unless one of the following keys is pressed ENT PRT immediately terminates the 5 seconds wait and goes to the temperature monitoring routine 0 1 2 executes Program 0 1 2 if implemented CAL PRG invokes the SPECIAL PROCEDURES menu RST followed by CAL PRG will ask whether to switch over to the TD MATE operating system see the TROUBLE SHOOTING section of VTC manual FOR MORE DETAILS PLEASE REFER TO VTC USER S MANUAL e Press 1 when the message VTC91 appears on the display to set the temperature Next the unit prompts the user to enter the airflow level and set point The heater evaporator starts working after setting the set temperature The set
17. Fig 6 Rear view of VTC Unit Z Thermocouple in 2 Power output to the Heater 3 Evaporator connection 4 AC main power cable Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 11 of 11 We now summarize the operating instructions which are detailed in the separate user s manual for Variable Temperature Controller VTC unit We would like to give brief operating instructions to set the temperature in VTC To operate above and below room temperature two different procedures must be followed 1 Above room temperature Insert the heater into the probe glass dewar and connect the cable to HEATER socket on rear panel of VTC see Fig 6 Connect the dry air or nitrogen gas supply tubes to the appropriate places inlet and outlet and set a correct flow level on the flow meter regulator 11 Below room temperature Connect the evaporator cable to EVAPORATOR socket on the rear panel of VTC see Fig 6 Fill the evaporator dewar with liquid nitrogen Insert the evaporator rod slowly and wait for a while till it reaches thermal equilibrium Secure the evaporator rod with the clamping ring Connect the dewar transfer line between the evaporator and probe Take extra care while connecting the transfer line to the probe because the joint is metal glass First insert the transfer line into the holder as shown in the figure 6 a Adjust the level up and down direction of the transfer line to the probe
18. a data file or press the Kill button to discard the data thereafter the Kill button will become disabled 4 2 4 Macro command mode The macro command mode is entered through the Tools Run macro menu option Macro commands represent a powerful automation feature Once a macro command is launched the system 1 Displays the command name in the top macro panel 2 Disables all the immediate mode buttons except Kill which may be used to interrupt the macro Disables the main menu and even the window s system menu 4 Disables editing of all parameters 2 Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 78 of 78 The User may still inspect parameter tables report sheet XY monitor system log etc but no change is allowed in the parameter As soon as the macro command s execution terminates the system reverts to the immediate execution mode 4 3 5 Evaluation of acquired data An on line numeric evaluation of the acquired data is provided by the Evaluate Evaluation dialog menu command The program displays a dialog where the User can select 1 The data source 1 e a zone in a data file 2 The evaluation procedure to carry out 3 The destination of the results report sheet and or export file 4 An optional export file for the results Once the selections are made and the Execute button of the dialog is pressed the selected evaluation procedure is carried out and the results are sent to
19. always possible even while immediate mode data acquisition is in progress but 2 itis disabled during a macro command execution 3 More complex data evaluation procedures may be implemented as macro commands 4 3 AcqNMR Parameters In this section we will review and comment all the FFC acquisition parameters which are of any relevance to the user We will list all the parameters which could appear in principle Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 79 of 79 In Main parameter page SMPL Sample Name plain ASCII input EXP Experiment type Always accessible Setting a new EXP starts an extensive update of many parameters In particular all Pn and Dn pulse and delay are reset including option switches as well as all parameters related to specialized hardware According to the selected experiment whole groups of parameters may be declared na not applicable others may become active and still others may be enabled disabled for User access TEMP Temperature of the sample This parameter is not interfaced hence it acts like a comment notes FILE Acquisition Data file name Always accessible It enables the file access dialog box and asks the user to enter select the data file name SF Spectrometer frequency reference for the measuring channel When SF is changed the system will update the field of acquisition BACQ according to the current NUC Do not forget that each time you
20. and more flexible electronic methods would have to be applied This implied the development of low inductance air coil magnets and power supplies capable of switching the field electronically to any desired value in a short span of few milliseconds while maintaining the high field stability and homogeneity required by NMR at the same time The approach known as Fast Field Cycling has enjoyed success in several academic laboratories in the past Nowadays this technique is looked upon as an important analytical tool for NMR research and material characterization both in industrial and academic environments Stelar s Spinmaster FFC 2000 Relaxometer is the first commercially available system aimed to attain this purpose As a research grade instrument SPINMASTER FFC 2000 provides the User with both a set of pre programmed experiments and a lot of freedom in designing one s own pulse amp field sequences The classical approaches to measure T at variable field strengths are the pre polarization sequence PP suitable at low relaxation fields and the non polarized sequence NP usable at higher Br x Relaxation field Basic prepolarized sequence BACQ B 0 PW90 PW90 Transmitter Basic nonpolarized sequence Transmitter Acquisition Acquisition TPOL swr TAU swr STIM TPOL swr TAU SWT STIM The upper trace shows the switching of field values between the fixed polarization field Bpol the variable relaxation field Br
21. are linked respectively to the following phenomena 1 probe RF ringing 2 acoustic ringing of the probe 3 acoustic ringing of the sample In all these cases one faces pernicious artifacts which can sometimes impair or even preclude successful NMR measurements The difficulty in dealing with these artifacts stems from the fact that they can not be suppressed by the simple phase cycling sufficient for the elimination of those artifacts which are insensitive to RF phase such as receiver offsets In order to separate a genuine NMR signal from an artifact it is first of all necessary to find a situation in which the two phenomena exhibit different behavior In the case of the receiver zero offset for example it was sufficient to invert phase of the excitation RF pulse good signal changes sign bad signal does not Acoustic ringing is more pernicious since it responds to phase of the RF pulse just like a true NMR signal In order to make it behave differently from the latter at least two RF pulses are needed One method consists of using spin echo there is no acoustic echo to delay the start of acquisition until the ringing dies out This may help but it changes the NMR timing by a considerable amount interferes with relaxation measurements and cannot be used in solids no echo A much better method uses the following trick Suppose that the nuclei is excited with a pulse PW to obtain an FID with the positive NMR signal plus the
22. booting routine is executed before proceeding further This is completely automatic just wait for few seconds If the CI is booted but not updated the current values of the hardware related parameters were so far not transmitted to it the update routine is executed automatically This may take few seconds depending upon the hardware which must be set up The acquisition can actually start only when the CI is updated then it runs in background meaning that most of the system commands e g those of the evaluation menu may execute while acquisition is in progress On the other hand one cannot Modify an essential acquisition parameter such parameters are said to be locked by the active background process Load a parameters file Load parameters from a pre existent data file Issue a new Go or Go and Adjust command which is ignored without warning You may of course interrupt the acquisition process by the specific Quit command Another way which always works but which we do not recommend at all is by re booting the system an action resulting in loosing the acquired data The following actions cause loss of data of an acquisition in progress Switch off either the Host or the Console Interface Reset the Host by pushing the RESET button or by pressing the Ctrl Alt Del combination Resetting the Host via software from another program this monstrous way of terminating execution is not as rare as it should be be
23. cases actually the situation is better since after the sign correction some of the data points may be affected positively and some negatively there shall appear to be a discontinuous step upon crossing zero signal level Consequently fitting procedure such as the one estimating the relaxation rate RSM may end up with a less biased value When the original data were acquired using phase sensitive detection but have no imaginary part FTM 0 the WSM procedure like WAM defaults to WAV and the two procedures become identical A somewhat different case occurs when the data are acquired in diode detection in which case all points are positive already at the detector level and the above procedure would be pointless If such data refer for example to an IR multi block experiment the sign correction is still essential but can be attempted only as a simple guess The applied algorithm in this case is the following 1 Start with the first data block and proceed forward for as long as the data values keep monotonously increasing or decreasing If the whole set is monotonous the data are left unchanged and we have finished Otherwise denote the last monotonous block as b1 and 2 starting from the very last data block proceed backward for as long as the data vary monotonously and denote the last encountered block as b2 unless the data are very noisy we shall have b1 b2 3 Invert the sign of all blocks b for which b lt b1 b2 2 The r
24. change SF you must change tune the spectrometer hardware probe head F1 Observe offset Carrier offset from SF in Hz RFA RF attenuation RF level attenuation in dB GAIN AF Gain AF receiver gain factor T1MX Maximum T1 value in seconds TPOL Polarization time in seconds SWT Switching time of the magnet in seconds RD Re cycle Delay in seconds Time between repetition of experiments TAU Delay tau in seconds Duration of relaxation field BRL X EDLY Echo delay in microseconds Delay between 90 degree and 180 degree pulse BPOL Polarization Field in MHz BRLX Relaxation Field in MHz BACQ Acquisition Field in MHz These field values are specified by means of H Larmor frequency Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 80 of 80 In Acq Par page in User Page USER User ID OPER Operator name MXZN Number of valid data zone in the data file N1 to N4 and AUXI to AUX3 are notes Users can use these columns to write some comments about their sample experiment etc These comments are stored in the data file when you save the data in Basic Page NUC Nucleus A list of nucleus will be displayed when you click this item User can select the nucleus or type 1H 2H 31P etc according to their experiment The chemical symbol input is case insensitive When changing nucleus the acquisition field BACQ value will change automatically according to the Syst
25. ee ae TEMP Temperature 125 i i FILE Acq Data File Tl RII I c System frequency bserve offset Af gain RD Recycle delay 0 2 TAU Delay tau 0 001 SWT Switching time 0 003 TPOL Polarization time 0 23 BPOL Polarization field 9 99924534193 BRLX Relaxation field 1 0001048934 BACO Acquisition field 9 25014724956 aj sokH diw Horizontal scale Once the probe is tuned user should come out of the tuning window by pressing Kill button and the RF cables should be connected for normal operation as shown below Fig 15 Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 57 of 57 Transmitter Out Oo Synt TuneOut ProbeT Ne VA aii Fa ias Fpp x o O PRE IN PREAMPLIFIER Fig 15 RF cable connections for normal measurements Now to update the Spinmaster console either Ctrl U or the Update button in the Hardware menu should be pressed How to decrease the Receiver offset When some offset is observed in the receiver channels A or B or both attempt should be made to reduce the DC offset by turning the potentiometers corresponding to each channel Part no 9 for channel A and 8 for channel B in Fig 10 Follow the procedure given below RF cables connections for normal operation Fig 15 Magnet ON Transmitter ON No sample is placed in the magnet Select Go and Adjust mo
26. evaluation in a single block EWEP End point Final point for the evaluation in a single block EWIB Initial Block Starting Block for the evaluation EWEB End Block Final block for the evaluation for more details about these four parameters see the following section Numeric Data Evaluation Procedure EACN Acronym of 3 Dimension parameter in 3D data PREP Parameters those are to be displayed when selecting a zone in a data file This parameter is actually a configuration structure for the Data File Selection dialogs These are displayed at various occasions including Loading parameters from a data file menu Tools Load parameters from a Data File Selecting a data file amp zone in the Data Evaluation Task dialog menu Evaluate Evaluate data The value of the PREP parameter is a list of parameter acronyms separated by commas which shall be displayed in the Parameters preview window of any Data File Selection dialog When the list is void a blank string all stored parameters of the data file zone are shown When a listed parameter is not found among the stored ones it is ignored remember that parameters with void values and or hidden parameters are never stored in data files PREP itself is not stored in data files but it is listed in parameter files Its value therefore remains unchanged when loading system parameters from a data file but it gets updated when loading a parameter file Copyright Stelar s
27. finally to the ADC digitizer board The digitizer under the hardwired control of a sweep and display controller stores the digitized data in a local RAM buffer called FDB Fast Digitizer Buffer Data present in FDB are displayed in the XY monitor on the graphics window for inspection The local CPU which controls all the CI fetches the data from FDB and moves them over to a soft sector within its own memory buffer The latter is called DAB Data Accumulation Buffer since the CPU adds subtracts the incoming data to from its current contents The display of the accumulated data is not automatic the result can be viewed only at the end of the accumulation when it is automatically copied on to the FDB and hence displayed on the XY monitor Should the accumulated data overflow the 12 bit XY monitor resolution they are automatically normalized this does not happen when the data range is small The accumulated data are available to the Host through a 60K Baud communication link When the Host receives the data it stores them on a disk for further evaluation Wherever they move the data are always accompanied by a full set of acquisition parameters In fact as soon as data are present no essential acquisition parameters may be changed until the data are either discarded or stored on disk During transfer to the Host the data are automatically normalized to 16 bits in order to minimize the propagation of digitization errors 2 7 4 Quadrature Detec
28. front the System Log sheet Parameters options Shows the parameter options full width parameters display Hide options Hides the parameter options Run To run any other external applications like calculator notepad etc Help The Help entry of the main menu contains these commands Contents Opens the run time manual at the Contents page Index Displays the keyword search form of the run time manual About Shows basic features of the program version copyright Exit This command is used to quit the NMR32 program Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 65 of 65 4 2 1 2 Immediate mode buttons The immediate mode buttons are located in the upper left part of the main window just under the window s main menu They are Button Go Starts data acquisition If another acquisition is in progress it generates a warning and does nothing Instead it stops a non critical activity go and adjust digital scope which is underway and then Goes Before starting an acquisition the system tests the current status of the interface and automatically executes the following actions If the Spinmaster console interface CI is not switched ON then a proper error message is issued and nothing more happens the same applies to the cases where an attempt to communicate with the CI fails If the CI is on line but not booted its programs were as yet not loaded the CI
29. loops pulser controlled data acquisition ADC strobes etc A related special feature are the pulser programming registers distinguished by the sign followed by a numeric index 0 1 2 99 These can be assigned numeric values operated upon and more generally appear as arguments in expressions together with constants and numeric system parameters The following directives are currently implemented Directive Action lt index gt lt expression gt Assignment of a pulser programming register lt label gt Target location for the GOTO lt label gt directive lt label gt is any user defined string GOTO lt label gt Unconditional pulser program jump IF relation command Conditional execution of a sequence lt command gt a pulser interval parameter or a directive lt relation gt is a construct of the form lt expression gt lt relation operator gt lt expression gt where relation operator is one of lt gt lt gt lt gt gt lt ZTIMEO Sets the time axis origin for subsequent data points ADC Generates an ADC strobe When at least one ADC is present the experiment type EXPT is set to 1 explicit data points timing array instead of 0 regular timing grid S WEEP Generates a sweeper strobe SETUP Ends SEQUENCE section and starts SETUP section Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 104 of 104 4 Working with the parameters DAAM and DAAP The
30. new parameter DAAM Data Acquisition and Accumulation Mode introduces the potentially rich topic of various data acquisition modes At present it admits two possibilities BASIC which is the mode used up to now MUTE which completely suppresses monitoring of data during acquisition except for the scans counter which remains active In both cases the second new parameter DAAP Data Acquisition and Accumulation Parameter is used to control the rate at which the PC checks the progress of acquisition Its value is in milliseconds and its recommended default value is 200 allowed range is 10 to 2000 The difference between the two modes lies in different timing when scan needs to be repeated very fast and or the data blocks are large To understand the effect consider the various situations which may occur i BASIC mode A When the theoretical time interval between successive scan starts repetition time is larger than the software overhead related to accumulation and or display data transfer to PC the time lost due to data processing is quite small since most of it is done in parallel with pulser amp sweeper actions The actual delay due to software in this case is roughly 18 ms per 1K of complex data points which is the time needed to move data from the ADC buffers to a core AQM memory buffer we call the latter flash buffer This is a plain transfer all more sophisticated processing is done later For comparison with the old AQM
31. r l 2001 Spinmaster FFC 2000 Reference manual page 95 of 95 1 Assuming the value of r to be fixed the formula is linear with respect to a and 5 The optimal values of these two parameters are therefore easily determined using standard linear correlation formulae The resulting optimal values of ai b and Q are then non linear functions of r i e ai a r bi bi r and Q1 Q1 r with Qi r being approximately quadratic around its absolute minimum 2 Using the function which calculates Qi r for any value of r its minimum value can be determined numerically using some standard method in our case the Brendt s algorithm with simple interval bisection Clearly if the minimum of Qi r occurs at r rm then Q Qi ra Q ai r2 bi r2 r2 coincides with the absolute minimum of Q a b r What we have gained is the possibility to evaluate the function Qi r for any r and in particular in the vicinity of the optimum at r2 where we expect it to be approximately quadratic with the quadratic coefficient related to the confidence interval of r Notice that along the curve Qi r Q ai r bi r r the parameters a and b vary dynamically so as to remain optimal for every value of r This is essential since otherwise the error estimates for r would be grossly over optimistic Q Qi r Without dynamic adjustment of a b Numeric values of the confidence interval are based on the least significant increment of Q Assuming that the op
32. ringing due to PW The measurement is repeated but with application of first a 180 degrees pulse Pland then application of PW same width same phase after a short wait time tau and the FID is acquired which now contains three components the negative NMR signal here is the difference in behavior the ringing due to PW and the ringing due to P1 Subtracting the two FID s the ringing due to PW cancels and only the ringing due to P1 is left out The latter may be small if tau is long enough but this has the same drawbacks as echo Whole pair of scans should be repeated but this time with inverted phase of the P1 pulse Since phase inversion of a 180 degrees pulse has no effect on the NMR signal but inverts the ringing due to this pulse summing all four FIDs Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 43 of 43 eliminates all the ringing effects completely moreover tau may be so short that it can be neglected with respect to T a few microseconds are sufficient The reader may have noticed that the above argument applies only if the acoustic response to any series of excitation pulses is linear additive Fortunately this seems to be true to a very large extent In practice the method described above is implemented as follows Use the two pulse sequence S2P Set the width of P1 to 180 degrees and PW to anything you would use normally e g 90 Now specify the phase cycle PH1 40 PH1 00 PH2 40 PH3
33. script consists of a contiguous segment of plain case insensitive ASCII text Its beginning is marked by a text line starting apart from any white space with the keyword SEQUENCE followed by the name of the sequence The sequence script terminates with a text line starting with the keyword END SEQUENCE Individual pulser sequence segments thus appear as text blocks of the form SEQUENCE SequenceName sequence script body END SEQUENCE attention unlike all the rest of the script the keywords SEQUENCE and END SEQUENCE must be in CAPITAL letters Any number of pulser sequences may be grouped together into a single pulser sequences file The only additional requirement on such files is that in order to be recognized by the software their first line must start with the discriminator string STELAR Script File and preferably their file type extension should be ssf standing for Stelar sequences file Apart from the discriminator condition there are no other limitations Any text which does not appear within a SEQUENCE END SEQUENCE text bracket is simply ignored a fact which may be exploited conveniently for comments and or descriptions of arbitrary extension Stelar supplies one pulser sequences file named DefaultSequences ssf which should be located in the same directory as the executable file The software however includes mechanisms for searching and selecting pulser sequences located in text files anywhere in the system
34. section AFLT Auto filter mode This parameter enables disables automatic audio filter settings FL TR DAAM Data acquisition and accumulation mode BASIC the normal mode used MUTE this mode completely suppresses monitoring of data during acquisition except for the scans counter which remains active DAAP delay between acquisition enquiries in milliseconds To control the rate at which the PC checks the progress of acquisition Its value is in milliseconds The recommended default value is 200 allowed range is 10 to 2000 For a detailed description of these two parameters see section 4 in Appendix 1 in Hard page INST Instrument type not accessible BO Larmor field in Tesla The field corresponding to System Frequency SF and F1 B0 SF F1 IOFF Magnet current offset When running relaxation measurements at low magnetic fields the current offset of the magnet becomes very important A high positive offset could limit the minimum Larmor frequency for the relaxation profile to several kHz this will originate an artificial plateau while a negative offset will produce undesired effects on the magnetization For more details please see the section 2 4 2 Null current calibration FOFF Magnet B offset Compensation of background magnetic field For more information please refer section 2 4 6 Environmental Field compensation SLEW Magnet slew rate MHz ms This parameter determines the slope of the Magnet Swit
35. the magnet ON If you start the acquisition with the Magnet OFF you will get the following message Magnet is OFF Should I try to switch ON Answer Y for confirmation and the Magnet Power Supply should switch ON Should the unit remain off press the RESET and ON button E just above the Electronic Power Supply knob B or try one more time starting at point 4 switching ON causes a spike propagating through the mains which can sometimes trip an interlock Should you not succeed take a note of which interlock LED is lighted and consult section 2 6 1 Trouble shooting safety interlock It is also possible to switch the magnet ON manually by pressing the buttons RESET and ON E located at the left side of the Magnet Power Supply and Cooling System unit front panel Check whether the parallel port mode is set to EPP in the BIOS setup Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 7 of 7 9 Turn ON the Temperature Compensation by pressing the green toggle button F on the console please see section 2 5 4 for more details about temperature compensation 10 Switch the RF transmitter ON by pressing in sequence the RESET and ON buttons G located near the AC power switch of RF unit C Spinmaster console 11 Switch the temperature control Unit VTC H ON 12 Select the XY monitor under View menu or hit F9 key in AcqNMR32 program Note If you get an error message as Aqm Device not fou
36. the selected destinations Some of the evaluation procedures such as raw data list may appear trivial However since they convert binary data to a formatted ASCII form they represent a useful way of exporting raw data to external data evaluation programs Estimation of F1 and receiver phase RPHS Select correct F1 using the last data option in Evaluate menu or press Ctrl gt and F6 gt keys together to compute the offset F1 and the receiver phase RPHS from the acquired data In the case of multi block data it averages the results over a range of blocks EWIB EWEB The final data are displayed in the Evaluation page and wherever F1 parameter is listed The FID window which should be used for the calculation as well as the range of blocks which should be used are specified by the parameter EWIP EWEP EWIB EWEB Estimation of T and T Select Evaluation Dialog in Evaluate menu to estimate the relaxation time and rate of a multi block data array under the assumption that the phenomenon is a single exponential decay It accepts only multi block data The calculation is based on the magnitude averages taken over an FID window Statistical evaluation of the result is also carried out and all the results are displayed in the Evaluation page The FID window which should be used for the calculation as well as the range of blocks that should be used are given by the parameters EWIP EWEP EWIB EWEB Notice that 1 Data evaluation is
