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User`s Manual - GMW Associates

1. Difference highest lowest NMR frequency values expressed in ppm of the central NMR frequency value If no value is available lt CR gt lt LF gt are returned Number of NMR probes measurement points Geneva Switzerland User s Manual METROLAB Instruments SA MFC 3045 User s Manual 8 6 STATUS AND ERRORS The MFC 3045 has 6 status registers to show event or error conditions or states of the instrument 8 6 1 STATUS 1 The Status register 1 shows event and error conditions When a condition occurs the corresponding bit is set to 1 The bits are cleared to O after reading the status register command ST1 eee I pel O E IO reset or No NMR Sig Miscel error Remote Com Modulation Command Data ready power on seen on button munication error error probe s changed state error bit 7 reset or power on This bit is set to 1 at power on or following a reset of the instrument bit 6 No NMR signal seen This bit is set to 1 to indicate that one or more probes measurement points have not seen any NMR signals bit 5 Miscellaneous error This bit is set to 1 when at least one of the bits 2 4 or 5 of the status 4 is set to 1 bit 4 Remote button changed state This bit is set to 1 to indicate that the button of the Remote Box has changed state button pressed or released bit 3 Communication error This bit is set to 1 when at least one of the bits 4 to 7 of the status 5 is set to 1 bit 2 Modulat
2. Built in aluminum can be adapted to most cryostat magnets METROLAB Instruments SA Geneva Switzerland 59 MFC 3045 User s Manual 60 Geneva Switzerland METROLAB Instruments SA MFC 3045 User s Manual 10 APPENDIX FIELD MAPPING FIELD MAPPING AND SHIMMING MRI MAGNETS WITH THE METROLAB FIELD ALIGNER Prof Guy AUBERT Grenoble High Magnetic Field Laboratory One of the major requirements for efficient Magnetic Resonance Imaging MRI is a high enough quality of the magnetic field generated by the main magnet system The goals for the quality of the field of a whole body MRI magnet are typically 1 Time stability in the 1 ppm range at least 2 Space homogeneity or uniformity within a few ppm in a roughly spherical volume 50 cm in diameter Achieving time stability could be difficult for resistive magnets but is usually not a problem for permanent magnets or superconducting ones operated in the persistent mode provided that no ferromagnetic pieces are moving in the vicinity of the magnet On the contrary due to imperfections of the magnet itself and to environment effects the required homogeneity is never obtained without using sophisticated correction systems often referred to as shims This recalls the small pieces of iron which were stuck by the pioneers of the NMR on the pole pieces of their iron core magnets in order to improve the homogeneity of the field Even if the magnet system is provided with a con
3. NB This decomposition is unique and does not depend on the size of the device carrying the probes which has been chosen to fit in most of the magnets It is mathematically valid for any point inside the biggest magnetically empty sphere that can be found with the chosen center O The value of the scaling radius rg is only a question of convenience it can be changed by the operator and the corresponding results redisplayed For an easier interpretation it should be set as the radius of the user s sphere of interest However the accuracy of the mapping of the field by the calculated expansion will be lower at a distance from the center O significantly bigger than the average radius of the probes holder IV SHIMMING After having qualified the field plotting and the decomposition process the set of coefficients thus obtained can be used to determine an appropriate shimming Different situations have to be considered 11 Active shimming with a set of correcting coils the characteristics of which are or are not well known by the user 12 Passive shimming with a possibly great variety of elements In any of these cases or sub cases an additional package can be proposed with its specific documentation KKK K KKK KKK 68 Geneva Switzerland METROLAB Instruments SA MFC 3045 User s Manual TABLE I n m 0 1 2 3 4 5 6 0 kkkkkkkk 1 000000 1 0 000 90 000 1 000000 1 000000 2 0 000 45 000 90 000 1 000000 750
4. will be infinite To avoid that enter a value in dHz no decimal dot in the Target Value box i e the value measured by the probe 1 Geneva Switzerland METROLAB Instruments SA MFC 3045 User s Manual 7 MFC 3045 FIRMWARE UPDATE In order to keep the MFC 3045 system up to date the Memory containing the FirmWare of the system can be updated with a newer version The latest version is available on the Internet at address http www metrolab com The FirmWare file is a Motorola format ASCII file Once it is downloaded to the user s PC it can be loaded into WMFCtool by clicking on OPEN FW FILE button in the Update FirmWare window available through the Advanced menu The present version of the MFC 3045 FirmWare and the version of the FirmWare file are both displayed on the screen The MFC 3045 FirmWare will be updated by clicking on the UPDATE button The process can take several minutes and a scrolling bar indicates it If for any reason the system fails during the update of the FirmWare i e power lost The process has to be started again But because the FirmWare memory has been deleted the MFC 3045 runs with a minimal boot firmware This means that the RS 232 parameters has to be set at their default values in WMFCtool So first go to the Configuration window check the Advanced Options box if it is not done and click on the RESET TO DEFAULT button Then exit the Configuration window and select ABOU