37. window in Acq Par page and the Tx level in DDS unit Fig 9 Front view of RF power Transmitter Unit IN pulsed zf input from DDS unit OUT amplified pulsed rf output to the probe tuning box BLANK to enable disable transmitter Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 15 of 15 2 4 2 3 RF receiver unit This RF receiver unit is a quadrature receiver with an additional diode detection channel and Programmable Amplifier Filters PAF Signal In 1 REF 90 2 REF0 3 RX ON 4 OUTA 5 OUTB 6 VDC out 7 10 Fig 10 Front view of RF receiver Unit input signal from the pre amplifier probe 90 phase shifted rf reference input from DDS unit 0 phase rf reference input from DDS unit Receiver enable from AQM unit Signal output from Real channel to AQM unit IN A Signal output from mag channel to AQM unit IN B Auxiliary 15 V dc unfused output to the pre amplifier in tuning box 8 9 Z0 trimpots for offset level adjustment 8 and 9 to adjust the DC offset of Channel B imag and Channel A Real respectively 10 sets the DC offset for Diode detection Gain Adj 11 fine adjustment of the imag channel gain it balances gains of the two channels Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 16 of 16 2 4 2 4 AQM unit Acquisition Manager is the heart of SpinMaster It is connected to a sta
38. 000 Reference manual 21 6 iRampiang attifaeis cios et eee e eSI De ea uL E 42 2 1 7 Artayed parameter experiments 5 4 44 es ee trn 45 3 Tutora HOW toze doit aer tod REA tet E E d sesto air Ae 47 3 1 Signal location and conditioning 0 0 eese esses 47 3 2 Relaxation rate measurement at a given field 04 50 3 3 Measuring a complete NMRD profile 0 00 0 0 00a 52 3 4 DO degree pulse calibration 5 euro DE REESE 53 3 goProbed mng uie v d enced Ue c1 ev e cy ese 54 3 6 Writing a simple task script automation 0000 57 3 7 Magnet Temperature Compensation Factor 0 00 58 4 SOL Wale eus debeas aya utis Pat SUP Puff A Ib past EOD PME 60 4 Getting Stans eoe sae suc d aue die suut d PES VIAE EM 60 4 1 1 Computer requirements 2 ducere dae Pe aoe Seow ine RO 61 4 127 vEsSfAl Ta LOB 9 6 doo 3 PN Feo Gs m at Vim ATE arat 61 4 1 3 List of Program files 2045 5 en a OS eR eee den 61 4 1 4 Copyright Agreement 2o ERI de x X a eee 62 42 SoftWare REVIEW oe eu cuo Seres cero ba C oS Pd te s 62 4 2 1 Main WindOW und ees eo e ERA RAE Rae wa 62 22 I Mai Memo us cae 4S PU VERE er him 62 4 2 1 2 Immediate Mode Buttons 0 00005 65 4 2 1 5 Seans Courter caseus eo cR IR Eee ii 66 4 2 1 4 Top Macro panel 2o eere kr res 66 4 2 1 5 Multi page control os cse cueseu eed ae E RUDI 66 4 2 1 6 Overlapped display screens 000005 66 D
39. 20 PH4 Setting 4 amounts to complete suppression of the corresponding pulse and this is exactly what is desired Probe RF ringing NMR probes are almost always constructed as resonant LC circuits Such devices are characterized by a number of parameters the most important of which are resonance frequency matching the nuclear Larmor frequency at the signal detection field and Q factor or quality factor characterizing the sharpness of the resonance band of the probe The whole purpose of using the tuned circuits is to increase the sensitivity Signal Noise ratio of the probe intended as an RF sensor Since the sensitivity is directly proportional to Q the value of Q of a tuned probe is always much larger than 1 In practice it may range from 10 to 200 depending upon the type of samples to be measured solids liquids and or upon the operating frequency The problem with this approach is that the excitation RF pulses do not excite just nuclei but also the tuned RF circuit Once the desired RF pulse is over the circuit keeps oscillating ringing for some time with exponentially decreasing oscillation amplitudes The free oscillations occur at the self resonance frequency of the circuit but their starting phase respects that of the RF pulse whose frequency may be slightly different provided it is within the bandwidth of the probe They thus simulate a genuine signal with a well defined line width and offset The decay rate o
40. 2000 Reference manual page 54 of 54 of the transmitter RF input attenuation TATT 7x base attenuation It should be set to 12 as default Now use the command Go and Adjust in the Hardware menu or by pressing Ctrl F5 to start the experiment Adjust the values of the pulse width using PW90 parameter in the Conf menu under Acq par page to set the maximum FID or increase it until the FID goes to zero to determine a 180 pulse If the resulting width for a 90 pulse is not short enough then decrease the transmitter attenuation TATT and repeat Or as an alternative select ANGLE FFC pulse sequence to determine the 90 degree pulse By default the pulse width is varied from 0 to 31 us in steps of 2 us User can modify these values in Acq par n dim 3X Stelar NMR FFC Data Acquisition and E valuation Package e Tools 12 Evaluate Hi Hardware jg Configurate 2g View Run 9 Help Est Main par Acq par Eval Reports l og oSv User Basic Puls Delay Dim Conf Hard 2D data acquisition Number of Blocks Block acronym Block grid type First value Final value Use right mouse button to popup a menu According to the figure given above the 90 pulse width is 7 us NOTE Please remember to change the pulse width when you change the experiment type from ANGLE FFC to PP or other sequence 3 5 Probe tuning This section gui
41. 94 of 94 parameter specified by BACR for the k th block and a b r are the quantities to be estimated by the multivariate nonlinear fitting algorithm The report generated by the procedure has the following format BRLX RI Zone File 6 001e 02 1 384e 01 4 081e 01 18 filename Notice that the procedure lists the value of the parameter indicated by EACN in this case BRLX also It is up to the user to indicate in EACN a parameter which physically characterizes each set of multiblock data Apart from generating the report the procedure also uses the results to modify the parameters EDF1 EDZ1 EACV ETI ERI ERID and ERIE in the Eval Quick Results table Notes of caution The estimated R1 error interval e resulting from the fit of a single multi block experiment is not to be confused with the r m s scatter in R1 values s when the same experiment is repeated many times Two situations must be distinguished a The decay is truly mono exponential i e any deviation from mono exponential behaviour is much smaller than the experimental noise In this case one expects a strong correlation between e and s with s exceeding e due to experiment repetition statistics and additional error sources statistics alone predicts a factor of about 2 When data accumulation is used both e and s are expected to diminish with the square root of the number of scans b When the decay is not really mono exponential the fitting error e contain
42. A S Stats Bara use 2 eck er ee vtto ird iere bake eh rp die 67 42 2 System Parameters usc Swi ager YET EAE PIA EE CU PTS 67 4 2 2 1 Parameters Review 24 sce RN ee da 67 4 2 2 2 Categories of Parameters 02 2 0 ee eee 68 4 2 2 3 Editing of Parameters aso oy ehe XE SNO bey Eis 69 4 2 2 4 Values of Parameters llslllleseeeesn 70 4 2 2 5 Parameters interdependence 000005 70 4 2 2 6 Pulser interval parameter options 4 71 4 2 2 7 Parameters options syntax 0 0 ee eee eee 75 4 2 2 8 Saving loading Parameters 00 00 eee 76 4 2 3 Immediate Execution Mode 2s e Vn TT 4 2 4 Macro Command Modes amp aus cesis eS shee Caw OE 77 4 2 5 Evaluation of Acquired Data 0 0 ccc eee ee eee 78 43 ACINMR paranieter Se umet gadis wx a qs ania agate ck he aes 78 4 4 Numeric data evaluation procedure else ess 86 4 4 1 Evaluation of Acquired data leise 86 4 4 Numeric evaluation revieW 00 0 c eee ee eee 86 4 4 3 Evaluation procedure et sce e bea dpiee eh ORO CA we 87 4 4 3 1 Evaluation data page essen 87 Copyright Stelar s r 1 2001 Stelar SPINMSTER FFC2000 Reference manual 4 4 3 2 List of raw data LRD 0 0 ccc eee 4 4 3 3 List of stored parameters LSP 0 00 4 4 3 4 Data window averages WAV 000000 4 4 3 5 Data window Absolute magnitude WAM 4 4 3 6 Data window Signed magnitude
43. Configuate Ss View Run Help J Exit ont Gs Sav Z ill Scan Tune probe Eval Reports Center frequency 8250 5 mV div Probehead Standard 10 mm S deg pulse us B1 field 9 786651 00803 Rix inhibit us 13 Acquisition delay us 96 7117988395 Receiver phase 200 QD phase setting 90 Phase cycle enable _ Y Autofilter mode N Acg Acc mode BASIC Acg Acc parameter 200 Last modified June 5 2001 4 E 05 MHz div Vertical scale If the resonance dip doesn t coincide with the base line a thin gray line at the bottom of XY monitor it should be made to coincide with the base line by turning the potentiometer Part no 10 in Fig 10 NOTE If adjustment is done in the potentiometer ie Part no 10 in Fig 10 DC offset in receiver channels A and B should be checked If there is any offset it should be decreased as explained at the end of this sub section Now once again check the tuning If the RFA is very small for ex RFA 20 you get the picture like the following X Stelar NMR FFC Data Acquisition and Evaluation Package 4X Tools 12 Evaluate i Hardware gj Configuate 25 View Run Hep fy Exit T Go Quit gt Gont Sav Za ill Scan Tune probe Center frequency 9 250 i D5V div E Main par Acapar Eval Reports Sample NUC Nucleus 1H i i EXP Experiment PP r t Mt lt e
44. IB and EWEB With old data the procedure can be used to check how far from resonance the signal was and how well was the receiver phase adjusted The arrayed parameter whose values are listed in the first column is the one whose acronym was specified in BACR nDim parameters table during acquisition of the data Its values are re calculated using the stored BINI BEND and BGRD parameters When there is just a single block and therefore no BACR parameter the first column heading is nu and the value is 0 Every time the offset amp phase correction routine is run the results are used to modify the parameters EDF2 EDZ2 EFI EF1S ERPH in the Eval Quick Results table Keep in mind however that EFI and ERPH do not report the corrections but rather the actual corrected values of F1 and RPHS respectively Also in multi block experiments the averages of the offset and phase corrections over all blocks specified by EWIB and EWEB are used to calculate EF1 and ERPH respectively The F1 spread EFIS the difference between the largest and the smallest value of offset correction among all the blocks it is a measure of the stability of the offset varies during the experiment 4 4 3 8 Offset and Phase estimate algorithm Let zk k 1 2 n be an array of consecutive complex data points of an FID taken at times f ti k 1 d where the values of and d are known they can be easily calculated using the absolute index of the first point t
45. PPXRING PPXRING S NPXRING NPXRING S IRXRING IRXRING S PPUB S NPUB S PPIE PPIE S NPIE NPIE S PPCPMG PPCPMG S NPCPMG NPCPMG S IRIE IRIE S IRCPMG IRCPMG S Macros Profile ProfileX ProfilelE ProfileCPMG ProfileIR ProfileIRCPMG Evaluation InspectNmrPar page 106 of 106 Balanced multiblock non polarized sequence without TAU range Pre Polarized sequence using an echo for signal detection balanced multi block version of PPIE Non Polarized sequence using an echo for signal detection balanced multi block version of NPIE Simple Inversion Recovery sequence balanced multi block Inversion Recovery sequence pre polarized sequence with ringing suppression balanced multi block version of PPXRING non polarized sequence with ringing suppression balanced multi block version of NPXRING inversion recovery sequence with ringing suppression balanced multi block version of IRXRING unbalanced multi block pre polarized sequence unbalanced multi block non polarized sequence Pre Polarized sequence using an echo for signal detection balanced multiblock version of PP1E Non Polarized sequence using an echo for signal detection balanced multiblock version of NPIE Pre Polarized sequence with CPMG signal detection multiblock version of PPCPMG Non Polarized sequence with CPMG signal detection multiblock version of NPCPMG Inversion Recovery sequence with echo detection multiblock version of IRIE Inversion Rec
46. The returned value is the average of the magnitudes of all data points which lay within the window as determined by the formula 1X E m PX ib 24 tb k l k l where n is the number of data points in the window and a b are the A channel in phase real and B channel out of phase imaginary components of the signal The report generated by the procedure has the following format TAU Magnitude 2 800e 01 1 300e 02 2 615e 01 1 474e 02 Because of the rectification feature of the procedure the resulting magnitudes may be somewhat contaminated by anomalous noise contribution This is negligible for data with large signal to noise amplitudes When the S N ratio is low however the contribution of the rectified noise to the resulting values may become significant even with zero signal we obtain a non zero value The net result of this systematic bias is a reduction of the estimated relaxation rate The analysis of this problem is a matter of a separate Application Note Like for WAV the arrayed parameter whose values are listed in the first column is the one whose acronym was specified in BACR nDim parameters table during acquisition of the data Its values are re calculated using the stored BINI BEND and BGRD parameters When there is just a single block and therefore no BACR parameter the first column heading is null and the corresponding value is 0 When the original data have no imaginary part FTM 0 the WAM proce
47. WSM 4 4 3 7 Offset and phase estimate 4 0 03 4 224 ene e bre RR 4 4 3 8 Offset and phase estimate algorithm 4 4 3 9 Relaxation rate estimate lllllililsslsses 4 4 3 10 Relaxation rate estimate algorithm Appendix A Pulse sequence script ique a Copyright Stelar s r 1 2001 Parameter definition file parameter def 0 00005 Hardware definition file hardware def 0 0000000 ue Working with parameters DAAM and DAAP 45 Available pulse sequences and macroS 000s eee cece eens Spinmaster FFC 2000 Reference manual page 1 of 1 1 Introduction Ever since the introduction of Nuclear Magnetic Resonance NMR there has been great interest in relaxation phenomena including their field dependence Starting in the fifties mechanical methods for shuffling a sample between locations with different magnetic fields had been used to acquire T dispersion profiles plots of longitudinal relaxation time as a function of field intensity at a constant temperature In such methods a high field magnet is used to pre polarize the sample in order to boost signal intensity thereafter the sample is allowed to relax within a second magnet whose field can be set to any desired value However since mechanical shuffling methods were found unsuitable for fast relaxing samples with 7 values below 100 ms it became evident that faster
48. actual job Following is the list of devices which MUST be defined in the Hardware def file of any Stelar NMR instrument Normally however many other devices subunits of the principal units need also to be defined Thus any type of Aqm assembly Acquisition and Control Manager is likely to contain devices like gt Pulser gt SweepGenerator ADC channels etc This however goes beyond the introductory nature of this Chapter gt Instrument gt Computer gt ComputerLpt gt Sbus gt Aqm gt ObserveTransmitter gt ObserveReceiver gt Magnet gt Lock gt Decoupler Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 100 of 100 3 Pulse Sequence Script Introduction This section describes the pulser sequence programming language employed by the STELAR NMR32 data acquisition program Like in the case of macro commands it is a User and Application oriented fourth generation language 4GL However since the purposes of the two languages are quite different their syntax differs so much that unfortunately any similarity between the two types of scripts stops here The definitions and descriptions which follow are comprehensive but very compact The interested reader is invited to print out and study portions of the file DefaultSequences ssf supplied with the NMR32 package It contains all the pre programmed library sequences many of which can serve as examples A pulser sequence
49. allation plan Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 5 of 5 Mains for Stelar FFC magnet power supply l The magnet power supply of the Stelar FFC NMR Spectrometer has peak power consumptions from 8 kW at 10 MHz H to 20 kW at 25 MHz H Typical average power is much lower but mains must be specified for peak consumption lasting as long as the longest polarization relaxation interval For European Installations the transformer of the magnet and its cooling system should be connected to 3 phase neutral and GND 400 V 50 Hz line The current into the neutral pole is ideally zero and is monitored for proper operations Versions for 3 phases 380 V or 420 V are available If needed isolation transformer may be used as long as it is 3meters away from the magnet It must be capable to supply 22 kW with 3 phases neutral GND Magnet and its cooling system are powered through a single 22 kVA transformer with the primary connected to a 3 phase 400V outlet Spinmaster Console is connected to a standard 220 V 6 A mains Cooling water Maximum temperature 20 C Flow during the peak power consumption 2000 I hr If closed cycle cooling water system is used the minimum pressure difference between inlet and outlet should be 0 7 bar Inner diameter of tap water tube One inch 1 OD 30mm Gas flow for sample temperature control Dry air or Nitrogen gas 1000 I hr 1 to 3 atm Dehumidi
50. an be collected with one phase setting and the resulting FID be saved before collecting another block of MS scans with another phase setting and saving that FID etc these FIDs could be added or subtracted later during data evaluation However this block approach has two disadvantages First in each block the experimental artifacts get accumulated which could lead to memory overflow and thus invalidate the approach For example any offset voltage accumulates linearly and thus limits severely the maximum number of scans that can be collected before the accumulation memory overflows Second during a long accumulation there is a possibility of a slow drift in the experimental conditions temperature field homogeneity which will not reflect in the same way in all the blocks Phase alternation on consecutive scans is therefore superior to the block by block approach This aspect of the phase cycling is called the principle of interleaving 2 7 5 3 Interrupted cycles When the parameter MS maximum scans is set to a value larger than phase cycle length the phase cycle is repeated for as many times as necessary to complete the MS scans Obviously Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 36 of 36 MS should be ideally a multiple of the phase cycle length Sometimes this may be inconvenient or overlooked It can also easily happen that the accumulation is interrupted with NS number of completed scan ra
51. and B are initial and end values of the range T is type of point distribution either LIN or LOG and N is the number of points in the range A and B One can use expressions also in the place of A and B but they should be enclosed by parenthesis Example 0 0 1 LOG 8 0 1 10 LIN 10 OR P1 P2 P3 Pn where P s are points Ex 0 0 1 0 2 0 5 0 9 1 5 2 5 10 20 in Conf page HEAD Probe head Type code of the used probe head This is just a note PW90 90 degree pulse width Duration of 90 degree pulse in microseconds PDMx Phase Diode detection Select P for phase detection mode or D for diode detection FTM Fourier Transform detection mode Always accessible Allowed values 1 0 1 FTM is used to specify the detection mode When FTM 0 which is the default value the quadrature detection is used while FTM 1 or 1 indicates the use of a single detector channel In the later case there is no difference in the acquired data for the two settings they are used only in the data evaluation routine to achieve proper orientation of the spectra The logic behind the three values is linked to the carrier frequency with respect to the spectrum indicates that the carrier is at the left border of the spectrum high carrier offset low field 0 indicates that the carrier is at the centre of the spectrum and thus implies the use of quadrature detection 1 indicates that the carrier is at the right border of the spectrum low carrier
52. are structure of the instrument It is a crucial element of the NMR32 package which must be present in the same directory as the executable AcqNMR exe file When absent the program shall issue a warning and terminate before completing its initialization The file contains plain ASCII text and therefore can be edited by any suitable plain text editor However since the information contained therein is critical in the sense that unqualified modifications would almost certainly preclude proper functioning of the system and possibly endanger some of its hardware Stelar strongly discourages Users from editing this file unless they are Stelar trained to do so and have discussed any intended modifications with the Company prior to applying them Users shall be held directly responsible for any negative consequences of violating this rule In any case before you incorporate any changes make a copy of the original file so that you can restore it if anything goes wrong Syntax rules The file contains only plain ASCII text Lines starting with gt where is a device name contain device definition scripts All other lines are ignored comment lines Each elementary device definition takes up one line of script The definition scripts for all devices listed below are required even when the corresponding device is not installed see below Additional devices may be required depending upon the type of the principal units
53. artifacts such as DC offset coherent spikes pulse width amp phase misadjustment etc However the use of phase cycling as a filter for genuine NMR components soon became apparent and proved to be a major success examples elimination of a contaminating spin echo from an FID extraction of a particular multi quantum coherence This concept has eventually been extended even further in order to accommodate cyclic variations not just in the transmitter and receiver phase settings but also in other acquisition parameters and or hardware device states The most notable examples include sequence with sophisticated management of decoupler states in HR NMR or sequences involving different settings of a generic X device such as the magnet in Fast Field Cycling relaxometry Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 34 of 34 2 7 5 2 Basics of Phase encoding In a one pulse sequence the phase of the pulse can take on any value between 180 and 180 degrees all RF phases are ofcourse referred relative to the receiver reference phase The most common settings are 0 and 180 degrees and when quadrature detection is used 90 and 90 degrees In the literature these values are often denoted by alternative symbols The most common notation supported by the NMR32 program is x x y and y respectively Basic values of the accumulation signs Add Subtract in phase detection Add in diode detecti
54. ation task definition dialog The procedures can be divided into two categories 1 Procedures applicable to any data set LRD List of raw data LSP List stored parameters WAV Data Window Average s WAM Data Window Signed magnitude s WSM Data Window Absolute magnitude s Offset and Phase estimate s 2 Procedures applicable only to multi block data sets RAM Relaxation rate estimate using WAM procedure RSM Relaxation rate estimate using WSM procedure RAV Relaxation rate estimate using real WAV T2M Ty estimate using magnitudes T2R T estimate using real part All evaluation procedures operate on the data subset specified by the data window parameters The procedures listed in category 2 also make use of the parameter EACN Evaluation Acronym The value of EACN does not affect calculations it just specifies a parameter which characterizes the whole multi block data set e g the relaxation field BRLX The value of the latter is listed in the evaluation procedure s reports together with its principal results 4 4 3 1 Evaluation Data Page The data window or data subset is defined by means of two pairs of parameters within the evaluation parameters table a EWIP and EWEP Evaluation Window Initial Point and Evaluation Window End Point respectively define a section of each FID data array to be used don t get confused by the term window which in this case refers to a secti
55. be should be observable unless it is outside the displayed frequency range If the mismatch line goes above the upper border of the window change the gain to increase or decrease the RF attenuation RFA in the Main parameter page If the resonance dip is not observed increase the frequency span in the XY monitor lower left hand corner Example In the following fig the resonance dip is far away from the center frequency ie SF X Stelar NMR FFC Data Acquisition and Evaluation Package KJ Tools 12 Evaluate Hi Hardware dg Configurate ZS View Run Help E Exit ia it C Savel Eg Zap Kin VP Tune probe Center frequency 10 000 Sample 7 Nucleus 31P Experiment S1P Temperature 25 Acq Data File System frequency 10 Observe offset 104963891441 Af attenuation 35 Af gain 1 Recycle delay 0 2 3 5 MHz div Use right mouse button to popup a menu Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 56 of 56 Now use the tuning and matching knobs on the probe to position the dip at the desired central frequency and make it as profound as possible a 20 dB dip is acceptable but try to get as much as possible as shown in the following figure You can expand and reduce both the horizontal and vertical scales 3X Stelar NMR FFC Data Acquisition and E valuation Package 4X Tools 12 Evaluate Hi Hardware i
56. ble sounds from the probe hence the name As the probe assembly vibrates at all its mechanical resonance frequencies the BO flux though the receiver coil oscillates and generates a signal which has nothing in common with NMR For the receiver to pick up the signal it must contain Fourier components with frequencies close to the operating frequency For mechanical vibrations this is less likely at high frequencies than at low ones especially since we anyway talk about high frequency ultra sound waves 1 20 MHZ propagating through the probe materials in particular those used to provide mechanical support for the probe The signal induction process presumes also the presence of magnetic field so that we expect the phenomenon to be more pronounced at high fields than at low field More rigorously it is possible to show that the problem grows with the square of the ratio of field intensity to the operating frequency which amounts to saying that it correlates with the inverse square of the gamma ratio of the measured nuclei In practice it is usually negligible for nuclides with high gamma such as proton or fluoride but becomes often prominent for low gamma nuclides such as deuterium The recognition of the acoustic probe ringing artifact can be made using the following criteria 1 The signal is independent of the presence of the sample 2 It disappears when the magnetic field is switched off or the probe taken out of the field this distingui
57. ce manual page 28 of 28 VTC FUSE AC mains T2A power supply 5x20 F1 F2 F3 F 1 6A Variable 5x20 Temperature Control FUSEHEATER F63A Unit EVAPORATOR 5x20or 6 3x32 Magnet field cycle Illogical results may suggest that the magnet field cycle does not correspond to the program sequence Check at the shunt monitor connector using a scope whether the magnet current corresponds to the programmed cycle If it does not check the reference monitor keep in mind that in this case the signal is inverted If the reference corresponds to the programmed cycle then some problem could be present in the FIELD REGULATION board or in the power supply In this case call Stelar If even the reference does not correspond to the programmed cycle check all connections between the PC and the Power Supply unit Reboot the system if necessary If the problem persists call Stelar Noisy relaxation curves at low fields If the relaxation curve becomes non exponential at low fields or the last points of the profile become noisy and or scattered check the offset current and B offset Check slew rate and switching time settings Check possible oscillations or instabilities in the magnet current shunt connector MOSFET Testing If the MBF interlock is enabled a few MOSFETs might have gone bad If the positive arm of MOSFET or one of its two fuses is broken at a field level of 6 MHz H or more then the corr
58. ching pattern MTCF Magnet Temperature Compensation Factor Hz degC For further details please refer section 4 9 Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 84 of 84 SSPC Pulser Channels PCPM Pulser Polarity mask TXEN Tx enable channel used to enable the power output of final RF boosters PINC Phase increment channel used to advance DDS phase amp attenuation stack address The above four parameters are not accessible TATT Transmitter base attenuation This changes the amplitude of pulsed RF input to the transmitter The default value is 18 If your 90 deg pulse length is not short enough decrease this TATT value in Evaluation page in quick results page sheet EDF1 Data file name EDZ1 Data zone Number of the evaluated data zone EACV Brelax MHz Value of the parameter specified in EACN ET1 T sec Value of Relaxation time ERI R 1 T sec Relaxation Rate ERID Error in R Absolute error in Relaxation Rate ERIE Error in R Relaxation Rate and T1 relative error EDF2 Data file EDZ2 Data zone Number of the evaluated data zone EF1 Fl estimate Hz Mean value of the Signal Offset EFIS F1 spread Hz Maximum minimum offset value for multiblock data only ERPH Rx phase estimate Estimated Receiver phase mean value from the acquired data in Parameters page sheet EWIP Initial point starting point for the
59. cific and indicate the presence of a particular hardware The file contains plain ASCII text and therefore can be edited by any suitable plain text editor However since the information contained therein is critical in the sense that unqualified modifications could preclude proper functioning of the system and even endanger some of its hardware Stelar discourages Users from editing this file unless they are quite experienced and clear any intended modifications beforehand with the Company Users shall be held responsible for any negative consequences of violating this rule In any case before you incorporate any changes make a copy of the original file so that you can restore it if anything goes wrong Syntax rules The file contains only plain ASCII text Within the file the significant section starts with a line beginning with gt Parameters and ends with a line beginning by gt usually gt End Anything before and after such a section is a comment Each parameter definition takes up one line The order in which the parameters appear may be relevant in some contexts e g Updating Extra white space blanks tabulators empty lines is ignored Lines starting with a vertical bar are ignored comment line Each parameter definition line contains the following items separated by Item Description Note Acronym Brief reference name 1 4 characters usually capital letters and digits Full name Extend
60. d that 1 only currently accessible parameters classified as pulse intervals shall be accepted and ii the value of the specified arrayed parameter is now handled automatically and cannot be changed manually 3 Specify the arrayed parameter s range s click the link to see detailed instructions The resulting multi block experiment being defined exclusively through the standard pre defined system parameters can be still run within the immediate execution mode It thus represents the lowest automation level level 1 Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 46 of 46 All the multi block parameters get written into saved parameter files as well as into data files and are restored back upon loading parameters from any of the two sources In this way all your modifications can be easily saved and subsequently reloaded when needed Naturally the DefaultSequences ssf file contains many ready made multi block sequences usually but not always containing the postfix S in their name If you wish you can convert these back to single block sequences by setting NBLK 0 and checking whether the value of the originally arrayed parameter is what you want once NBLK is null the parameter becomes again editable by hand Arrayed parameter ranges The range of values of an arrayed parameter can be specified in several ways illustrated here is the example of multi block experiments 1 When the value of BGRD
61. data are such that off line evaluation programs sometimes written ad hoc by the User are quite common Despite this fact however the NMR32 package includes a number of on line data evaluation routines The reasons for including such procedures are multiple a Data export Data export to external programs is of course a must One can always export raw data but often it is preferable to subject them first to a partial application neutral pre processing e g exporting magnitudes of the signals rather than the in phase and out of phase components b Routine measurements It turns out that in any branch of NMR some 90 of data processing are standard and can be covered by very few well defined routines while the remaining 10 are spread over a vast number of non standard evaluation procedures Having the standard routine s available on line within the framework of the data acquisition program is practical c Experiment optimization Even a preliminary evaluation may be extremely useful when one tries to optimize the data acquisition parameters for a particular sample In NMR relaxometry for example an approximate knowledge of the actual relaxation times is essential for proper settings of acquisition parameters Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 87 of 87 4 4 3 Evaluation Procedure A run time list of the currently available data evaluation procedures appears in a list box of the evalu
62. de Expand the vertical scale in the XY monitor 16 div or 8 div Select Channel A in the XY monitor bottom Right Hand side The noise level should coincide with the base line If not turn Part no 9 in Fig 10 to reduce the offset Select Channel B in the XY monitor The noise level should coincide with the base line If not turn Part no 8 in Fig 10 to reduce the offset 3 6 Writing a simple task script automation In this section we explain how to write an automation program using Macro commands Macro commands are prepared independent of the application program e g using a text editor and saved in a macro commands file This is certainly the most powerful method Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 58 of 58 permitting full exploitation of the macro commands metalanguage as well as a number of non orthodox tricks forbidden to a generic user If you want to follow this approach however read the chapter Introduction to macro commands and keep in mind that a Macro commands are in fact high level language programs Therefore they must be carefully checked and tested before use b STELAR is not responsible for whatever errors you might commit in your own macros We supply a number of tested pre prepared macros in special file DefalultMacros SMF These macro command libraries are intended to grow continuously as a result of customer requests as well as our own initiatives ask pe
63. des the user to tune the probe for a desired acquisition frequency very easily with the help of software program To start tuning first operating frequency of the probe should be defined To do it set the desired value for the parameter SF system frequency in MHz in the Main parameter page It is also needed to select Q for the probe depending on the sample signal property switch located at the probe Set the following values Nuc 1H SF 9 25 MHz RFA 35 Note data acquisition is done at the same field in the case of H corresponding to the resonance frequency of the probe ie SF Next connect the cables including the correct A 4 cable for probe tuning at the preamplifier box as shown in the following figure Fig 14 Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 55 of 55 Synt Sig Out Probe Transmitter Out Power supply 9 GATE PRE IN 9 PREAMPLIFIER Fig 14 RF cable connections for Probe Tuning During tuning only the tuning box is used the pre amplifier is bypassed Now from the hardware menu of the AcqNMR32 program select Tune Probe The graphic data display window on the right side in the Main window of AcqNMR32 will display the probe mismatch function in dB 10 dB per vertical division as a function of frequency the horizontal scale The central vertical line corresponds to the current System Frequency SF in Main parameter page The resonance dip of the pro
64. dified Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 86 of 86 4 4 Numeric Data Evaluation Procedure 4 4 4 Evaluation of acquired data An on line numeric evaluation of the acquired data is provided by the Evaluate Evaluate data menu command The program displays an evaluation task definition dialog where the User can select 1 The data source i e a zone in a data file 2 The evaluation procedure to carry out 3 The destination of the results report sheet and or graphic sheet 4 An optional export file for the results Once the selections are made and the Execute button of the dialog is pressed the selected evaluation procedure is carried out and the results are sent to the selected destinations Some of the evaluation procedures such as raw data list may appear trivial However since they convert binary data to a formatted ASCII form they represent a useful way of exporting raw data to external data evaluation programs Notice that a Data evaluation is possible even while immediate mode data acquisition is in progress while b it is disabled during a macro command execution c More complex data evaluation procedures can be implemented as macro commands 4 4 3 Numeric Evaluation Review It is evident that in principle a data acquisition package is not responsible for the subsequent evaluation of the acquired data In NMR in particular the types and the complexity of the acquired
65. dure defaults to WAV In many applications this makes it possible to use the same procedure to generate valid intermediate data for all acquisition modes quadrature phase detection single channel phase detection and diode detection When graphic output has been specified the WAM procedure produces the DisDat graph original untreated data plus the Multi block graph plotting the window magnitudes against the arrayed parameter values 4 4 3 6 Data Window Signed magnitudes WSM This evaluation procedure is like WAM data window absolute magnitudes except for an a posteriori attempt to determine the sign of the signal In particular this becomes a necessity when upon stepping of the arrayed parameter the signal changes sight a typical example is the IR sequence In the case that the data were acquired using quadrature phase detection the estimate of the actual sign of the signal is carried out as follows Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 91 of 91 1 First the data block wi th the largest absolute magnitude is chosen as reference 2 For any other block one calculates the signal correlation coefficient for the two blocks i e c Y wa ib a ib Yw k l k l where the apostrophe indicates the reference data the asterix denotes complex conjugate and wk are suitable positive weight factors at present wk 1 The discriminating quantity is the real part of c when it is pos
66. e Users should never do so themselves The basic components of a system parameter are Name A long descriptive name of the parameter Acronym A brief name at most four characters used to refer to the parameter in situations where long descriptive names are not acceptable pulse sequence scripts macro commands scripts data files parameter previews etc Value Current value of the parameter This may be a number or a string Moreover some numeric values may be defined indirectly by means of an arithmetic expression involving other parameters as arguments Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 68 of 68 Comment or Options This is usually a comment string containing a brief description of the parameter In some cases however the string is defined at run time by the system and or by the User and affects the operation of the instrument 4 2 2 2 Categories of parameters There are many parameter attributes according to which parameters can be classified A typical User however needs to distinguish only the following categories they are not mutually exclusive a parameter may belong to more than one category Accessible parameters Inaccessible parameters Hidden parameters Pulser interval parameters File parameters Accessible Parameters The value of an accessible parameter can be edited at run time When User clicks an accessible parameter s name its background chang
67. e 41 of 41 The reader may have noticed that the above argument applies only if the acoustic response to any series of excitation pulses is linear additive Fortunately this seems to be true to a very large extent In practice the method described above is implemented as follows Use the two pulse sequence S2P Set the width of P1 to 180 degrees and PW to anything you would use normally e g 90 Now specify enable the phase cycle PHCY The setting 4 amounts to the complete suppression of the corresponding pulse and this is exactly what is needed The sequence has been pre programmed in AcqNMR under the name PPXRING NPXRING etc Following the same general principle as above other more complex sequences have been included which permit more sophisticated measurements relaxation times etc similar to be done in the presence of acoustic ringing 2 7 5 11 Phase Cycle Filters for Genuine NMR Components This category of phase cycling applications is by far the most rewarding genuine signal components can be untangled from each other but at the same time the most complicated from the theoretical point of view It has become the essence of multiple quantum NMR spectroscopy as well as of an amazing number of applications dealing with the coherence transfer in coupled nuclear systems We cannot do much more here than refer the reader to NMR literature dealing with the topic However in order to illustrate the principle we shall consid
68. e Spinmaster check that the computer is not blocked Interlocks If one or more interlocks cannot be reset or is are activated without any apparent reason there may be an internal failure Call Stelar Fuses If one or more voltages are missing at the POWER SUPPLY unit located at the front panel of the Power Supply rack see LEDs in its front panel one or more fuses could have got blown To check open the front panels of the power supply and replace the blown fuses see the figure given below Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual Details of Fuses used in Spinmaster FFC 2000 Fuse No Rating Location FUA FU5 T2A Control Unit Panel FU6 TIA 5x20 or 6 3x32 FUI FU2 FU3 T3 15A lt 5x20 FU7 FU8 FU9 T3 15A Power plane FU10 FU11 FUI2 T 16A CERAMIC F1 F2 F4 T2A F7 F8 F9 T 50mA F5 F6 T250mA Power Rack Main F10 F12 TIA Board 5x20 F3 T 3 15A F11 T4A FH1 FH2 F 0 5A Control Unit Back Plane 5x20 F1 F3 T 1A Cooling System F2 T3 15A Main Board 5x20 32 FUSE FUI F 50mA 5x20 MOSFET Driver 31 FUSE FU2 20A AUTO FUSE FU2 3A SPINMASTER CONSOLE FH8 FH9 T2 5A FH6 FH7 T 0 5A Power Supply Main FH4 T 10A Board 6 7 FH2 T 6 3A 5x20 FHI T4A 5x20 or 6 3x32 FH3 T2A FH5 T 5A 6 3x32 Copyright Stelar s r l 2001 page 27 of 27 Spinmaster FFC 2000 Referen
69. e brackets are copied into its options field when the sequence is loaded again this does not preclude subsequent changes When any of the optional items is missing its current value is left unchanged In order to understand properly the initialization process keep in mind that upon loading a new pulser sequence but prior to any script driven initialization the system takes the following actions a Resets number of blocks parameter NBLK to zero b Clears option specifications of all pulser interval parameters c Restores original display amp access flags of all parameters according to the original specification in the file Parameters def d Hides all pulser interval parameters During the initialization process the hidden flag of every encountered parameter including the ones appearing within expressions is automatically removed The rule is that when a parameter is used it should be displayed regardless of whether it is User accessible or not unless of course its display location in the file Parameters def is null The ZSETUP section includes the parameter ENDS with the initial settings of the receiver phase cycle almost always Example of a ZSETUP section DO RD PW 90 p x x y y ENDS p x x y y Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 103 of 103 Sequence section The sequence section of a pulser sequence script is scanned every time the virtual pulser is prog
70. e enough Make sure you see the resonance signal and not a Nyquist sideband by temporarily reducing the AF filter aperture AF filter Hz FLTR to about 10000 Hz the persistence of signal proves the correctness of the signal Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 50 of 50 9 If the resonance offset F1 exceeds 450000 Hz compensate it by varying the acquisition field BACQ Note that in order to decrease F1 by a given amount you must increase BACQ by the same amount For example if you want to move the offset 7000 Hz down you must increase BACQ by 0 007 it is in MHz 10 You should now have a signal which is close to resonance with F1 comprised between 5000 and 5000 Hz 3 2 Relaxation rate measurement at a given field In this section we describe the general procedure to evaluate T using multi block NP S and PP S sequences First decide the field at which you want to do the T measurement and enter this value in BRLX filed in the Main parameter page Then check for the default values in the appropriate columns as described in Section 3 1 basic parameters setup Then optimize all parameters concerning switching time RF transmission receiver and acquisition using the PP or NP sequence Receiver gain can be specified through Rf attenuation RFA and Af gain GAIN in the Main parameter page Set acquisition parameters BS scan size and SW sweep width and the AF filter FLTR to your be
71. e in order to generate the proper sequence of pulser steps Notice that while the setup section is scanned only once just after changing the parameter EXP the sequence proper section is scanned every time the pulser needs re programming which happens quite often However this does not imply re opening its source file since the sequence script is stored in RAM Setup section The setup section of a pulser sequence script is scanned just once when loading a new experiment parameter EXP The order in which its individual items appear is not particularly important except in special cases Each of its commands consists of 1 A parameter acronym followed by the following optional items 2 Parameter User access configuration consisting of one of the following characters enable User access disable User access space don t modify 3 Initial value to be set when the sequence is first loaded remember that subsequently the value of the parameter may still change A plain numeric value may be specified either directly as a number any format or as a string constant e g 23 Values may be initialized also to expressions in this case they must be enclosed in parentheses and follow the expression value syntax rules String values must be enclosed in quotation marks 4 Initial settings of pulser parameter options This item if present must be enclosed in square brackets When the parameter is a pulser interval the contents of th
72. e input signal level to the final transmitter booster It then depends upon the latter unit s class A B C and linearity what the output pulse RF amplitude shall actually be With most class C transmitter boosters the non linearity is quite strong and the transition from completely OFF to completely ON occurs within a limited range of some 12 dB the purpose of the TATT parameter is in fact to adapt the transmitter input level to its opening threshold If you need to know quantitatively the correspondence between the attenuation level settings and the actual output power you should pre calibrate them iii Pulser channels switch The pulser channels switch is an intrinsic pulser controlled device which may appear in pulser interval parameters options with the pre defined device identifier c As such it may take part in data acquisition phase cycling Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 73 of 73 The c device option arguments may be strings of letters each of which specifies a combination of pulser channels which should be made active during the specified interval iv Receiver Phase The special parameter ENDS End of sweep located at the bottom of the Acq par Delays parameters table is somewhat anomalous since a its value is irrelevant and inaccessible b it accepts option specifications like a pulser interval parameter but C it does not correspond to any actual time interval within a pulse e
73. e therefore needs at least two RF pulses One method consists of using spin echo there is no acoustic echo to delay the start of acquisition until the ringing dies out This may help but it changes the FFC timing considerably interferes with relaxation measurements and cannot be used in solids no echo A much better method uses the following trick Suppose that the nuclei is excited using a pulse PW to obtain an FID with the positive NMR signal plus the ringing due to PW The measurement is repeated but this time first a 180 degrees pulse P1 is applied and then apply PW same width same phase after a short time tau to acquire the FID which now contains three components the negative NMR signal here is the difference in behavior the ringing due to PW and the ringing due to Pl Subtracting the two FID s the ringing due to PW cancels and only the ringing due to P1 is left out The latter may be small if tau is long enough but this has the same drawbacks as the echo What must be done is to repeat the whole pair of scans but this time with inverted phase of the P1 pulse Since phase inversion of a 180 degrees pulse has no effect on the NMR signal but inverts the ringing due to this pulse summing all four FIDs eliminates all the ringing effects completely moreover tau may be so short that it can be neglected with respect to T a few microseconds are sufficient Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual pag
74. e user can set the window on the data point for evaluation EWIP EWEP EWIB EWEB 7 pna lstpt T 2700 dNP in PP Istpt t The magnetization recovery for NP and PP sequence is shown in the above figures If default phase cycling setting is being used a multiple of 4 scans is recommended in order to make full use of the desired effect 3 3 Measuring a complete NMRD profile Profiles can be measured in manual form using NP S and PP S or NPX S PPX S etc However the program includes a set of macros to run automatic profiles To run a macro first all parameters need to be set A possible general procedure is described below Set the correct temperature of the sample Use the NP or NPX sequence to set all parameters concerning the magnet cycle switching times slew rate pre scan delay etc RF receiver gain 90 pulse width etc and acquisition scan size spectral width etc at the maximum desired Larmor frequency of the profile Check the need of temperature compensation and set it if necessary For long relaxation times care is needed in setting the appropriate duty cycle to avoid working at extreme temperatures or measurement interruptions due to interlock interventions Check the current IOFF and Bo FOFF offsets if the profile is extended up to 10kHz or less Load the NP S or NPX S NPx S etc depending on the macro to be used sequence and check parameters Define data and results files Mea
75. ed name displayed in tables any string Display page Index of parameters display table 1 9 0 means don t display Location Location index within the page 1 18 0 means don t display MainLocation Location index in Main Pars page 1 18 0 means don t display in the Main Pars page Flags A string of letters which may include A User accessible I Integer number F Floating point real number Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 97 of 97 S string value S string in CAPITAL letters only B MultiBlock parameter C may be computed through a formula V Admissible as a variable in expressions D affects Data E Evaluation parameter save only in parameter files H Hidden unless enabled in a sequence P rf Pulse p affects pulser timing T pulser Timing delay U Update upon loading unless hidden W Write into parameter and data files O accepts Options Value Default initialization value Initial default values must be mutually coherent Domain type Describes the input constants type RLLIDN otherModifier letters R Range L List L1 Implies that only the listed values can be accepted D Double list N other No constraint Modified letterThese are optionalallowed with RLD u Round to nearest upper admissible value up d Round to nearest lower admissible value down n other Round to nearest admissible value nearest Domain script Defines the input constraint values Syntax depends upon Domain Type type R lt min val gt
76. editing history of the parameter i e a certain number of values which were input recently by the User This is helpful since it often happens that one wants to return to a previously used value Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 70 of 70 Many numeric parameters are limited to either integer values and or to an allowed range of values For such parameter whatever value is input it is always checked and if illegal the nearest allowed value is automatically chosen 4 2 2 4 Values of parameters The parameter value is a string which depending upon the particular parameter is interpreted either as an alphanumeric string or as a number The value may be subject to editing constraints see parameters editing which apply also when the parameter is set from a macro command The length of RF pulses PW90 P1 to P16 are expressed in degrees of the nutation angle and converted into times before downloading to the pulser using the current 90 degrees pulse width PW90 as conversion factor If PW90 is 5 us and P1 is set to 180 degree its length is 10 us The pulser interval parameters represent a special case Their values are inherently numeric but unlike other parameters they admit an indirect definition by means of an arithmetic formula For example D2 may be set to 2 D1 to keep D2 twice as long as D1 The formula is evaluated during virtual pulser programming virtual pulser is a software ima
77. elar OC II Magnet Over current First over current sensor Reduce current Contact Stelar MOT Magnet Over Temp Reduce duty cycle Contact Stelar OCI Magnet Over current Second over current sensor Reduce current Contact Stelar PL Phase Lock One or more AC input phases are dead fuse MBF MOSFET Bank Failure There are too many burned out transistors Replace them PF Program Failure The Spinmaster Console is most probably OFF Heat sink fan is located at the left side in the bottom of the Power Supply amp Cooling System rack Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 25 of 25 2 6 2 Maintenance a Cooling fluid refilling The FFC magnet is cooled by a costly cooling fluid called GALDEN D80 boiling point 80 C produced by Ausimont SpA Italy The fluid though very heavy 1 75 kg l has quite low viscosity and high vapor pressure Consequently even though the cooling circuit is sealed minor losses may occur and it is necessary to compensate for them with periodic refillings The cooling liquid level can be easily checked just by looking at the cooling liquid tank through the glass window provided for this purpose Looking inside from above the level can be easily checked The position of the opening for refilling is shown in Fig 3 J During a refill the Cooling System must be switched OFF Use a clean plastic funnel the cooling liquid is chemically inert and reduce the time
78. em Frequency SF NS Number of actually completed scans Inaccessible from the keyboard maintained by the system This parameter indicates the number of scans which have been completed during an acquisition MS Maximum number of scans Always accessible Allowed values are 0 to 2147483647 ie 2 1 This is the maximum number of desired scans After a data acquisition has been started it proceeds until it is either interrupted by the operator or until MS scans are completed If MS is set to 0 the acquisition proceeds indefinitely and can be stopped only by the operator When setting MS the acquisition time TTIM is recalculated DS Dummy scans Dummy scans are useful to pre establish the thermal cycle of the magnet before starting acquisition They are very important when using short recycle delays RD and a high number of scans BS Block Size Number of data points in a single block BS must be a power of 2 its minimum value is 2 in single detector mode and 4 in quadrature detection The maximum value is 32768 32K In quadrature detection FTM 0 BS is split into halves one reserved for the in phase real data and the other for the out of phase imaginary data STIM Sweep time This sweep time is calculated from the block size BS and sweep width SW During this time magnet is in Acquisition field SW Sweep width Spectral window width in Hz Nyquist frequency The maximum range is 10MHz In practice SW de
79. ent Contact Stelar probably internal defect Tmax Excess temperature Contact Stelar probably internal defect SWR Standing wave ratio not used in this version DUTY Duty cycle not used in this version e Cooling System LEDs located on the front panel of Magnet Power Supply right side Interlock LED Recommended Action Note Tap water pressure Cooling liquid pressure Make sure tap water is open and the pressure is sufficient Check whether the pump is working Contact Stelar Cooling liquid level Cooling liquid temperature Add cooling fluid to the system Contact Stelar this should never happen Note the cooling liquid pressure LED is always ON when the pump is not running e Magnet Power Supply LEDs located on the front panel left side Interlock Meaning Recommended Action Note LED CS Cooling system Check cooling system interlock status four interlocks ML Cooling liquid level not used implemented on cooling system CLP Coolant low pressure not used implemented on cooling system BOTI Bank 1 Over Temp MOSFET bank 1 overheats Check hoses Contact Stelar BOT2 Bank 2 Over Temp MOSFET bank 2 overheats Check hoses Contact Stelar BOT3 Bank 3 Over Temp MOSFET bank 3 overheats Check hoses Contact Stelar BOT4 Bank 4 Over Temp MOSFET bank 4 overheats Check hoses Contact Stelar BROT1 amp 3 Bridge Rectifier Over Temp Check if heat sink fan is working Contact St
80. entration and acidified with HCl to PH 2 will be suitable Otherwise use a sample with T at 8MHz no longer than 30ms and with a nice and long liquid like FID Sample tube diameter 10 mm Volume of sample 1 ml 2 Switch ON the relaxometer as per the instructions given in Section 2 3 page 7 3 Place the sample in the magnet hole taking special care of the positioning 4 Set Frequency SF BACQ 9 25 MHz NUC 1H and tune the probe as described in the tutorial section Section 3 6 5 Now set the following parameters to the indicated values e RF attenuation 25 e AFGain 1 e EXP pp e Recycle delay 0 2 e TPOL 0 2 e Switching Time 0 003 e TAU 0 001 e BRLX e Block size 1000 e Sweep Width 500000 e FLTR 2770000 e Max Scans e Dummy Scan 0 e PW90 6to9 e RINH 16 NOTE All these default parameters are stored in a file std sample default par So the users can load using Load parameter in Tools menu these values from this file instead of typing them individually Please remember these values are to begin with the acquisition and not the Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 48 of 48 final parameters User should optimize all the necessary parameters depending on the signal condition 6 Press GO button to acquire one FID Now use F1 correction button to put the signal in resonance Now the User may play with the parameters like changing the gain
81. eport generated by the procedure has the same format as for the WAM procedure Likewise the graphic output of WSM also follows the same general rules which apply to WAM Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 92 of 92 4 4 3 7 Offset and Phase estimate This evaluation procedure is applicable only to quadrature detection data FTM 0 When applied to single detection data it issues a warning and does nothing more With quad data it generates two real values for each FID window 1 e one for each block The returned values are the estimated frequency offsets of the signal from resonance and its estimated phase just after the RF pulse time 0 The report generated by the procedure has the following format TAU Offset cor Phase cor 2 800e 01 1 259e 03 1 261e 01 2 615e 01 1 139e 03 9 465e 00 2 429e 01 1 134e 03 1 142e 01 where the offset correction is in Hz and phase correction is in degrees They are called corrections since they should be added to the acquisition parameters F1 and RPHS respectively to acquire an in resonance in phase signal Such an action of course is meaningful only with freshly acquired data and it is exactly what happens upon execution of the menu command Evaluate Correct F1 using last data in the case of single block experiments in multi block experiments the command first averages the offset amp phase corrections over the blocks specified by EW
82. er a couple of simple examples 1 Echo suppression under fast repetition conditions It is a common practice in C HR NMR to use repetition times comparable to the relaxation times in order to maximize the signal collected in a given period of time While using the standard SIP sequence this often leads to the formation of echo a small but perceptible increase of the FID envelope towards its end Such an echo is out of phase with respect to the main signal and since its relative magnitude varies from line to line it reduces the signal and complicates the phase correction of the resulting spectra Since the sign of an echo depends upon the relative phase of the two preceding pulses while the sign of the FID depends only on the phase of the last pulse the obvious cure is the following phase cycle 0 2 2 0 This is the commonly used single detection phase cycle in all commercial HR NMR instruments known as the AP mode It is also the phase cycle set up automatically by the AcqNMR software upon specifying the S1P sequence 2 Echo suppression in IR Consider now the Inversion Recovery sequence for the measurement of longitudinal relaxation curves The standard sequence is 180 tau 90 acquisition with the phases of both pulses equal This method is sensitive to the B1 inhomogeneity most often linked to the sample extending beyond the receiver coil There are two distinct complicating effects whenever B1 the RF field is inhomogeneous Fi
83. er to specify a data file either a new one or an old one Button Zap Discards the last acquired data zone of the data acquisition file It happens quite often especially when setting up the instrument that the last acquired data zone of the Data Acquisition File is of no more use and may be discarded This button provides a fast way to do so Button Kill Stops the data acquisition without completing scan and saving data 4 2 1 3 Scans Counter The scans counter panel is located in the upper part of the main window It displays the number of scans completed and block number in multi block experiments When dummy scans DS are performed they are displayed as negative integers The scans counter is updated about once a second When the actual scanning is faster this will cause the counter to apparently jump over blocks or even whole scans This is normal and does not imply any loss of data Remember that the data acquisition and accumulation is carried out by the AQM under stringent pulser control and timing The PC is simply periodically interrogating the AQM about the current status of the acquisition When the PC is real busy or holding on for some reason the scans display may even stop altogether but the scanning and data collecting nevertheless proceed normally As soon as the PC is free again the counter as well as data display gets updated 4 2 1 4 Top Macro panel The top macro panel is located in the upper part of the mai
84. erval parameter select it with the parameters cursor see accessible parameters and press O To edit all options use the View Parameter options menu and click the field of the desired parameter This in fact is the only way to edit the options when the parameter s value is inaccessible File parameters Parameters like FILE EDF1 EDF2 denote data files For such parameters the value field contains the clean file name without path while the path to the file s directory is written by the system into the parameter s options field This is only system supplied information the options field of these parameters is not directly editable 4 2 2 3 Editing of Parameters To edit an accessible parameter click its value field or press Enter while the parameter cursor is positioned at the parameter s name As a result a combo box appears over the parameter s value field and a new value may be entered The values listed in the pull down window of the combo box depend upon the type of parameter for parameters which have a limited set of allowed values a list in the pull down menu assists in the selection If the parameter is a string e g PHCY the input value must be one of the list otherwise the input is not accepted If the parameter is of a numeric type e g FLTR the admissible value closest to the one entered is selected for parameters which are not limited to a predefined set of values the pull down window shows the
85. es color to light blue this is the parameter cursor Each parameter page has its own parameter cursor which is lighted when the page has focus The cursor can be also moved up and down by means of the up and down arrow keys As it moves however it jump over parameters which are inaccessible or hidden When a User accessible parameter is marked by the cursor pressing the Enter key opens a value editing box in the parameter s value field the same effect is achieved by a single mouse click on the value field Some parameters in particular the RF pulses PW P1 P2 P3 and the delays D1 D2 D3 may be accessible not accessible depending upon the experiment or context The fact that a parameter is accessible and its value can be edited does not mean that the same applies to its options The two concepts in fact have nothing in common see pulser interval parameters Inaccessible parameters The values of some inaccessible parameters are displayed but cannot be edited Inaccessible parameters essentially just convey information The background color of the name and value fields of an inaccessible parameter is very light gray Clicking on any of these fields has no effects The inaccessibility of some parameters in particular PW P1 P2 P3 and delays D1 D2 D3 depends upon the experiment pulse sequence loaded In principle inaccessibility is context dependent It may happen that a parameter is inaccessible and
86. es the corresponding Nyquist frequency taking into account current value of FTM b sets the corresponding dwell time DW C considering the current value of block size BS calculates and sets the sweep time STIM d when autofilter parameter AFLT is set uses DW to calculate and set the proper filter FLTR Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 71 of 71 Such local chains of interdependencies some with loops are a rule rather than an exception and their complete map is of considerable complexity Fortunately they operate in a completely automatic way and in most cases in accordance with User s intuition 4 2 2 6 Pulser interval parameter options Every pulser interval parameter has apart from its value a User accessible field in which it is possible to specify a number of additional mostly hardware oriented properties called options In particular they make it possible to define control Transmitter RF phase Transmitter RF attenuation Generic pulser channels switch Accumulation directive s known as receiver phase In the case of Fast Field Cycling one of four preset magnetic field level In HR NMR the decoupler state States of any pulser controlled device X device states At run time the options are normally hidden from view by one of the graphic windows In order to gain access to them use the View Parameter options main menu command or the Show options c
87. esolution which implies the use of scales that are different from the physical ones all normalizations are always kept track of by both the acquisition program and the data evaluation program The intensities of the FIDs and spectra are therefore always referred to a standard condition This normalization includes the gains of all receiver stages e g AF and RF gains in FFC and other factors influencing signal intensity If all scans are equal the same signal intensity is observed in any number of accumulations on the same sample the differences will consist in the noise level which decreases as the square root of the number of completed scans In other cases the result will be the arithmetic average of all scans This approach is found extremely useful in practice Consider for example the following consequences It is allowed to direct absolute comparisons between spectra of the same sample acquired with different number of scans It is admissible to make absolute comparisons between spectra acquired with different gain factors Notice however that Stelar can only guarantee the linearity and calibration of our own AF amplifier 0 2 precision while other gain factors may be only indicative 2 7 3 Hardware aspects of acquisition Experimental data originate at the RF receiver on the spectrometer console From there they are routed to a 4 order Butterworth programmable AF receiver and filter in the STELAR Console Interface CI and
88. esponding red LED will blink If the negative arm of MOSFET or one of its two fuses is broken the corresponding yellow LED will glow continuously NOTE When a large field is switched ON and OFF with a high slew rate all LEDs will blink faintly because of driver saturation It is normal and can be used to check the LEDs If more than 3 positive arm MOSFETS are broken and high fields are required for long times the power switches off and MBF Mosfet Bank Failure interlock is raised If this condition occurs you cannot switch on the power To determine the broken MOSFETs proceed as follows Check that slew rate is not more than 5 MHz ms Choose standard PP experiment Set the acquisition field at 8 10 MHz H Set the polarization and relaxation fields at zero level Check that switching time is at least 3 ms Better set it to 5 ms Launch Go and Adjust mode Check MOSFET bank for blinking LEDs Switch off power Check gate and source fuses and MOSFET next to blinking LED Usually broken fuses mean that the corresponding MOSFET is broken 10 Replace broken parts 19 O0 rug UA cs acp Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 29 of 29 Always Cooling Mode There is an option to keep the cooling circuit in always cooling mode which efficiently reduces the thermal stress on magnet and the observed error in T measurements are lowered sufficiently when compared to cooling amp bypass mode U
89. essure indicator rear side of Magnet enclosure related to tap water pressure interlock Control switch If the pressure and or flow of primary coolant liquid water goes below the set point indicated by the red pointer in the case of pressure it enables the tap water pressure interlock and switches off the magnet Note Flow meter is not visible in the above picture To change the threshold in Flow meter the wooden panels have to be removed 2 7 Data Acquisition principles 2 7 1 Preparing for an acquisition Before starting an acquisition make sure that All the required hardware has been installed enabled and tuned probehead decoupler cooling air homogeneity VTC etc The sample is in place and if required spinning The desired acquisition parameters are specified We recommend a specify beforehand The non essential parameters such as the file name notes sample name temperature etc can be specified even at this stage Also make sure that the parameters are reasonable Despite all the internal checks it is possible to devise an experiment dangerous to the health of the spectrometer Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 32 of 32 2 7 2 Data Normalization In all Stelar systems the data intensities are always normalized to an absolute scale This means the following While the acquisition and display hardware is exploited to its maximum capacity and r
90. extension par of parameter files is automatically appended A parameters file is a plain text file containing a list of all parameters Each parameter entry contains its current value and if operational its current options Loading parameters from a parameters file or data file Loading parameters from a parameters file is quite straightforward and requires only the specification of the path name of an existing parameters file Not all the parameters are actually saved loaded in from the parameter files In general only the parameters which characterize the data are considered these are the same which are saved together with data in individual zones or data files Parameters which regard only the data Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 77 of 77 system environment file name current path current zone the console interface CI technical characteristics or other hardware configuration parameters are obviously not transferred Notice that upon exit AcqNMR program the system always saves its last parameters and re loads them if present upon executing again This last parameters file is called Last par You may reload it at any time if you wish to restore the start up conditions If you delete this file a set of primordial parameters will be created based upon the sacred parameter definitions file def please do not think about modifying these def files 4 2 3 Immediate Executio
91. f such RF ringing is easy to estimate since its characteristic time is QT where T is the period of the operating RF Thus for a probe of Q 50 tuned to 50 MHz we expect the ringing decay time to be of the order of 1 us This is already quite bad since we need the ringing to decay in amplitude from that of the RF pulse to well below the signal level a ratio of at least 6 orders of magnitude In our example almost 14 us are needed for the ringing to decay by such a factor This is the reason why probe RF ringing is often the dominant contribution to the so called dead time of the receiver system When the operating frequency is lower than in our example the situation becomes progressively worse At operating frequency of 2 5 MHz for example a Q factor of 50 leads to QT 20us with a detectable ringing duration superior to 280 ps long enough to simulate an NMR resonance line with a half width of 16 kHz The recognition of such an artifact can be made exploiting the following criteria 1 The probe RF ringing signal is independent of the presence of the sample 2 It is also independent of the applied static magnetic field this distinguishes it from acoustic ringing Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 44 of 44 3 Unlike a true NMR signal it cannot be inverted by applying a 270 degrees pulse While its dependence on the phase of the RF pulse is the same as for true NMR signals the dependence on i
92. fied and filtered Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 6 of 6 2 3 Switching ON and OFF the Relaxometer Switching ON Switch ON procedure is described below The different parts or switches can be located on the photographs shown at the end of this section Fig 3 by following the corresponding letters in square brackets with bold italic for example A 1 2 7 8 Open the primary cooling water supply tap Check the magnet cooling liquid level A Turn on the Main Switch This switch is located at the bottom of the rear panel of Magnet Power Supply and Cooling System Unit Switch the main AC power of the magnet power supply ON the knob is located on the left side of the Magnet Power Supply Unit front panel with a title Electronic Power Supply B This switch also gives power to the Cooling System Turn the AC power switch of the RF and digital unit C ON This switch is located on the right side at the bottom of front panel of the Spinmaster console Turn the cooling system ON by pressing the buttons in sequence RESET and PUMP ON on the left side of the Magnet Power Supply and Cooling System front panel D Keep the PUMP ON button pressed for 2 seconds At this point all the four interlock lights of the cooling system should be off and the pump should be running Switch the computer ON and execute the AcqNMR32 program Select Magnet ON in Hardware Menu to turn
93. field offset The current offset of the magnet is critical while measuring 7 at low magnetic fields 50kHz of H A positive offset may limit the minimum Larmor frequency to several kHz causing an artificial plateau in the 1 7 vs v curve a negative offset will produce large difference between nominal and effective fields It is better to perform this calibration when the apparatus has run experiments for several hours To correct the current offset IOFF select Calibrate Magnet offset in the Hardware menu The magnet current will be automatically calibrated The presence of the Earth s magnetic field and any residual magnetic field at the position of the magnet due to other sources e g other super con magnets may be partially compensated The parallel component relative to the Zeeman field of the magnet of this net residual field can be partially compensated using a magnetic field offset The value of this parameter is fixed in the Hard menu under Acq Par page FOFF For the best result user is requested to do this calibration manually as described at the end of this sub section Parallel component compensation becomes important only for relaxation fields lower than 10kHz or when the sample has a strong dispersion in the low kHz frequency range Default profiles using the macros stop at 10kHz and therefore only calibration of the magnet current offset is necessary If at 10kHz a non exponential magnetization evolution is
94. ge of the real pulser Once the actual value is known the system displays it in the parameter value field by appending the string lt value gt to the formula In our example if D1 is 0 3 the value field of D2 would eventually show 2 D1 0 6 The following rules apply to parameter value formulae 1 An expression must be enclosed in parenthesis to inform the program that a calculation should be needed The opening parenthesis is what tells the computer that there is a formula rather than a simple value 2 All four arithmetic operations may be used 3 Parentheses may be used as usual provided they are properly closed 4 There is no limit to the complexity of the formula 5 Arguments for arithmetic operations may be a numeric constants expressed in any numeric format b acronyms of parameters admitted in formulas see below The parameters admitted in formulas include All pulser interval parameters except the RF A selection of auxiliary parameters such as TIMX TPOL RD TAU and EDLY If the specified parameter is not allowed in the expression the program just issue a proper warning 4 2 2 5 Parameters interdependence Some parameters such as the User notes N1 N2 N3 are stand alones in the sense that they do not interact with others Most of the core NMR parameters however are inter dependent to a considerable degree Thus for example when a User changes SW the sweep width then the system a calculat
95. gt S BUS Signal IN F RF OUT OUT A INA OUT B L IN B Rx ON amp 1L Rx 1 S BUS amp L 3 S BUS 15v VDC LLL e PWR P10 Blank Out L 2 Tx IN Rx2 L i GATE P4 amp P5 to FFC Magnet S BUS power supply unit Host Comp B PT of Computer Tune o gt SYNT Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 20 of 20 2 5 Preparing for measurements There are several parameters to be adjusted and monitored before starting the experiment Users are strongly recommended to follow the procedures outlined in this section 2 5 1 Probe tuning Section 3 6 Probe tuning describes how to use the built in system to tune the probe perfectly The procedure requires 1 connecting the probe cables at the front end ii selecting the system frequency SF and executing the tuning routine iii adjusting the tuning and matching knobs of the probe until the monitor window of the PC displays a sharp resonance curve at its center Once the probe is tuned leave the tuning window by pressing Kill button and restore the RF connections for normal operation Then either hit Ctrl U or press the Update button in the Hardware menu to update the Spinmaster 2 5 2 Null current calibration and Magnetic
96. he acquisition delay parameter ACQD and the dwell time parameter DW Explicitly zi ajtib where a bx are the A channel in phase real and B channel out of phase imaginary components of the acquired signal Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 93 of 93 When projected onto the Cartesian complex plane an ideal FID describes a spiral with time as a parameter starting at a point zo at 0 and converging to z 0 with time going to infinity The mean offset from resonance is in this context defined as the mean rate of variation of the azimuth A z of z t This is a quantity which is easily estimated from the experimental data set note that since averages are involved the algorithm tends to suppress the unavoidable experimental noise The azimuth difference in radians between two data points z z is a b b a A z A z A z z sit a b Ya 4 b and the average offset in Hz for the given data set 1s 1 f zx xci A Z 4 Zy Once the offset has been determined it is easy to back extrapolate the azimuth of the first data point z to time 0 and thus determine the azimuth of zo which defines the overall phase or receiver phase of the signal This step however is burdened by the noise present in the single data point z no averaging and hence the phase estimate is much less reliable than the offset estimate and should be trusted only for signal
97. he details of AcqNMR software and its usage 4 1 Getting Started AcqNMR software comes with an on line manual AcqNMR hlp User can access this manual at any time by pressing the key F1 or select Content or Index in the Help menu Copyright Stelar s r 2001 Spinmaster FFC 2000 Reference manual page 61 of 61 4 1 1 Computer requirements The product is a 32 bit Windows program written for Windows 95 and Windows 98 operating systems running with an Intel microprocessor of the type Intel 80486 80586 Pentium IP or higher The code is compact and optimized and will run with any of these systems However the minimum recommended system requirements are A300 MHz Pentium II with 64 Mbytes of RAM Unless you are connected to a network printer make sure that you have at least two parallel printer ports e g LPTI and LPT2 One of these shall be used to interface the computer with the Stelar NMR hardware If you use a network printer and your LPT1 port is free you don t need any additional port Video resolution of 1024x768 pixels with large font and 256 or more colors The Stelar Spinmaster console connects just to a parallel port LPT1 LPT2 or LPT3 with no plug in board Windows 95 and Windows 98 are trademarks of Microsoft Corporation Intel 80486 80586 Pentium are trademarks of Intel Corporation 4 1 2 Installation Before installing the NMR32 software package please verify whether your computer meets the min
98. iles among themselves even though their instrument may have incompatible configurations from a Data file To load a complete set of system parameters from a previously saved data file zone use this submenu and select the option from a Data file When a Data source dialog appears select a zone of an existing data file default extension sdf and press the Open button to load the set of parameters it contains The criteria for parameters loading are the same as in the case of loading parameters from a parameters file For more information about the parameters used see the separate topic on Parameters List Pulse Sequence prints out the detailed list of pulser channel settings in current sequence This is rather technical information and may be of interest to you if you develop and test novel pulse sequence It is also helpful whenever you have any doubts about the details of the Stelar implementation of any of the pre programmed experiment Execution of a Macro command This command of the main menu permits to execute a macro The system prompts the operator for the input of a macro command name and proceeds further based on the commands written in that particular Macro Evaluate The Evaluate entry of the main menu contains the following commands Evaluate data On line data evaluation Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 64 of 64 Correct F1 using last data Used for fa
99. imum requirements Section 3 1 1 to run it You then decide in which directory you want to install the program if it does not exist yet create a new one and copy into it all the program files If the package you have received is zipped unzip it directly into the directory you have chosen If the directory where you have just copied the new version contained an earlier version of the NMR32 program it may contain the file Last par with values of last used parameters We recommend that before running the new version you delete this file in order to avoid possible parameter conflicts 4 1 3 List of program files The NM32 program package contains the following files AcqNmr exe Main executable AeqNmr hlp On line manual Aqm96 rom Acquisition and Control Manager loadable firmware Hardware def Hardware configuration definitions user specific Parameters def Default value for NMR parameters Nuclides def Table of nuclides and their basic properties DefaultSequences ssf Pulse sequence scripts supplied by Stelar DefaultMacros smf Macro commands scripts supplied by Stelar During execution the program may generate additional files of the following types par Parameter file sdf Stelar data file containing raw acquired data parameters sef Stelar export file Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 62 of 62 4 1 4 Copyright Agreement The NMR32 package is protected against
100. including a network Users are encouraged to write their own pulser sequences and store them in their own pulser sequence files Basic Rules There are some simple rules which hold everywhere within the body of a pulse sequence script Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 101 of 101 1 Extra white space is ignored Things like strings of blanks and or tabulators for example have the same meaning as a single blank A new line is recognized by the LF line feed character CR carriage return is treated as a blank and so are all other ASCII control characters 2 Apostrophe starts a comment extending up to the end of the line 3 Sequence header Pure comment lines immediately following the SEQUENCE declaration line constitute the sequence header which is displayed in the preview box in experiment sequence selection dialogs It may and should contain a brief description of the sequence and instructions for the final User on how to use it 4 Empty lines are ignored The only exception to this rule is header termination since an empty line is sufficient to terminate the macro header 5 The script is structured as a series of instructions or commands Longer commands are usually written one per line in which case they do not require a special terminator the line feed itself is a valid terminator Short commands however are often packed several per line in which case they must be ter
101. ing Power System Supply and H control Probe circuits for switching Temp Control Workstation RF Unit Data System Software Control LIII Sii NS Mis Acquisition Fig 1 Block diagram of FFC NMR relaxometer FFC Spinmaster consists of five different units each one containing several subsystems these units and subunits are listed below Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 3 of 3 1 Spinmaster console e Variable Temperature Control VTC unit for sample temperature control e Pulse programmer and signal acquisition AQM unit e RF unit DDS RF synthesizer RF Receiver RF Power transmitter e Power supply unit 2 Magnet Power Supply e Power MOSFET Banks Reference and Field Regulation units Interlocks system Current and Magnet temperature display Magnet temperature compensation system Electronic power supply for all the above mentioned systems 3 Cooling System e Magnet liquid cooling pump e Cooling liquid tank reservoir e Cooling liquids heat exchanger 4 Magnet and Probe e Magnet e Probe and air flux heater e Preamplifier and front end box 5 Computer and AcqNMR32 software for data acquisition Specifications of the Spinmaster FFC NMR Relaxometer Magnet Special design aluminium air coil system Maximum field 0 5 Tesla Homogeneity f better than 100 ppm over lcm Power Supply Max P
102. itive the block is considered in phase with the reference data and assigned a positive value otherwise it is considered to be negative Notice that since both real and imaginary components of the signals are used the procedure is totally insensitive to the receiver phase mis adjustment It shall fail and make incorrect sign estimates however when there are large signal phase variations between the blocks Though this is not likely to happen barring a hardware defect a situation of this kind may be simulated by instabilities of the signal offset due to magnetic field variations combined with the use of data points far from the RF pulse Just after a pulse the signal always starts with the correct phase regardless of its offset from resonance However when there are field instabilities like it might happen in FFC the good region may be masked by the system s dead time and or by the use of data window points with excessively large indices Any sign mis attribution is usually immediately evident from the generated multi block graph non monotonous curve If this happens follow the above generic guidelines to correct the problem or if possible avoid using the WSM routine In any case if the multi block graph is not monotonous don t use the RSM procedure to evaluate the relaxation rate of the data The data generated by this procedure are subject to the same rectification problem as in the case of the WAM procedure In some
103. ix and the fixed detection field Bacq The next trace shows the transmitter gate with the RF pulse of width PW90 followed after a small delay by the FID acquisition The last trace shows the times involved TPOL polarization delay SWT magnet switch off on time TAU variable relaxation interval For every given Brix the signal is measured as a function of the time TAU keeping the other times constant This time dependence is due exclusively to the relaxation in the field B Similar definitions apply to the NP non polarized sequence Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 2 of 2 This is the instruction manual of Spinmaster FFC 2000 It is divided into three sections Hardware Tutorial and Software 2 0 21 Hardware Overview Stelar s FFC relaxometer is designed to measure the field dependence of NMR spin lattice relaxation time T Nuclear Magnetic Relaxation Dispersion NMRD profiles from 10 kHz to a maximum operating magnetic field of 20 MHz in proton Larmor frequency units Highlights Minimum operating costs no use of cryogen Wide field range from 200 uT to 0 5 T Multi nuclear operation Efficient and accurate temperature control 7140 to 140 C with a 0 1 C resolution Research grade versatility Stelar Universal NMR Console Simplicity of use fully automated acquisition of 7 NMRD profiles Cooling Solenoid enclosure Magnet Em Magnet Cool
104. lamp control shall be O We have chosen this one since it is still free Keep in mind that channels T transmitter gate R receiver gates F internal CPU flag D internal digitizer strobe and S sweep start have pre assigned meanings and may not be used One cannot use the channels specified by the parameters TXEN transmitter enable and PINC phase increment and the channels used up by other devices in this case I and V which control the magnet also The last thing to check is the TTL channel polarity defined by the parameter PCPM pulser channel polarity mask If the letter in the PCPM value string corresponding in position to letter O in SSPC value string is H the channel is at high TTL voltage when active and at low TTL voltage when inactive positive logic otherwise when the PCPM letter is L the situation is inverted negative logic Since there are also moments when the pulser output is disabled we have to check that in such a state the O output is low and the lamp is OFF This is configured by means of a pull up pull down jumper on the AQM board again if you encounter difficulties consult Stelar At this point it is sufficient to reenter the AcqNMR32 program and the f device becomes operative For example should we desire in some sequence to have the magnet in the P state polarization field and the lamp in the Y state ON during the D3 interval we would give D3 the options string m P f Y 4 2 2 7 Parameters opti
105. lock 1 1 067e 04 4 902e 01 7 800e 01 3 167e 05 1 220e 02 1 112e 02 Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 89 of 89 Block 2 1 067e 04 1 386e 02 1 099e 02 3 167e 05 2 000e 02 9 197e 01 The imaginary components of each data point are listed only when the data are acquired using quadrature detection FTM 0 The terms Real and Imag refer simply to the detector channels A in phase and B out of phase and do not imply the employment of any phasing algorithm 4 4 3 3 List of Stored Parameters LSP This evaluation procedure is much like the LRD list of raw data except that the Report it generates does not contain data but rather a list of all the parameters stored in the selected data file zone The parameters are listed in the same order in which they appear in the parameter tables with a line of hyphens separating parameters belonging to different tables Like LRD when graphic output has been specified the LSD procedure produces the DisDat graph This amounts to a very efficient and comfortable data zone preview since one ends up with a simultaneous view of the DisDat graph and a scrollable list of all pertinent parameters 4 4 3 4 Data Window Averages WAV This evaluation procedure generates one complex datum for each FID window i e one for each block The returned value is the arithmetic average of all the data points which lay within the window
106. meter if present contains a dot indicating the end of the phase cycle and all the following PHx parameters are marked as na not applicable The parameters editing routine checks that this structure is always maintained without the User bothering about it particularly In this case the phase cycle is said to have a length n The complete phase cycle which is programmed on the pulser consists of n repetitions i 1 2 n of the basic experiment specified by the parameter EXP each repetition differing only by the transmitter phases and the accumulation mode according to the corresponding PHi and optionally also by the decoupler and or X device settings see the appropriate Chapter of the manual Note that what actually set the transmitter phase are simply the pulser channels specified by the parameter TXPH There is a slight extension of this concept for instruments equipped with the Stelar synthesizers but we will now gloss over this detail There is no reason why if need be all these pulser channels could not be used for a fast control of devices other than the controller of transmitter phases and or the decoupler control In this way the existing software can be used to control laser flashes two distinct decouplers field gradients etc However the NMR3 software foresees a more coherent way of controlling such X devices See the Chapter on Decoupler and X devices for more details Phase Cycle Interleaving In principle MS scans c
107. minated by semicolons Script Section The body of a pulser sequence script is divided into two sections the sequence proper section followed by a setup section The end of the sequence proper section and start of the setup section is marked by the keyword SETUP The general structure of a pulser sequence script is therefore SEQUENCE SequenceName sequence proper section HSETUP setup section END SEQUENCE The two sections are scanned by the software at different times and for different reasons When a new experiment is specified parameter EXP the syntax of the corresponding pulser sequence script is checked both section Should an error be detected the script is rejected and the EXP parameter is not allowed to change Otherwise the script is loaded into a RAM buffer and its setup section is scanned in order to initialize the values and or access flags and option strings of any specified parameters The initial values and option string of the initialized parameters need not remain intact forever If the parameter is User accessible or defined by means of a formula including other User accessible parameters its value may be changed at any time by the operator At the moment of pulser programming the actual current value of each parameter must be used Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 102 of 102 It is during pulser programming that the sequence proper section is scanned by the softwar
108. multi state X device Other examples might be one or more field gradient generators pulsed UV or laser lamps etc Every pulse sequence EXPeriment contains a certain number of distinct classes of intervals during which the X device might be in a different mode The software must enable the User to assign freely the X device modes to interval classes Every such combination then represents a sub variety of the basic EXPeriment The AcqNMR32 software provides ways to label the operating modes of an X device by the following letters O C B H 0 1 2 3 4 5 6 7 8 9 assign a distinct combination of logical pulser channels to each of these modes letters by means of the configuration parameter DCCH decoupler channels The auxiliary parameter DCEN decoupler enable is used to indicate which of the logical pulser channels requires the decoupler to be switched ON assign any combination of X device modes to the distinct interval classes by means of the User parameter DCS decoupling sequence Note that the length of the DCS string determines the number of the interval classes in the selected EXPeriment The above listed possibilities even though apparently quite sophisticated are still not versatile enough for certain NMR techniques The different combinations of letters composing the string parameter DSC can be compared to the different settings of the RF phase of the pulses in a multi Copyright Stelar s r l 2001 Spinmaste
109. n see the modulation of frequency in the FID In this case user is requested to follow the procedure given above for null current calibration and environmental field compensation yel The following figure shows the result after completing the procedure described above Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 22 of 22 2 5 3 Sample temperature setting An art line of the operating instructions for the Variable Temperature Controller V TC is given There are two different procedures to be followed to operate above and below room temperature Please follow the instructions given below for better operation of VTC Connections 1 Above room temperature e Insert the heater into the probe glass dewar and connect the cable to HEATER socket on the rear panel of VTC e Connect the dry air or nitrogen gas supply tube to the appropriate places inlet and outlet and set a correct flow level on the flow meter regulator 11 Below room temperature e Connect the evaporator cable to the EVAPORATOR socket on the left rear panel e Fill the evaporator dewar with liquid nitrogen e Immerse the evaporator rod slowly into the dewar and wait for a while till it reaches thermal equilibrium e Clamp the ring fasten around the dewar neck e Connect the transfer line from the evaporator to the probe as described in Section 2 4 1 Operation e Switch ON the instrument or reset the VTC either by pressi
110. n Mode In the immediate execution mode the user manually edits the system parameters and then uses the immediate mode buttons to acquire data Go button and save them Save button In this mode there is very little automation but the User has the possibility to modify literally every aspect of the experiment It is used in general for preparatory work on a new type of sample samples or for development of new experimental techniques While the system acquires data in the immediate mode actions which use the instrument s hardware another acquisition probe tuning digital scope magnet null current calibration diagnostics etc are forbidden It will also not allow the User to change any of the system parameters which might have an effect on the data while parameters which do not affect data may still be edited In order to proceed with any such action the User must make sure that the data acquisition has stopped and that there are no unsaved data on the AQM Acquisition and Control Manager board For the first part stopping acquisition he she must either wait until the preset maximum number of scans MS has been reached or press the Quit button and wait until the current scan is completed and acquisition stops or press the Kill button to interrupt the acquisition and discard the acquired data For the second part getting rid of acquired data he she must either press the Save button and save the data in a new zone of
111. n window at the side of the scans counter It is visible only while a macro command is in execution see macro command mode in which case it bears the name of the command on reddish background When a macro calls another one the text in the panel does not change that s why it is called top macro panel In the immediate execution mode the top macro panel is not visible 4 2 1 5 Multi page control The main multi page control is a virtual display device bearing several tabbed sheets pages among which the User can choose by clicking the desired tab The following sheets are present Main parameters sheet Acquisition parameters sheet Evaluation parameters sheet Reports sheet 4 2 1 6 Overlapped display screens These are rectangular areas screens in the right part of the main window Since they are overlapped only one screen can be seen at a time The User can select a screen either by clicking the proper item in the View submenu or by clicking the right mouse button on the currently Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 67 of 67 displayed screen an action which pops up a fast menu which partially duplicates and complements the View submenu of the main menu The following screens are available XY monitor screen DisDat window Multi Block window User graph System log Parameter option 4 2 1 7 Status bar The status bar is located at the bottom of the main
112. nce frequencies the BO flux though the receiver coil oscillates and generates a signal which has nothing in common with the NMR signal from the sample The best way of suppressing the ringing is of course to get rid of the probe vibrations Despite a considerable amount of research in this direction success in avoiding this acoustic ringing has been limited due to various inherent reasons It can be shown that the phenomenon grows inversely with the square of the ratio of BO to the operating frequency While it is usually negligible for protons it becomes often a nightmare for nuclei with low gyro magnetic ratios such as deuterium nitrogen rhodium etc We will now show how acoustic ringing may be suppressed by means of multi pulse sequences and a proper phase cycling Apart from suppressing acoustic ringing these methods serve also as a test in those cases where it is not clear whether a background artifact in the FID is an NMR signal or probe ringing In order to separate a genuine NMR signal from an artifact it is first of all necessary to find a situation in which the two phenomena exhibit different behaviors ideally opposite In the case of the receiver zero offset for example it is sufficient to invert the phase of the excitation RF pulse good signal changes sign bad signal does not Acoustic ringing is more pernicious since it also reflects the phase of the RF pulse In order to make it behave differently from an NMR signal on
113. nd or communication error first exit from the software and follow the instructions given below Switch off the PC not just restart and Spinmaster Check whether the communication cable LPT to Spinmaster cable is connected firmly Then first switch on PC Switch on the Spinmaster and load the AcqNMR program Switching OFF 1 Exit from the AcqNMR32 program This operation should turn OFF the magnet power supply If this does not happen switch it off manually by pressing the OFF button E on the left side of the front panel of Power Supply and Cooling System 2 Turn the temperature compensation off by pressing the green toggle button F 3 Switch the cooling system off by pressing the PUMP OFF button on the right side of its front panel D 4 Switch the RF transmitter off by pressing the STAND BY button G 5 Switch the AC power switch on the RF and Digital unit C off 6 Switch the temperature control unit H off 7 Switch the Magnet Power Supply unit off by turning OFF its main knob B 8 Close the primary cooling water supply tap and the dry air nitrogen supply Booting the Spinmaster Console The Data Acquisition Manager AQM in the Spinmaster Console controls CPU hardware interfaces and data acquisition When the console is switched ON its application program s must be loaded from the host PC a process called booting the unit has practically no software except a small communication routine Once the p
114. ndard PC parallel port which transmits logical commands called interface primitives Its own CPU Z180 decodes the instructions into a set of commands to be sent to the hardware interface at planned time intervals Furthermore this CPU reports the current status of the hardware and of the experiment to the PC program AcqNMR32 programs the hardware units through a proprietary bus stelar iir je sends the acquired data to the host At boot time the Z180 executes a configuration routine and establishes communication with the PC In practice the time critical portions of the instructions are executed by the pulser which is loaded by the Z180 The host may stop start the Z180 and the instruction flow that it controls but the AQM executes the configuration and sequence instructions independently Fig 11 Front view of AQM Unit IN A 4 Channel A input for data accumulation from RF receiver unit IN B 2 Channel B input for data accumulation from RF receiver unit The Stelar bus is a parallel bi directional 8 bit bus generated by an AQM Acquisition Manager which controls the various subunits of Spinmaster DDS RF receiver etc Copyright Stelar s r 2001 Spinmaster FFC 2000 Reference manual page 17 of 17 EXT CLK 3 External Clock 40MHz input from DDS unit DAC 4 Analog outputs digital to analog converter PI 12 5 Programmable 12 channel pulser output P1 to P12 LED 6 Voltage indicat
115. nels All X devices are defined in the Parameters def text file in a way which shall be described below Once the definitions are made the X device may appear in pulser interval parameters options and thus take part in data acquisition phase cycling Typical examples of X devices are assignments based on current Stelar conventions m fast field cycling magnet field multiplexer with the following states O Off no pulser channel R Relaxation field pulser channel I A Acquisition field pulser channel V P Polarization field pulser channels IV d RF decoupler with the following states O Off no pulser channel C CW irradiation pulser channel O B Broad band modulated irradiation pulser channels OM H Homodecoupling pulser channels OX We shall use the m device as an example of how the X devices are defined Essentially just one parameter SSPC appearing within the Parameters def file is involved if it is not displayed in your Configuration Parameters Table you can inspect its current settings by means of the macro command ShowNmrPar with argument SSPC Its value is a string usually HTRRIVOMXFDSZ which assigns a letter to every pulser output channel ask Stelar for the order in which the respective BNC connectors are mounted on the AQM back panel What interests us more however is the options string of the SSPC parameter Even though SSPC is not a pulser interval and even if di
116. ng the RESET button or by pressing the keys 1 2 3 simultaneously e The text VTC91 appears on display for few seconds unless one of the following keys is pressed ENT PRT immediately terminates the 5 seconds wait and goes to the temperature monitoring routine 0 1 2 executes Program 0 1 2 if implemented CAL PRG invokes the SPECIAL PROCEDURES menu RST followed by CAL PRG will ask whether to switch over to the TD MATE operating system see the TROUBLE SHOOTING section FOR MORE DETAILS PLEASE REFER TO VTC USER S MANUAL e Press 1 when the message VTC91 appears on the display to set the temperature Now the unit will prompt for entering the airflow level and set point Once the set point has been entered the heater evaporator starts working The set temperature can be increased decreased later by pressing CAL PRG button and setting the new desired value Please check the appropriate LED s heater or evaporator and Power are ON 2 5 4 Temperature compensation of Magnet When a heavy current passes through the magnet coils during the experiment the resulting heat causes a mechanical stress that shifts the magnetic field produced by a fixed current This effect becomes important for high current long time pulses The temperature Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 23 of 23 compensation is a circuit that senses the magnet temperature and adds a current related to the temperature increase
117. observed it indicates the presence of a high magnetic field at the position of the magnet from other source s In this case it is recommended to compensate the parallel component To compensate the background magnetic field the following procedure should be followed 1 Load a PP sequence Bpol 10MHz 2 Set BRLX to zero Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 21 of 21 3 Set the magnet current offset IOFF and background magnetic field offset FOFF to zero in hardware configuration page Hard under Acq par page 4 Calibrate the Magnet offset by clicking Calibrate magnet offset in Hardware menu 5 Seta 0 5 to 1 second polarizing pulse TPOL and a long 10 s delay tau TAU Execute Go and Adjust Check the voltage across the magnet with the help of a multi meter During the polarization period the voltage across the magnet will be of the order of few volts hence the polarization pulse can be easily recognized Later during the relaxation interval tau the voltage across the magnet should be zero If it is not so the magnet B offset FOFF parameter should be used to adjust it during the relaxation intervals 1 mV corresponds to 650 Hz So the voltage across the magnet should be adjusted very near to Zero The following figure shows result of a multi block PP sequence 16 blocks when either the magnet current offset or environmental field compensation or both are not set properly One ca
118. of the operation as much as possible in order to avoid coolant losses through evaporation The coolant has no known toxic effects so no special precautions are needed b Magnet temperature Magnet temperature is measured using a thermocouple which is in thermal contact with the inner coil of the magnet This reading drives the main safety device the Magnet Over Temperature MOT interlock of the magnet A periodic check of this lecture is highly recommended The test is simple and is based upon the supposition that if the thermocouple is not correctly stuck to the magnet layer it will be cooled by the liquid flux giving as a consequence an incorrect lecture To have a proper comparative situation the thermal jump of the magnet after a current pulse applied using any PP or NP sequence needs to be measured installation of the relaxometer and later at least once in six months This test should be performed before starting measurements after A typical curve obtained through a PP sequence at different magnetic field levels is displayed in Fig 13a It is worth observing that the temperature of the magnet tends to reach an equilibrium value after sometime on the application of current Of course the raising velocity and final value of the temperature will be higher the stronger the magnetic field This imposes a limit on the duty cycle of the system In other words even when the maximum field is 0 5T it is not advisable to leave the sys
119. offset high field The system has no way to check whether the F1 offset really is where it should be with respect to the spectrum An incorrect indication may result in folding or in the reversal of the spectrum It is important to note that on systems which actually have two detectors in quadrature the FTM O settings will result in the use of both of them Systems with only one digitizer will simulate the other by replacing the second channel data with zeros lt is still possible to take advantage of the FTM 0 mode provided that one uses a correct phase cycle pseudo quadrature See also the Quadrature Detection section of this manual for more details Bl B1 field in Gauss This value is determined from PW90 RINH Receiver inhibit After application of a PW90 pulse the receiver is disabled for a RINH time to avoid loading the audio filter RINH is of the order of the receiver probe dead time Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 83 of 83 ACQD Acquisition Delay Acquisition starts after this delay time from the acquisition Pulse 90 pulse RPHS Receiver Phase To maximize the in phase signal just after the FID QPHC Quadrature phase setting To adjust the orthogonality of the two signal channels Further details can be found from the Quadrature Detection section PHCY Phase Cycle Enable To enable or disable Phase cycling method Further details can be found from Phase Cycling
120. ofile macro and asks the user to feed other relevant parameters like output DATA file name sdf format profile result file name sef format which will have BRLX TI R1 Error in R1 error in R1 Zone DATA file name Starting amp end value of BRLX TPOL CD etc A brief instruction is given in the window whenever the macro asks the user to feed the value Please read the instruction carefully and feed the data First the Macro acquires one data set at the Starting BRLX value with two scans to find out the approximate TIMX and F1 values and asks the user to verify this data set If this value is as expected press OK button and then the macro will continue to collect data no more input is needed You can see the result in Reports page also in the Stelar Export File sef At the end of the data collection the profile macro switches off the magnet automatically To avoid switching off of the magnet in case the User desires it to be ON just make the StandBY statement second line from the bottom in the Macro file as a comment statement insert an in the first column of the line 3 4 90 degree pulse calibration Setting a correct 90 degree pulse is very important in relaxation time measurement experiments One should take extra care of this 90 degree pulse width First set up a PP or NP sequence using a short T sample Go to the Conf menu under Acq par page and check the value Copyright Stelar s r l 2001 Spinmaster FFC
121. ommand present in many of the popup menus alternatively press Alt O The reverse is achieved by the View Hide options main menu command or by the Hide options command of popup menus alternatively press Ctrl O Once displayed the options can be edited in a way similar to editing of parameter values just click on the current option value or if you don t like mouse press O and a combo box shall appear allowing you to input a new value The input string may encode any number of elementary options In order to be accepted however it must respect a precise syntax The syntax of parameter options supports what was once known as phase cycling In its present form this concept goes much further allowing acquisition cycles in which during consecutive sweeps or scans various hardware devices not just RF phase selectors run cyclically through pre defined sets of states Taking full advantage of this powerful and exciting feature is very easy and does not require any modification of the program s executable i Transmitter RF phase As far as the software is concerned the RF phase controller is an intrinsic pulser controlled device which may appear in pulser interval parameters options with the pre defined device identifier p As such it may take part in data acquisition phase cycling An argument of the p device option specification may be any real number between 360 and 360 Its value denotes the RF phase in degrees which on Stela
122. on A Add the same as S Subtract always The diode detection being rather uncommon it is henceforth assumed that the normal phase detection is being used so that the and signs have their conventional meaning The accumulation sign setting is usually referred to as the receiver phase even though as in the above example it need not require any phase control hardware However we will see that in quadrature detection a completely general receiver phase handling may employ a hardware device Similar to the case of the transmitter phase alternative notations for the receiver phase are also quite common The most commonly used symbols x and x correspond to our and respectively Multi pulse sequences In the sequences with more than one pulse per scan the phase cycle codes admissible values of parameters PH1 PH2 are of the type pp ps In other words there is one phase code digit for each pulse In an n pulse sequence the number of transmitter phase combinations is 5 including the pulse suppression setting 4 Considering also the receiver phase options soon this number becomes overwhelmingly large The actual phase cycle programming therefore has to be guided by NMR principles in order to reduce the cycle lengths to reasonable values and to achieve the desired effects So far only four distinct phase setting values p 0 1 2 3 or 4 have been considered In reality the system will accept up to 16 distinct phase set
123. on of experimental data rather than a WINDOWS window By convention data points numbering starts at 1 Setting EWEP to 0 default is equivalent to saying until the last FID data point When non zero logic commands that EWEP should be greater than EWIP Should this not be the case the evaluation procedure automatically swaps the two values Since the first few points of a FID are often contaminated by pulse leakage and or filter settling artifacts the default value for EWIP is 6 However the User may set it to any value greater than 0 When any of the two parameters is larger than the size of the FID data array the evaluation procedure replaces it automatically by the actual size b EWIB and EWEB Evaluation Window Initial Block and Evaluation Window End Block respectively define an interval of data blocks to consider in multi block experiments these two parameters are ignored when evaluating a single block data set By convention data blocks numbering starts at 1 Setting EWEB to 0 default is equivalent to saying until the last data block When non zero logic commands that EWEB should be greater Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 88 of 88 than EWIB Should this not be the case the evaluation procedure automatically swaps the two values The default value for EWIB is 1 When any of the two parameters is larger than the actual number of blocks the evaluation procedure replaces it automa
124. ons syntax Pulser interval parameter options are specified by means of a single string script containing any number of elementary options which may be but need not be separated by white space AII specified elementary options shall be in effect during the pulser interval specified by the parameter Each elementary option specification consists of Device identifier which is a small letter specifying either an intrinsic device or a User defined one A list of arguments enclosed in parentheses and separated by commas Each argument defines a state of the specified device For User defined X devices the states are represented by capital letters In the case of intrinsic devices numeric values and special codes may be meaningful see below The list of arguments corresponds to one complete cycle specific to the particular combination of pulser interval amp device cycle lengths for different devices may be different When there is just one argument the device shall be set to the specified state in all scans Multiple elementary options with the same device are not allowed and shall not be accepted Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 76 of 76 Likewise elementary options specifying an unknown device shall not be accepted Example of a valid options string Assume that the specified options of D3 are x L y A B z P Q R presuming that there are three X devices x y z which can be set to
125. or Vdd Vcc Vss COM 1 amp 2 7 Serial ports Host Comp 8 Parallel port connection to the Host Computer s parallel port LPT S Bus 9 Stelar Bus to interface and control all the units 2 4 3 Power Supply Unit This unit provides the regulated dc power supply to the RF and Digital unit of Spinmaster including the Transmitter Fig 12 Front view of Power Supply Unit Z AC mains switch 2 RF Transmitter power ON OFF switch and interlock RESET switch 3 dc voltage indicator 8 5 8 5 18 5 18 5 V the corresponding fuses are inside the power supply unit To replace the blown fuses open the front panel and locate the fuses just below the corresponding LED which doesn t glow as an indication of the blown fuse 4 RF Transmitter Interlocks 5 Fuses for AC mains Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 18 of 18 Wiring Diagram of Spinmaster for standard operation TB Synt TB RFout TB Tx TB Pwr Computer LPT TB Gate Fig 13 Wiring external diagram of SpinMaster TB Tuning Box P4 P5 and S Bus from AOM to FFC Power supply unit back panel Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 19 of 19 DDS RF Receiver AQM Transmitter Tuning Box Probe REF 0 REF 0 REF 90 __ REF 90 AQM CLK _ gt EX T CLK PINC e P8 Tx PULSE Tx Tx OUT SIN S BUS
126. ords coverage of the whole spectrum by a nonselective pulse is much better All this boils down to the fact that in order to obtain results comparable to single detection the required pulse amplitude is two times lower a factor of 4 in power 3 When both signal components are known it is possible to calculate the FID envelope independent of offset in a direct way rather than indirectly through the Hilbert transform This is particularly interesting in Low Resolution FFC FID shapes of solids Pseudo quadrature When User s instrument has only one signal channel some of the advantages of quadrature detection listed above can still be achieved Putting FTM 0 the system will behave as though there were two data channels with one of them always giving exact zero as the output See the sub section on Quadrature Detection Phase Cycling of the Phase Cycling section of this manual to see how using proper transmitter amp receiver phase cycling This situation can be exploited to obtain much the same data as with quadrature detection The process unfortunately requires twice the time as single detection so that for a given accumulation time there is no improvement deterioration in S N ratio but the other advantages of quad detection are fully present 2 7 5 Phase Cycling 2 7 5 1 Phase Cycling in NMR The concept of phase cycling is very important in NMR It was originally introduced for the suppression of several types of instrumental
127. oupler X device appears There are always exactly as many of these parameters sets and accessible to the User as the set phase cycle parameters PH1 PH2 The default setting for each DCXn mimics the DCS sequence with the question marks replaced by O off The User may input for each DCXn any valid combination of the X device mode letters The combination becomes valid during the execution of the phase cycle PHn This scheme while relatively simple guarantees maximum flexibility required by many of the modern NMR techniques and gives the User the possibility to fully exploit his her fantasy in designing new ones 2 7 5 7 Elimination of Instrumental Artifacts Consider the simplest possible sequence SIP The FID collected in each scan consists of three parts 1 The desired noiseless signal generated by the nuclei 2 The noise generated within the sample and the receiver 3 The transient response of the spectrometer to the RF pulse in the absence of a sample These artifacts include zero offset spurious frequencies pulse induced RF ringing acoustic ringing etc The most obvious application of phase cycling aims at the elimination of the artifacts listed above as part 3 While it is conceptually impossible to eliminate the noise part 2 by any means other than accumulation those instrumental artifacts which are coherent with the excitation can be eliminated in just two scans This includes the zero offset and some of
128. overy sequence with CPMG detection multiblock version of IRCPMG to acquire a FFC NMRD profile using PP S and NP S sequences to acquire a FFC NMRD profile using PPX S and NPX S sequences with BINLBEND BGRD predefined by User to acquire a routine FFC NMRD profile using echo acquisition PP1E S and NP1E S to acquire NMRD profile using PP and NP sequences with CPMG signal detection to acquire NMRD profile using IR sequence to acquire NMRD profile using IR sequence with CPMG signal detection to evaluate T1 with user defined EWIP EWEP EWIB and EWEB on an already collected data file Off line evaluation to inspect a NMR Parameter including hidden parameters Copyright Stelar s r l 2001
129. ower 15 kW Max Current 350 A Switchable levels 4 levels off Bpo Brelax Bacq each level is software controlled with 12 bit resolution Switching time lt 0 15 ms MHz Mains 400 VAC 22kW and 220 VAC 2 kW Cooling Unit Dual independent thermally coupled loops Secondary is a closed circuit using a cooling fluid at room temperature Primary circuit uses tap water with regulated consumption Water request 2000 I hr of water at 20 C 0 7bar at maximum power Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 4 of 4 Temperature controller Standard Gas flow system Range 140 to 140 C Precision and stability 0 1 C Gas Flow 1000 l hr at 1 3 atm dehumidified and filtered NMR console RF broad band unit from 2 5 80 MHz Two channel receiver with quadrature and envelope detection PC based data acquisition system Real temperature range at sample position strongly depends on dewar glass isolation 2 20 Installation The typical space needed by the Spinmaster FFC 2000 is about 16m as shown in the following figure Fig 2 364 cm E O Mains Q 400V 32A AC Water 7 A 60 cm E E g5 A S 80 cm O m t a c 2 s8 2 85 o Pil as 8 r8 224 cm N2 dewar for sample temperature controller 230V AC Air Printer Computer S and 5 controls S 3 Spinmaster 5 RF console o o N EAL T A SPINMASTER FFC2000 S R Suggested installation plan Fig 2 Typical inst
130. pinmaster a Universal NMR console Spinmaster consists of Variable Temperature Controller Unit A RF and Digital Unit B and Power Supply Unit C as shown in Fig 4 A brief description and functioning of each unit is given in the following sections The different parts or switches can be identified in the photograph by following the corresponding letters in square brackets with bold italic for example A Fig 4 Spinmaster Console A Variable Temperature Control Unit B RF and Digital Unit C Power Supply Unit Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 10 of 10 2 4 1 Variable Temperature Controller Unit optional Spinmaster Variable Temperature Controller allows setting of the sample temperature between 140 and 140 C with a resolution of 0 01 C and a small temperature gradient over the sample region The incorporated calibration procedures allow fine sensor and set point calibration in order to minimize temperature gradient on the sample The front and rear view of VTC Unit is shown in Fig 5 and Fig 6 respectively 1 2 3 4 5 Fig 5 Front view of VTC unit 7 Air flow meter to monitor and regulate the airflow 2 AC main switch switches ON OFF the VTC unit 3 Safety Interlocks gives basic diagnostic and troubleshooting 4 Display unit displays temperature 5 Key pad sets the temperature and allows keying in the program VTC Rear Panel
131. program window It is divided into two single line windows The left window displays short hints as the User moves the cursor over various controls and menu items The right window displays the X and Y coordinates of the mouse cursor when it moves across the XY monitor screen on which there are displayed data The values are in real world units e g X is in milliseconds when an FID is displayed In the case of multi block data the block number is also shown 4 2 2 System Parameters 4 2 2 1 Parameters review Parameters are used to configure the whole system set up the hardware define the sequence of events during data acquisition annotate the acquired data configure some of the data evaluation procedures display evaluation results etc etc In a certain sense every statement that can be made about the state of the system and or the acquired data amounts to specifying the value of some parameter The program manages over 200 parameters of which about one half are displayed Roughly half again of the latter can be edited by the User while the remaining ones are not accessible but display useful information The parameters together with their attributes flags default values and options are defined in the parameters definition file Parameters def This is an installation specific plain text file Extreme caution must be exercised while editing this file since certain modifications are potentially detrimental to the instrument hardwar
132. r FFC 2000 Reference manual page 38 of 38 pulse sequence It is therefore hardly surprising to find out that just like what has been done in the way of phase cycling is to be introduced as the concept of X device cycling In order to appreciate the need for the use of this concept consider the following classical example Suppose that the state of a device e g a broadband decoupler prior to an NMR scan is suspected to have an influence on the acquired data In order to verify this suspicion one might acquire two scans one with the device ON during the relaxation delay and one with the device OFF A comparison of the two data blocks would give us the answer in this case a rediscovery of the NOE effect If the nature of signals is such that many scans need to be accumulated then it would be best to alternate the two types of scans and add subtract them to from the data accumulation buffer The above of course is X device cycling at work Usually X device cycling is intimately combined with the RF pulse phase cycling The AcqNMR software combines the two cycling processes in the following way If the DCS sequence does not contain a question mark in any position then the sequence is repeated exactly as is done during each phase cycle In other words there is no X device cycling If the DCS sequence contains a question mark in one or more positions then a new Parameters Table containing the parameters DCX1 DCX2 DCX stands for Dec
133. r instruments the RF phase is digitally controlled with a resolution better than 1 degree Alternatively one can use the following symbols for standard RF phase settings X 0 degrees y 90 degrees x 180 degrees y 90 degrees Example of a valid phase cycle specification p x x 45 45 y y Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 72 of 72 Clearly the transmitter RF phase is irrelevant when there is no pulse Consequently it is usually specified only for the PW and P1 P2 parameters though it is not formally illegal to specify it in any pulser interval parameter Such a specification however has no practical effect since the RF phase is set to the receiver phase value parameter RPHS whenever the transmitter is gated OFF When the phase option is omitted the default value of 0 degrees is assumed Exploiting the p device option one can easily program the so called composite pulses with almost arbitrary in pulse phase variations i1 Transmitter RF attenuation As far as the software is concerned the RF attenuation controller is an intrinsic pulser controlled device which may appear in pulser interval parameters options with the pre defined device identifier a As such it may take part in data acquisition phase cycling The a device option arguments may be integers in the range from 63 to 63 do not use the sign The values indicate relative observed transmitter outp
134. r l 2001 Spinmaster FFC 2000 Reference manual page 85 of 85 FICL Maximum F shift absolute value This parameter is used by the F1 correction routine menu command Evaluate Correct F1 Its purpose is to prevent a wrong F1 correction which might occur with very noisy data The current value of F1 shall never change by more than the value of FICL For example if current value of F1 is 12000 Hz and FICL is set to 20000 the newly estimated F1 shall not exceed the interval of 8000 to 32000 Hz Should the calculated F1 value be lower than 8000 Hz it would be replaced by 8000 Hz likewise should it exceed 32000 Hz it would be reset to that value The default value of FICL is 50000 Hz The User can change this to anything from 10 kHz and 100 kHz clearly only positive values are allowed The limits are specified in the Parameters def file and if need be may be changed Note The F1CL value does not limit the User in directly setting the F1 value either manually or from a macro It is tested exclusively upon exit from the F1 correction routine TICR TI correction routine TICR is a parameter with a predefined list of possible values There are three types of relaxation rate estimation procedures that exists in this software This parameter is to select one out of the three procedures to be used for T1 correction method For a detailed description of the individual evaluation procedure see the following section Numeric Data E
135. ractical recommendations One does not need any particular speed while working manually setting up parameters checking on things etc It is only needed in long accumulations and or in automations So prepare your acquisition using the BASIC mode and if you need to go at maximum speed switch to the MUTE mode only before launching the automated acquisition If what you plan is an acquisition controlled by a macro and generating lots of data zones you can always write the macro in a way so as to display the data of the preceding zone while a new one is being acquired Alternatively if monitoring the input is what you want you can always hook up a classical scope to the analog inputs 5 Available pulse sequences and Marcos There are several pulse sequences available in the DefaultSequences ssf file When you select a particular pulse EXP from the default file a detailed description of that pulse 1s displayed on the window However here we list the pulse sequences available for the user Pulse Sequences ANGLE FFC nutation angle determination PP Simple pre polarized sequence PP S balanced multi block pre polarized sequence PPX S Balanced multiblock pre polarized sequence without TAU range defaults NP simple non polarized sequence NP S balanced multi block non polarized sequence Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual NPX S defaults PPIE PPIE S NPIE NPIE S IR IR S
136. rameter Considering that the AQM manages two input channels the in phase A channel and the out of phase B channel and two corresponding accumulation buffers I and II the four accumulation modes are Rec phase A buffer B buffer X added to I added to II x subtracted I subtracted from II y addedto I subtracted from I y subtracted from II added to I With this convention setting up both single and quadrature detection phase cycles is extremely easy since there is a direct correspondence between the RF pulse phases and the receiver phase In the one pulse sequence in particular when the pulse phase is cycled according to the PW parameter option p x x y y then the receiver phase must be cycled according to the corresponding ENDS option p x x y y in order to accumulate the data according to the quad detection CYCLOPS technique Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 74 of 74 v Magnetic field level in FFC A User defined X device is any external piece of hardware which can be controlled by means of one or more pulser output channels TTL control voltage levels Any such device can be assigned a device identifier a small letter other than p or a which are reserved for intrinsic devices Apart from the identifier one must also define a set of possible device states each of which is labeled by a single capital letter and is assigned a distinct combination of pulser control chan
137. rammed The chronological order in this section s items is essential since it defines the sequence of individual pulser steps during the pulse sequence execution Each sequence section command is 1 either the acronym of a pulser interval parameter 2 or a special pulser sequence directive preceded by the character ad 1 A parameter acronym defines a pulser step whose duration and active pulser channels are defined by the current value of the specified parameter and by its options Within this general framework however some parameters are associated with special default actions listed in the following Table Parameter Action RF pulses PW P1 P2 Turns ON the T channel transmitter D0 ACQD and STIM Turns ON the R channel receiver DO Sets pulser into ARMED state idle but with active output PW Resets the time origin automatic TIMEO directive STIM Triggers a sweep S channel ON for one step STIM Sets XOFF time scale offset of the sweep Note Each sequence should start with the pre scan delay DO which should not appear elsewhere The DO settings are also effective while the instrument is in the updated but idle state Sequence Directives The pulser sequence directives may appear only within the sequence section of a pulser sequence script They are distinguished from NMR parameters by being preceded by the sign and interpreted by the system during pulser programming and used to implement special actions such as
138. riodically for an update Executing an Automation Procedure The execution of an automation file is very simple Just select the Execute Macro in Tools menu or press Ctrl and M keys together and the system will guide you through the following steps a You will be asked to input few parameters not all acquisition parameters Since the automation routine presumes that all parameters not handled explicitly during its editing are completely free you might by error run a C13 automation routine with F19 probe and preamplifier Check for such obvious incongruencies and press Y or N If you press Y then b You will be prompted to input for the name of a data file Most automated procedures generate many spectra which are stored in separate zones of a data file By default the data file is supposed to be the currently specified one if any However the system will in any case ask for confirmation in order to avoid erroneous mix up of data Press ENTER to confirm the default file or type in a new name From this point on the execution of the automatic procedure will be fully operator independent except for actions which have been pre programmed into the procedure During any accumulation which is a part of an automation procedure you can interrupt the process by pressing Kill button In this case the system will ask for confirmation of the current accumulation abort and separately of the automation macro abort Please see the separa
139. rograms are loaded they accept acquisition parameters via the serial interface The process of setting the acquisition parameters of the AQM according to those displayed by the host acquisition program is called updating Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 8 of 8 Both booting and updating are done automatically when the console is switched ON the first time However it is possible to force a boot or an update at any time by selecting the corresponding buttons in Hardware menu or by pressing Ctrl B for boot amp update or Ctrl U for the update Note the boot always terminates with an update Magnet power supply Spinmaster Console and cooling system RF and Digital Unit Hn HE THOU o wu aS Fig 3 Photograph of Magnet Power supply and cooling system unit and Spinmaster console A Cooling Liquid Galden Tank B Power ON OFF switch for power supply and cooling unit C Power ON OFF switch for Spinmaster Console D Cooling system ON OFF Reset switch E Magnet ON OFF Reset switch F Thermal compensation circuit Enable disable switch G RF Transmitter ON OFF Reset switch H Variable Temperature Controller unit Power ON OFF switch I Magnet Current Voltage Temperature display switch J Opening for refilling Cooling liquid K Cooling Circuit main board Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 9 of 9 2 4 S
140. rs 3 Interface code size decadic or hex number This item is significant only if there is an interfaced parameter It specifies how many bytes of code does the interface actually use 4 The consecutive items are called Interface Configuration parameters They may be either decadic e g 13 or hex 0xD numbers which get loaded into a parameter s interface configuration array Their interpretation is device and type dependent and is normally explained on a comment line within the Hardware def file which follows the particular device definition script line As an example consider the device ObserveFilter whose definition script is gt ObserveFilter 3 SPM 31 100 470 30000 Sbus FLTR 1 5 2 The TypeScript 3 SPM 31 100 470 30000 indicates that it is of type 3 the contents of the following parentheses are irrelevant In this case the following type configuration parameters indicate that it has 31 steps per range and three linear ranges starting with cut off frequencies of 100 470 and 30000 Hz respectively The InterfaceScript Sbus FLTR 1 5 2 indicates that it is set by means of the Sbus device its associated parameter is FLTR the interface is done by setting a single byte which is to be written at the Sbus address 5 index 2 Should you analyze the Hardware def file you would see that the InterfaceScript of Sbus Aqm passes all interface requests to the Aqm device which passes them further to the Computer device which does the
141. rst the 180 degrees pulse is not perfect and generates a significant transverse component of magnetization which decays roughly within the same time as a normal FID say T Second the 90 degrees pulse is not perfect and this leads to the formation of an echo at time tau after the start of acquisition The amplitude of the echo decays roughly with T The corresponding deviations from the ideal behavior are Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 42 of 42 When tau is comparable to T the acquired signal is burdened by an undesirable component whichis a out of phase with respect to the signal phase distortion and b offset dependent When tau is comparable to T the acquired signal will comprise the echo depending upon the scan time Unless the echo is well distinct from the FID part of the signal it is impossible to eliminate it the result is an anomalous decrease of MO M for small values of tau especially if the evaluation is based upon peak intensities in the spectrum Both of the above problems are to a large extent cured by the phase cycle 00 10 02 12 the default for IR and IR S An alternative would be the implementation of a pulsed gradient unit and application of a homo spoil pulse between the two RF pulses 2 7 6 Ringing Artifacts There are three categories of false signals which have the property of changing phase in accordance with phase of the excitation RF pulse They
142. ry iii an rf modulator The clock generator sends a sinusoidal reference signal at 80MHz as output This clock output from the generator is divided by a factor of 2 and the resultant 40MHz clock output is available for Acquisition Manager The DDS controller is used to control the system frequency an NMR parameter can be varied from 2MHz to 90MHz and the phase difference between two channels real and imaginary RF and pulse modulator produce the pulsed rf output which is to be fed to the transmitter The level peak to peak of this pulsed RF output can be varied from 0 25V to 2 5V The quartz stabilized reference clock goes to the DDS to auxiliary outputs to the front panel and to a frequency divide unit which produces a 40 MHz digital clock for the AQM unit and a non committed 10 MHz digital clock for synchronization of an external synthesizer The DDS is a dual channel device which sends two sinusoidal signals in quadrature 0 and 90 with a frequency v lt 30 MHz limit set by the anti alianing filters as the outputs The main frequency selected by a logic input in the front panel is programmed through the DDS interface Both of DDS outputs are frequency multiplied and fed to splitters to provide the reference signals REF 0 and REF 90 to the receiver after a level tuning stage and to the transmitter modulator One output of the modulator switched by an external logic signal goes to a probe tuning output the other outp
143. s a systematic component which may be quite large and which is independent of the number of scans The apparent scatter however reflects only the reproducibility of the measurements which is the same as in the former case and tends to zero as the number of scans is increased Anomalously high fitting errors and normal dispersion curve scatter invariably indicate that the decays are not mono exponential and need to be handled by an external data evaluation software Keep also in mind that the reproducibility of the error estimate is much poorer than the error itself This is a normal statistical phenomenon an error estimate of let s say 2 may be easily burdened by an order of magnitude higher uncertainty so that repeated experiments may show fitting errors e scattered over an interval ranging from 1 to 3 4 4 3 10 Relaxation Rate Estimate Algorithm Let m and Ty be respectively the arrays of average data window magnitudes and of the arrayed parameter values the index k ranges over all considered blocks assumed to be n in number 7772 These data are to be fitted by the theoretical formula the hypothesis m T a be where a b and r are some as yet unknown parameters This requires a non linear three parameter least squares fit in which one minimizes the quantity Q a b r X m x a be with respect to a b and r It is convenient to split the task into two distinct parts Copyright Stelar s
144. s one step in the phase cycle The cycle starts with PH1 and terminates when a dot is encountered In the SIP experiment it is allowed to input codes of the type ps where p 0 1 2 3 4 and s Input 0 for PHI this refers to the first scan to be added to the accumulation buffer and 0 for PH2 this is the second scan with inverted RF phase to be subtracted from the buffer and a dot for PH3 in order to terminate the sequence during execution it will be repeated cyclically Now the phase cycle is ready set MS to an even number and GO 2 7 5 8 Compensation of Equipment Imperfections Even the signal actually generated by the nuclei is often not quite ideal This is due in part to unavoidable instrumental imperfections a perfectly homogeneous magnetic field an RF coil with perfectly uniform excitation profile an absolutely linear signal receiver a pair of absolutely identical LF filters for quadrature detection etc cannot be produced Signal distortions resulting from such imperfections are often minimized by proper combinations of transmitter pulse phases consider for example the Meiboom Gill modification of the classic Carr Purcell experiment Further progress can be often achieved by proper phase cycling We will consider a few typical examples Reduction of the receiver non linearity As a trivial example consider the case of receiver non linearity The transfer function of any receiver can be written as V A V
145. s with high signal to noise ratio acquired close to resonance In any case on most instruments the receiver phase remains constant in time and fairly independent of gain and filter settings Moreover it does not influence the outcome of T estimates so that its adjustment is in no way critical 4 4 3 9 Relaxation Rate Estimate RAM RSM RAV These evaluation procedures are applicable only to multi block data sets minimum 3 blocks in which the signal magnitudes depend exponentially on the arrayed parameter usually TAU When less than 3 blocks are present in the data zone a warning is issued and nothing gets done The difference between the procedures lies exclusively in the employed intermediate set of multi block data see the pertinent sections for a more detailed discussion of their nature These are RAM uses data generated by WAM data window absolute amplitudes RSM uses data generated by WSM data window signed amplitudes RAV uses data generated by WAV data window averages Internally the procedure first calculates the intermediate multi block data set and then calculates the relaxation rate R1 the inverse of T1 by fitting them to the formula m 1 a be and identifying R1 with the optimum value of r Here the index k ranges over all the blocks specified by the evaluation parameters EWIB and EWEB is the value of the arrayed Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page
146. se amplitude both relaxation and acquisition levels and send the data to us 7 Use the command Go and Adjust under Hardware menu to start scanning and then change the parameters as per the situation While you are in the Go and Adjust mode the system will allow you to change any parameter even during acquisition however the final data will be automatically discarded You should now see FID on the display window If there is no trace of a signal what might be wrong is the acquisition field intensity BACQ If the specified nucleus is proton H it must correspond to SF i e the RF working frequency 50 kHz otherwise it can be obtained by multiplying SF by the ratio Yu yx of the gyromagnetic factors of proton yu and of the specified nucleus yx If there is no signal even with the BACQ parameter correct check whether the RF transmitter is ON is easy to forget about it If it is OFF press Quit interrupt acquisition switch ON the transmitter and try again Otherwise there is a more serious problem Check the pre amp cable connections to make sure that there is no mistake normal connections are listed in section 3 6 You can also check if the magnet power supply unit is working as expected by connecting a scope to the SHUNT monitoring output on the Magnet Power Supply 8 Change the parameter F1 F7 observe offset Hz in steps of 5000 Hz until you get close to resonance you can make the step finer when you get clos
147. ser programming these values are converted to time intervals using the current 90 degrees pulse width PW90 as conversion factor Thus if PW90 is 5 usec and P1 is set to 180 degrees it eventually evaluates to 10 usec in Delay page DO to D16 Delay channel Depends on the sequence being used these delay channels are activated and assigned the values automatically according to the pulse script in nDim page NBLK Number of Blocks in an experiment The number of different TAU intervals is specified through the NBLK parameter number of blocks The default value of NBLK is 1 to save the time after setting all parameters specify the number of blocks otherwise the program will evaluate all TAU intervals at any change of parameters resulting in an unnecessary wastage of time BACR Block Acronym Parameter which changes between the blocks usually TAU BINI Initial value of the Block parameter For example in PP S sequence the initial value of BINI is 4 T1MX BEND Final value of the Block parameter default value is 0 001sec BGRD Block Grid type Type of point distribution from BINI to BEND Linear or Logarithmic or user specified Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 82 of 82 BLIST User specified point distribution from BINI to BEND For example if the user wants to use two different sets of point distribution over the range use the following rule Ay B T N3Ao B2 T N where A
148. sers are advised to use always cooling mode only if they have a closed loop cooling water system The only disadvantage of this always cooling mode when running water is used is the wastage of enormous quantity of water Follow the procedure to change this setting Open the front door of cooling pump unit Identify the dial A in the following figure on the left side of cooling liquid tank 3 Set the dial at the desired temperature and this will become the threshold temperature for cooling amp bypass mode pou Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 30 of 30 Galden Pump Pressure indicator related to cooling liquid pressure interlock If the pressure of secondary coolant liquid Galden goes lower than the threshold level indicated by the red pointer it enables the cooling liquid pressure interlock and switches off the magnet as well as the cooling pump Cooling Liquid pressure safety level set point swtich Galden Tank Pressure indicator related to cooling liquid pressure interlock If the pressure inside the Galden Tank becomes higher than the threshold level indicated by the red pointer it enables the cooling liquid pressure interlock and switches off the magnet as well as the cooling pump Pressure in Galden Tank safety level set point switch Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 31 of 31 Cooling Water pr
149. shes it from RF ringing Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 45 of 45 There are many methods to fight acoustic ringing of a probe assembly see for example the review by Gerothanassis I P Methods of Avoiding the Effects of Acoustic Ringing in Pulsed Fourier Transform NMR Spectroscopy in Progress in NMR Spectroscopy Editors Emsley J W Feeney J and Sutcliffe L H Vol 19 pp 267 329 1987 The best way is of course suppression of the probe vibrations themselves Despite a considerable amount of research in this direction there seems to be a limit to the reduction in acoustic ringing of the probe assembly An alternative way is the use of multi pulse sequences and a proper phase cycling as described in the frame Note on ringing artifacts 2 7 7 Arrayed parameter experiments A simple NMR experiment is based on what is often called a pulse sequence though much more than a sequence of RF pulses is involved one should talk about sequence of events rather than pulses In any case a simple sequence leads to almost a one dimensional data array consisting of a number of complex valued data points acquired at some pre defined time instants i e a Y t type of array which we shall refer to as an elementary data block A typical example is a single FID However the acquired data usually depend upon a number of parameters some of which may be pulser interval delays Thus for example classical rela
150. splayed its options string is not accessible the content of its options string is not a comment It is the place where all X devices are defined In the FFC case that we are discussing there the following specification m O R I A V P IV which is interpreted by the system as follows There is a device with identifier m which has four pulser controlled states labeled as O R A and P Each state is assigned a combination of pulser channels using the pulser channel definitions discussed in the preceding paragraph Thus for example when the delay interval D3 has been given the elementary option m P the m device shall be driven in state P during that interval meaning that pulser channels I and V shall be both active This is all we need to define and synchronize FFC magnet cycling with the pulse sequences Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 75 of 75 Let us now consider a hypothetical example Suppose we wish to interface a UV flash lamp controlled by a single ON OFF pulser channel synchronized with the pulse sequences with full data acquisition cycling capabilities We shall assign the letter f to this device notice that letters p a and m are already taken up and denote its states as O flash OFF and F flash ON We must edit the Parameters def file setting the parameter s SSPC options string to m O R I A V P IV f O F 0 In this case the pulser channel used for the
151. st convenience according to the signal characteristics Adjust receiver inhibit Rx inhibit us RINH and acquisition delay Acq delay us ACQD pulses in the Acq par page see the figure given below with the logic RECEIVER INHIBIT ACQUISITION DELAY In contrast with conventional NMR signal accumulation in FFC experiments does not guarantee an improvement on the signal to noise S N ratio due to the higher instability of the acquisition field However the problem can be handled by acquiring only a reduced window of the FID For this reason the default value of BS is 32 Anyway the system allows the user to apply his her own criteria Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 51 of 51 We start from the supposition that all the mentioned parameters are previously optimized using the NP or PP sequences Before loading the staggered sequence it is highly recommended that the user saves the parameters To do it the command Save parameters in the Actions menu should be used This operation will generate a par file in the working directory To select directory just specify it and the name of the data file in Acquired Data file FILE Now choose NP S sequence if BRLX is higher than 4MHz of proton Larmor frequency otherwise choose PP S sequence for T measurement Some parameters will be changed to defaults and must be defined again if you are using different values These parameters are BS Scan size
152. st offset correction Correct TIMX using last data Used for fast maximum T1 correction Hardware The Hardware entry of the main menu contains these commands and submenus Go and adjust Repeat the experiment while adjusting parameters Update Forced update of hardware interfaces Boot and Update Reinitialize AQM and update hardware interfaces Tune probe Probe tuning procedure Calibrate magnet offset Trims magnet current offset null value Simple scope Use the ADC s as simple scope inputs Magnet On To switch on the magnet Magnet Off To switch off the magnet Printer setup Standard windows printer setup protocol Diagnostics Run a diagnostics form Window Configuration The configuration entry of the main menu contains this submenu System log features To trace the hardware diagnostics activity Trace ON Write detailed output to the Log full trace of all activities Trace OFF Standard Log output only Edit system files To edit the default files such as def defaultmacro defaultsequences View The View entry of the main menu contains these commands XY monitor Brings to front the XY monitor graphic sheet DisDat window Brings to front the Display Data graphic sheet Multi block window Brings to front the multi block graphic sheet User graph Brings to front the user defined graphic sheet System log Brings to
153. sure T at the maximum desired frequency for the profile Save the parameters If necessary print parameters using Ctrl P or click Print parameters button in Tools menu Load the macro to be used and follow instructions Parameters such as maximum expected T pre scan delay polarization time etc would be required Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 53 of 53 Instructions to use the macro file DefaultMacros smf to acquire NMRD Profile automatically Load the AcqNMR32 program Load the basic PP pulse sequence Optimize all the relevant parameters for example BPOL Polarization Field BRLX Relaxation field PW90 90 degree Pulse width TATT Tx attenuation RINH Receiver Inhibit ACQD Acquisition Delay RPHS Receiver Phase SWT Switching Time BS Scan Size SW Sweep width FLTR observe filter RFA RF attenuation GAIN Af Gain PHCY Phase Cycle enable should be enabled for better result 4 Now try to get a very good signal at BRLX 1MHz Qua Once all the above parameters you are optimized User is ready to run the Macro Profile to acquire NMRD profile automatically Now Select Run Macro from Tools menu or by pressing Ctrl M keys together This window will show the defaultmacro smf file and ask the user to select the macro available in this defaultmacro smf file Now select PROFILE macro and press Accept button This action starts running the pr
154. t with different Polarization field BPOL 1 1 41 2 2 82 4 5 65 8 11 2 16 20 MHz For example 9e Lr 900 D Ur d DX E Field Tas Tnax AT Af Ave Af Jump MHz Hz Hz in Af 0 9 2 9 2 0 10635 10100 10461 10651 1 9 2 9 3 0 1 11926 11347 11527 1066 11308 1 41 9 3 9 5 0 2 10219 10763 10855 394 11583 2 9 2 9 6 0 4 9609 10479 10233 288 10611 2 82 9 4 10 1 0 7 9991 9916 10082 379 10340 4 9 5 10 6 1 1 9219 9121 9195 1266 9245 5 65 9 6 11 8 2 2 8413 8605 8500 1961 8482 8 9 6 14 1 4 5 6354 6413 6382 4079 6379 Copyright Stelar s r 2001 Spinmaster FFC 2000 Reference manual page 60 of 60 11 3 9 6 18 6 9 0 2334 2235 2259 8202 2208 16 0 9 6 28 2 18 6 8271 8602 8500 18961 8628 20 0 9 6 38 6 29 0 23671 23815 23783 34244 23865 Plot of AT vs Jump in Af gives the Mag Temp Compensation factor The slope of this plot is 1150 This is the correct value of Magnet Temperature Compensation Factor and should be inserted in the appropriate place Hard page under Acq Par page Slope MTCF 1150 0 5 10 15 20 25 30 Temperature AT in C 4 Software The purpose of AcqNMR software package is Data acquisition and accumulation time averaging Real time display of the data on XY monitor Storage and retrieval of the acquired data and parameters on a disk Display and evaluation of the acquired data The following sections will give all t
155. te document Macro Command Language Brief Review of the implemented syntax file name is MacroSyntax Doc for more information 3 7 Magnet Temperature Compensation Factor Before starting this experiment first User should locate and condition the proton NMR signal by adjusting the relevant NMR parameters For example the following values may be used EXP PP BPOL 10MHz BRLX 0 1MHz BACQ SF 9 25MHz TPOL 0 2 RD 0 2 MS 4 BS 512 SW 500000 Keep the FID at resonance using correct F1 function Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 59 of 59 Now the procedure described below should be followed to find out the correct Magnet Temperature Compensation Factor Hz deg C Switch off the Magnet Temperature Compensation button F Select PP sequence Set MS 1 TPOL 10sec RD 1 Set the magnetic field BPOL as 0 MHz Press GO button to acquire the signal Keep the FID at resonance and note down the F1 offset value Say FEY 0 Set BPOL as 1 MHz Note down the initial magnet temperature Click GO 0 During the 10sec Polarization period note down the maximum mag temp it could reach Due to this long polarization period the resonance frequency will shift and the FID will no longer be in Resonance Now select the F1 correction option and find out the correct resonance frequency Say FEY 1 12 Calculate the frequency shift difference between FEY 0 and FEY 1 13 Repeat the experimen
156. tem at continuous work The maximum field at which the system can operate with continuous current depends on the water temperature of the cooling system Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 26 of 26 e 4 MHz e 5 65 MHz e 8 MHz e 11 2 MHz e 16 MHz e 20 MHz AT in Magnet temperature C 0 5 10 15 20 25 By time sec Fig 13a Magnet current pulse vs thermal jump 2 6 3 Problems and Actions Smoke burning smell Press the emergency button at the front panel of the Magnet Power Supply and Cooling System and switch off the spin master console power supply as well as the VTC units Try to identify rectify the problem and or contact Stelar Magnet temperature If the magnet temperature is higher than usual after an hour or more of operation the likely cause may be the non functioning of primary water cooling circuit tap water pressure interlock would have been enabled at this point and it would have switched off the system automatically or a large current offset Therefore i Check the primary cooling water supply ii Check the presence of a high permanent current of the order of few A in the magnet by setting the display Z in Fig 3 in the current position Power supply If the power supply does not turn on even when all interlocks lights are off boot the Spinmaster console Ctrl B If the problem persists switch off th
157. temperature can be increased or decreased to the desired value later by pressing CAL PRG button and setting the new value Please check the appropriate LED s heater or evaporator and Power are ON 2 4 2 RF and Digital Unit The latest generation of direct digital synthesizers DDS programmable logic and fast A D amp D A converters are implemented in the RF electronics of Spinmaster The unit operates in the 2 2 to 80 MHz band and all pertinent settings system frequency transmitter phases attenuation signal phases quadrature calibration and probe tuning are under digital control The rf receiver is a dual channel quadrature detector with an option for amplitude detection A short receiver dead time lt 10us allows acquisition of NMRD profiles in solids with fast decaying FID s The pulser in the AQM unit has 12 digital output lines individually programmable with 50 ns resolution used to control the timing of complex RF pulses and external events Fig 7 RF and digital unit of Spinmaster Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 13 of 13 1 Direct Digital Synthesizer DDS rf Unit 2 RF power transmitter unit 3 RF receiver unit 4 Acquisition Manager AQM A summary of the functions of each unit with a wiring diagram is given below The schematics are provided with the system 2 4 2 1 DDS rf unit The DDS unit consists of 1 clock generator i1 a DDS with its control circuit
158. termines the dwell time DW i e the time interval between two consecutive samples of the data The relationship is SW 0 5 DW in single detection and SW 1 DW in quadrature Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 81 of 81 In both cases SW equals the Nyquist frequency The latter is the maximum frequency which when present is correctly defined by the digitized data any frequency which is higher will be folded back into the Nyquist range SW can therefore also be considered as the Spectral Window for the true signals Ideally however any signal frequency spectral line in HR FFC which is outside this window should be filtered out before the digitization Consequently a change in SW not only causes an update of DW but also sets a default value of FLTR the frequency cut off of the LF filters if you enable auto filter AFLT mode in Conf window RTIM Repetition time Not accessible to the user It is the repetition interval between the scans in seconds When T1MX TPOL are changed RTIM also changes accordingly TTIM Total time Not accessible Total time required for one experiment This value is calculated from the relation TTIM RTIM MS FLTR Cut off frequency of the audio signal filters in Pulse page PW Acquisition pulse default value is 90 P1 to P16 Pulser channel The values of RF pulses PW P1 to P16 are given in degrees of the nutation angle During virtual pul
159. the following states L for device x A B for device y P Q and R for device z The options specify that during D3 the three devices shall be in the following states x L y A z P in the first scan x L y B z Q in the second scan x L y A z R in the third scan x L y B z P in scan 4 x L y A z Q in scan 5 x L y B z R in scan 6 x L y A z P in scan 7 the same situation as in the first scan etc in a cycle of total length 6 In order to complete the example we need to know where and how are the devices x y z and their possible states defined For this we must distinguish between a pre defined intrinsic devices and b User defined devices which require a definition in the Parameters def file Please go through section 3 2 2 6 for more details 4 2 2 8 Saving Loading Parameters in from a Parameters File A parameter file is not to be confused with a data file since it contains only parameters and no data The default extension for this parameters file is par To save the current set of parameters in a parameters file use the submenu 7ools Save parameters When a file save dialog appears specify a file name or select an existing one and press the Save button When the specified file already exists you shall be asked whether it may be overwritten otherwise a new file is created Keep in mind that you don t need to specify the file name extension though you may do so When missing the default
160. the spurious Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 39 of 39 frequencies coherent spikes the RF ringing can be suppressed only partially due to its imperfect coherence Imagine for example that we acquire two scans the first one with the sample present and the second without a sample Subtracting the second from the first the coherent part of the artifacts i e that part which is reproducible in all the scans will be eliminated Similar results can be achieved simply by using zero pulse width in the second scan without taking the sample out however this will not compensate for any pulse induced transients Moreover since the second scan is void of any true signal it will degrade the signal to noise ratio S N A far better approach is to use in the second scan an excitation pulse of identical width as in the first one but with its RF phase shifted by 180 degrees phase inversion This leads to inversion of the true signal while leaving all the coherent artifacts unchanged Consequently the subtraction leads to their elimination while the signal is in fact added and there is no loss of S N ratio In a long acquisition one should therefore alternate RF transmitter pulses with phases of 0 and 180 degrees and in correspondence add subtract the acquired FID s Programming such a phase cycle is very simple Look up the parameters PH1 PH2 PH3 in the parameters table Each of them encode
161. ther arbitrarily When the number of actually completed scans is not a multiple of the phase cycle length the benefits of phase cycling are partially lost since the last cycle is incomplete This will make little difference in a long accumulation but should be avoided in experiments with moderate number of scans 2 7 5 4 Quadrature detection QD Phase cycling In this section it is assumed that the User already knows the principles and purpose of Quadrature Detection If not User is advised to read the corresponding section of this manual before proceeding further In QD the RF signal is split into two orthogonal LF receiver channels each with its own LF filters amplifiers and digitizers If the two channels do not have exactly the same gain or are not exactly orthogonal in phase the data will exhibit artifacts such as So called ghost signals in the spectrum which are reflections of real signals around the carrier frequency Modulations of the FID envelops in LR FFC applications Consider now the normal QD accumulation using the receiver phases and Let a denote the data vector acquired in one scan by the first digitizer and b the one acquired by the second digitizer Denote further I as the in phase component accumulation buffer and O as the out of phase accumulation buffer Then the accumulation with receiver phases or can be symbolically expressed as Receiver I I a O O b Receiver
162. therefore its value cannot be edited but this does not apply to its options In particular the options of all pulser interval parameters which are not hidden can be always edited Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 69 of 69 Hidden parameters A hidden parameter has a display location but is not used at all in the current context experiment pulse sequence Only its acronym is shown but none of its other attributes The background color of its field is dark gray and no field is accessible for editing Pulser interval parameters A pulser interval parameter defines the duration of an interval during the execution of an experiment pulse sequence It therefore represents an input datum for pulser programming Pulser interval parameters therefore include all RF Pulses PW P1 to P16 all Delays DO to D16 Receiver Inhibit interval RINH Acquisition delay ACQD Sweep time STIM End of sweep accumulation directives ENDS This is a pseudo interval of zero duration whose options define what is known as the receiver phase cycle The pulser interval parameters can also be easily recognized by the fact that when not hidden their options field has a white background color and can be edited The options of such parameters in fact determine which pulser channels are active as well as what is the observed channel RF phase and transmitter attenuation To edit a pulser int
163. tically by the latter value Note The right window displays the X and Y coordinates of the mouse cursor when it moves across the XY monitor screen on which data are displayed The values are in real world units e g X is in milliseconds when an FID is displayed In the case of multi block data the block number and point number is also shown Y EWIP EWEP Fig 15 FID obtained from a typical multi block sequence 4 4 3 2 List of Raw Data LRD This evaluation procedure does nothing at all with the data except converting them to an ASCII form It is used principally to export the raw data into ASCII files usable by other applications This procedure generates a report consisting of a listing of all data points comprised in the selected data zone Since the report may be quite long thousands of lines it may get truncated when sent to the program s Report Sheet 1000 lines maximum However no such truncation occurs when the report is written into an export file The following report format is used B
164. timum value Q of Q is due entirely to random experimental errors this is false for non exponential decays the least significant increment Ag Q can be determined for any given significance level by means of the Fisher statistic with both degrees of freedom set to n 1 The confidence interval Agr for r then comprises the r values for which Qi r Q Ag Q and the probable error e Ar 2 is obtained as usual by setting 00 69 This may sound complicated but it actually turns out that in the quadratic case the result is excellently approximated by the simple formula e Q2 n 1 Q1 r2 where Q r is the second derivative of Qi r which is easily estimated numerically Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 96 of 96 Appendix A 1 Parameter Definition file parameter def The Parameters def file defines the structure of the parameters set pertinent to your installation It is a crucial element of the NMR32 package which must be present in the same directory as the executable AcqNMR exe file When absent the program shall issue a warning and terminate before completing its initialization The file is installation specific Though most of the parameters are common to all Stelar instruments and MUST be present some of their values and properties may be specific for the particular instrument in question Moreover there are some optional parameters whose very presence are installation spe
165. tings which are countersigned by the characters p 0 1 2 9 A B C D E and F The exact setting of the pulser channels corresponding to these characters is given by acquisition parameter TXPH in the Configuration Parameters Table On those instruments which are capable of generating only four distinct transmitter phases the settings 4 9 and A F are normally configured as no pulse Instruments mounting the Stelar broadband synthesizer are capable of generating virtually any transmitter phase the standard transmitter phase values are then set to 0 0 deg 5 45 deg A 60 deg F 30 deg 1 90 deg 6 135 deg B 150deg G 120 deg 2 180deg 7 135deg C 120deg H 150 deg 3 90 deg 8 45deg D 30deg I 60 deg 4 nopulse 9 spare 0 E spare 0 J spare 0 Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 35 of 35 Review of the phase cycling concept The parameters PH1 PH2 are used to control the transmitter phase during each of the distinct intervals which appear in a pulse sequence as well as the associated receiver phase The latter is in quotation marks since for most instruments receiver phase is not under hardware control and the term describes the software mode used to combine the data acquired in a particular scan with the data accumulation buffer s The parameter PH1 must always be defined The subsequent PH2 PH3 are defined up to a certain number PHn The consecutive phase control para
166. tion In quadrature detection one uses two RF receivers whose reference frequencies are the same but for a 90 degrees shift in phase Stelar actually mounts two distinct digitizers and data accumulation buffers also so that the LF data from the two channels can be digitally sampled at the same time some other Companies use a single digitizer and multiplex the two channels In any case each channel s LF data pass through a distinct set of LF filters In order to use this Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 33 of 33 hardware just set the parameter FTM Fourier Transform Mode to 0 and adjust your carrier offset and or magnetic field to match the approximate center of the sample spectrum When both the in phase real and the out of phase imaginary components of the signal are available it is possible to place the carrier frequency at the center of the spectrum and use the complex FFT routine to distinguish between the positive and the negative frequencies The advantages of this arrangement are 1 Cut off frequencies of the LF filters i e the receiver band width may be reduced to half the value used in single detection This decreases the noise and therefore increases the Signal to Noise ratio by 41 square root of 2 For samples requiring long accumulations this slashes the acquisition time to one half 2 The full spectral power distribution of the RF pulse is exploited In other w
167. to a low value at the end of the polarizing pulse of a PP sequence The frequency F1 and current IOFF offsets should be corrected after setting the temperature compensation 2 5 5 Field homogeneity adjustment This adjustment is very important to get a better S N and also to minimize the error in 7 measurements Set the frequency a little off resonance F1 observed offset to get a FID with 5 20 oscillations Make sure that the sample 2mM MnCD2 solution is appropriate is kept exactly in the middle of the rf coil and adjust the probe position up and down to get the longest and most regularly decaying FID Fasten the probe at the optimal position Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual 2 6 Troubleshooting page 24 of 24 In this section we list security features possible problems and related solutions 2 6 1 Safety interlocks Spinmaster FFC 2000 is equipped with a number of safety interlocks designed to prevent major damages when a fault condition occurs The interlock circuits drive status LEDs which turn on when the interlock is active When any one or more of the interlock LEDs lights up try to reset it by pressing the closest RESET button If it persists to be lighted proceed as indicated below e Spinmaster Console LEDs located at the front side bottom right Transmitter interlocks Imax and Tmax Interlock LED Meaning Recommended Action Note Imax Excess curr
168. ts width is not with increasing RF pulse duration the probe ringing signal increases monotonously towards some saturation value while a true NMR signal follows the sine like nutation curve This is important since it is the only way to distinguish probe RF ringing from an NMR signal originating from the probe assembly materials There are at least three methods of fighting probe RF ringing Decreasing the Q value We have seen that the RF ringing transients decrease exponentially with decreasing Q while probe sensitivity decreases only linearly A modest reduction of Q may therefore be a good solution in situations where the problem is not too severe Active suppression It is possible to design fast gated switches which short circuit the probe for a few microseconds after the pulse and thus discharge the RF energy stored in its resonant LC tank Though such devices increase design complexity and represent an avenue for additional pick up noise they may be the only viable solution in the case of really severe ringing problems Special phase cycling sequences For a detailed description of this surprisingly efficient approach consult the frame Note on ringing artifacts Acoustic ringing of the Probe Acoustic ringing is a pernicious phenomenon which can sometimes impair or even preclude successful NMR measurements Its source is the mechanical vibration of the probe assembly after an RF pulse the effect often leads to audi
169. tting a full compensation of Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 37 of 37 both amplitude and phase mis adjustments of the two channels is known as CYCLOPS It has length of 8 and requires a hardware commutation between the two LF signal channels This hardware is not present in many older as well as some newer instruments 2 7 5 5 Table of implemented Receiver phases RXTAB Character Meaning orA Add U to AU Add V to AV ors Subtract U from AU Subtract V from AV Add V to AU Subtract U from AV Subtract V from AU Add U to AV Notes 1 In Diode Detection parameter PDMX D acts as Use of A S is suggested for really adding subtracting data 2 If the parameter FTM Fourier Transform Mode is set to 1 1 single detection and are interpreted as A and S respectively 3 If FTM is set to 0 quadrature detection and user s instrument consists of only one digitizer the software will work as though two digitizers were available but the data coming from channel V were zero pseudo quadrature 2 7 5 6 Decoupler AND OR X device Cycling Decoupler i e a second RF source is a device which has found ample use in NMR Usually it may operate in a number of modes such as C continuous wave B broadband modulated H homodecoupling mode or O off some of which can be further combined with different RF phase settings 0 1 2 3 As such it is an example of what is called a
170. ue of TIMX could be an important source of systematic errors It is highly recommended to run a test measure to set the proper value of this parameter before measurements The number of different TAU intervals is specified through the NBLK parameter number of blocks The default value of this parameter is 1 just to win time after setting all parameters specify the number of blocks otherwise the program will evaluate all TAU intervals at any change of parameters resulting in an unnecessary wastage of time Collect one FID and correct the frequency offset Correct FI in Evaluate menu After incorporating this correction correct the Receiver phase RPHS value as suggested by the program Now the setup is ready to start T experiment at a desired field Change the value of Max Scans MS to 4 Dummy scans DS to 0 or 1 or 2 and press GO button for data acquisition Dummy scans are useful to pre establish the thermal cycle of the magnet before Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 52 of 52 starting acquisition They are very important while using short re cycle delays Recycle delay s and a high number of scans After completing four scans save the data by pressing SAVE button and calculate the T value by clicking Evaluate dialog button in Evaluate menu In this page user can select various types of data evaluation like Ri estimate window averages magnitude offset and phase estimate Also th
171. unauthorized use by a hardware key This takes away from you the responsibility of making sure that no third party copies the package illicitly for his her own use It also gives you a complete freedom in making backup copies of the installation diskette we recommend the use running the software at your home as long as you care the key with you etc Any attempt at invalidating the protection key either in hardware or in software will be considered a deliberate violation of copyright laws Apart from any other legal actions STELAR will consider void any warranty and or maintenance contracts or agreements and stop any kind of service and or collaboration with a customer who will hurt our interests by transgressing this copyright agreement 4 2 Software Review 4 2 1 Main Window The main program window contains the following components Main menu Immediate mode buttons Scans counter Top macro panel Multi page control Main parameters sheet Acquisition parameters sheet Evaluation parameters sheet Reports sheet Overlapped display screens XY monitor screen Data Display DisDat Screen Multi Block graph User graph System log Parameter option Status bar 4 2 1 1 Main Menu The main menu contains a number of items each of which opens a pull down window with a submenu To select a main menu item either click on it or press the Alt key together with the letter underlined which identifies the menu
172. ut after a variable gain amplifier output from 6 to 14 dBm goes to the transmitter amplifier Fig 8 Front view of DDS unit Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 14 of 14 The output input of DDS Unit are Z The master clock output 80M HZ is available at two outputs 80 MHz SMB connectors 2 40M CLK gives 40MHz clock output which is to be connected to the AQM unit 3 An additional 10MHz clock output is available in the DDS RF unit 10 MHz 4 5 0 and 90 phase shifted rf outputs are available at the REF 0 and REF 90 OUT connectors 6 TUNE continuous rf output 0 dBm for tuning the probe 7 TX PULSE a transmitter pulse input from AQM Unit 8 TX OUT pulsed rf output to the RF power transmitter 9 P INC allows synchronization of Tx pulse phase with pulse sequence timing 10 F SEL allows a fast switching between two different Spectrometer Frequencies The levels of REF 0 REF 90 can be individually adjusted 7 dBm to 15 dBm with the two trimpots 77 near these outputs The level of pulsed rf output can also be adjusted Program 0 dB for Tx base attenuation parameter TATT and adjust the trimpot 72 to get the maximum pulsed rf level 2 4 2 2 RF transmitter Unit The 7f power transmitter unit of Spinmaster delivers up to 300 W in the pulse mode The maximum power level can be adjusted through the AcqNMR software TATT 7x base attenuation under Hard
173. ut attenuation in dB Example of a valid RF attenuation specification for P1 attenuated always by 6 dB a 6 Example of another attenuation specification for P1 pulse is alternately On and Off a 0 63 Clearly the transmitter attenuation is irrelevant when there is no pulse Consequently it is usually specified only for the PW and P1 P2 parameters though it is not formally illegal to specify it in any pulser interval parameter Such a specification however has no practical effect since the attenuator is set to 63 dB maximum suppression whenever the transmitter is gated OFF This helps the transmitter gate to suppress both RF and noise at any time except during a pulse The actual attenuator value set in the hardware is the sum of the a option specification and the value of the parameter TATT base transmitter attenuation which thus represents a pre defined null level The resulting sum must be within the range 0 63 dB When negative it is automatically reset to 0 when greater than 63 it is automatically set to 63 For example when TATT 15 then a 3 evaluates to 12 but a 18 evaluates to 0 and likewise a 3 evaluates to 18 but a 63 evaluates to 63 Exploiting the a device option one can easily program the so called profiled pulses with almost arbitrary amplitude envelopes Warning Although the attenuations are specified in dB the actual output level need not be what you expect since the specification applies to th
174. valuation Procedure T1CL TIMX correction lower limit T1CU TIMX correction upper limit These three parameters TICR TICL T1CU are used exclusively by the TIMX correction routine menu command Evaluate Correct TI MX Their purpose is a to specify which T1 evaluation procedure should be used and b to prevent a non sensual T1 correction which might occur when for whatever reason the data are pathological Note that in FFC Fast Field Cycling TIMX is a critical parameter since it determines the duration of the intervals when the magnet is switched ON Imposing an upper limit on TIMX is therefore not just a logical thing to do but an important safety feature as well TICL is the lower limit for TIMX Should the TIMX correction end up with a value smaller than T1CL it would be reset to this limit The default for this parameter is 0 001s 1ms with an allowed range of 0 0001s 0 1ms to 1s T1CU is the upper limit for TIMX Should the TIMX correction end up with a value greater than T1CU it would be reset to this limit The default for this parameter is 5s with an allowed range of 1s to 10s Note The TICL and T1CU values do not limit the User in directly setting the TIMX value either manually or from a macro They are tested exclusively upon exit from the T1 correction routine The default values of all the above parameters as well as their ranges are defined in the Parameters def file and should it be necessary can be mo
175. ware especially of game programs test them first Running programs which do such fine things as canceling the Host memory or Disk Beware also of resident programs they might be in conflict with AcqNMR Try them first extensively and if you have a problem contact us Button Quit Waits until current scan is completed and then stops acquisition The acquisition normally stops once the pre set maximum number of scans MS has been reached In some cases however the user may want to interrupt the acquisition manually This is particularly true in fact unavoidable when MS has been set to large value The manual termination can be achieved by pressing Quit button The system interrupts acquisition immediately upon reception of the Quit command If there is a scan in progress at the moment it waits until the current scan is completed and then stops acquisition Remember that in multi block experiments a scan consists of one FID in each block Button Cont Reserved for a future implementation of the continuation Copyright Stelar s r l 2001 Spinmaster FFC 2000 Reference manual page 66 of 66 Button Save Saves the acquired data to disk This command initializes the transfer of acquired data from the Console Interface into a disk file on the Host computer It appends the newly acquired data as a new data zone of the current Data Acquisition File data FILE If FILE value is void displays a file selection dialog and allows the us
176. we were loosing about 120 ms 1Kpoints always The new algorithm is much more efficient B Since the full BASIC mode processing cycle takes about 160 ms Kpoints things start changing when the theoretical repetition rate is smaller than this number In this case the processing cannot be completed in parallel and ends up delaying consecutive scan starts The most unfavorable situation is reached when the theoretical repetition time is lower than 18ms Kpoints The processing then does not allow it to go below about 160ms Kpoints slower than the old AQM In case A the parameter DAAP has no perceivable effect on overall acquisition timing Somewhat surprisingly however its effect is relatively modest even in case B The reason is of the 160 ms of processing roughly 20 are taken up by the flash buffer transfer 50 by data accumulation 50 by refreshing a scope image on the AQM and 50 by the actual transfer of the image data to the PC all values except the last one are intended for 1 K of complex data points Since the transfer to PC is asynchronous and has low priority not all blocks are transferred so that last number must be proportionally reduced The maximum average overhead then lies between about 150 and 170 ms Kpoints and its variation with DAAP is relatively small In FFC one normally uses small block sizes For example with a block size of 64 points the minimum overhead is about 18 64 1024 1 125 ms block while the maximum
177. xation time measurements employ two RF pulses separated by a delay tau and the focal point of interest is the dependence of the signal on the tau value In such cases one needs to acquire FIDs taken with many different values of tau which implies a series of simple sequences repeated until sufficiently detailed 2D grid of data points Y t tau is collected In principle one could collect the single FIDs manually changing the value of the parameter tau everytime This however would be extremely tedious To automate such procedures is the purpose of arrayed parameter experiments or as we shall call them multi block experiments Theoretically the arrayed parameter might be any of the system parameters which has any kind of impact on the data e g the filter cutoff frequency However the present software allows only pulse interval parameters to be arrayed Converting any simple pulse sequence into a multi block experiment is extremely simple All one has to do is to set a few parameter in the Acq Par nDim parameters table 1 Set the parameter NBLK Number of Blocks to some non zero positive value This shall enable the parameters BACR and BGRD Block grid type Depending upon the current contents of BGRD either the parameters BINI First value and BEND Final value or the parameter BLST List of ranges shall also become accessible 2 Within BACR Block acronym specify the acronym of the arrayed parameter e g TAU Keep in min
178. xperiment sequence The purpose of this parameter is to define what we call accumulation directives Accumulation directives tell the acquisition amp accumulation manager board AQM what to do after every pulser scan sweep A list of such directives is transferred to the AQM every time the pulser is programmed so it can be viewed as an extension of the pulser program At present the ENDS parameter s options follow the general syntax of all pulser interval parameter but only the phase option is significant and has any practical effect on the data It tells the AQM in which way the acquired data should be summed subtracted to the accumulation buffer after every scan a piece of information which is an essential part of any phase cycling process This information is traditionally referred to as the receiver phase a term originated from early days of NMR when data accumulation was carried out by rather inflexible hard wired gear and the flexibility required by phase cycling was achieved by using a special receiver phase selector acting on the two reference channels of the RF phase detector Today this kind of approach has been all but abandoned since it requires additional hardware where software is sufficient along with being much more flexible There are four different modes of adding newly acquired data to the accumulation buffers These are distinguished by the receiver phase settings x x y and y in the p option of the ENDS pa

Spinmaster FFC2000 V1073

Contents

Download Pdf Manuals

Related Search

Related Contents