5. XX The string must be send again The MFC 3045 will return ZZ in case of fatal error In that case the MFC 3045 will stay in Update mode even after switch off until the FirmWare is correctly programmed Only a correct end of file in the MOTOROLA format will terminate the Update mode Note This command is valid only for FirmWare version 2 00 or higher Commands only available as Advanced commands level 1 or more Commands only available as Advanced commands level 2 Value can be changed in the EEPROM Advanced commands level 2 MFC 3045 User s Manual 8 9 PROBE ARRAY NORMALISATION amp EEPROM Some settings specific to the Probe Array or the Main Unit are stored in a non volatile memory EEPROM At the time the MFC 3045 is switched on or reset the contents of the EEPROMs are stored in the RAM of the MFC 3045 to be used by the system Some of these settings can be changed when the MFC 3045 is in advanced mode level 2 However the change affects only the RAM memory and will be lost if the MFC 3045 is switched off or reset The settings in RAM can be copied into the EEPROM using the command SMU for the Main Unit or SPA for the Probe Array All the changes will be then permanent and restored the next time the MFC 3045 is switched on As explained in section 2 4 page 8 and section 6 4 page 28 the Probe Array has to be normalised by measuring every probe in the same magnetic field The discrepanci
6. the corresponding line in the table and then clicking again RUN REDO or pressing the Start button of the Remote Control box But do not forget to put the Probe Array on the corresponding position on the guide After the last measurement is done The Target value which is the mean value of the whole set of probe measures is indicated This Target value will be used to calculate for each probe the correction value saved in the Probe Array EEPROM It will also be used to calculate the remaining errors during the verification process When all probes have been measured the EXIT button become available Quit the Normalisation window by clicking on it This will save the correction table in the EEPROM of the Probe Array At any time pressing the lt ESC gt key or clicking on the CANCEL button quit the Normalisation window but no data will be stored and the measurements are lost 30 Geneva Switzerland METROLAB Instruments SA MFC 3045 User s Manual 6 4 3 3 Verification This window allows to verify and if necessary to modify the result of the Probe Array normalisation The process is the same as for the normalisation the Probe Array is put on the position 1 of the positioning guide and the measurement is done with the RUN REDO button or the Start button of the Remote Control box Then this sequence is repeated until all the probes of the array have been measured In the Verification window the main table show
7. 63 MFC 3045 User s Manual 8 ro is a reference radius which makes it possible to scale the coefficients H IM and J of the expansion For evaluating quickly the quality of the magnet it is convenient but not compulsory to take the radius of the sphere of interest as rq 9 P cos and PM cos are the Legendre and associated Legendre polynomials in os NB The P cos that we use do not include the EN Hobson s factor 10 W is a numerical weight factor which forces the product WM PM cos6 to oscillate in the range 1 1 in order to give a straightforward physical meaning to the corresponding coefficients K and JM As an illustration of the interest of this weight factor let us consider for instance the signification of the coefficient 14 P cose is maximum for 6 1 2 and the corresponding value is 105 Suppose that for some magnet 1 is found to be 2 ppm for rg 25 cm in an expansion which does not include any weight factor that is w 1 This magnet could appear at first sight better than it actually is Indeed the meaning of E 2 ppm is that the Bz difference between the point at 25 cm from the origin along Ox for instance and B at the origin is 105 X 2 21 ppm of Bo If a weight factor wi 1 105 is included in the expansion the corresponding 1 is no longer 2 ppm but 21 ppm which gives immediately an indication of the influence of this term There are several possible choices for the we
8. 7 MFC 3045 User s Manual 2 4 PROBE ARRAY TYPE MFC 3048 The Probe Array is usually a custom design for which the shape type half moon circle sphere or cylinder the number of probes their geometrical distribution and the general overall dimensions are defined for the customer use Figure 8 Partial view of a Half Moon type Probe Array with a part of cover removed showing probes However Metrolab proposes several types of standard half moon type Probe Arrays with 13 to 24 probes and nominal diameters of 300 to 500 mm according to the following table These Half Moon Probe Arrays are placed on a probe holder MFC 3049 which fits to the magnet inner shape This permits the half moon Probe Array to be rotated around the magnetic field axis with 12 16 24 32 or 36 angular positions per turn 3D type Probe Arrays spherical or cylindrical are intended to realize a complete mapping without any displacement of the Probe Array The advantage is that of a shorter measuring time compensated by a smaller final number of measures i e a smaller spatial resolution When connected to the MFC 3045 Main Unit the Probe Array data may be read in the control PC It contains an EEPROM memory programmed with all the specific data of a Probe Array including central frequency minimum amp maximum measuring frequencies number of probes and other useful functional data such as the correction table This correction table is the result of the
9. Statuses Summary Modulation parameters Pages Modulation Amplitude Modulation Central Frequency Modulation Lowest Frequency Modulation Highest Frequency Modulation Reference parameter Modulation period Number of steps for ramp modulation Number of steps for plateau modulation DDS Bit resolution Status and Errors Status Register 1 Status Register 2 Status Register 3 43 44 45 46 47 48 50 sn ST2 ST3 ST4 STS ST6 ERR SMA modulation parameter error Measurement status Status Register 4 Miscellaneous status Status Register 5 B R amp communication error Status Register 6 Communication settings Return last Command Error Send message automatically 37 37 37 37 37 Probe Array 51 51 51 51 51 Measurement parameters NPR 38 DCH 38 PLP 38 PHF Number of measurement points NMR probes Probe Array Central Frequency Probe Array Lowest Frequency Probe Array Highest Frequency RF harmonic NCY NO NET Number of measurement or modulation cycles Number of preliminary cycles Time duration of preliminary cycles RSO Rejection Signal Offset 38 REH RSG Rejection Signal Gap 38 NST RSP NMR Signal Threshold 51 Advanced commands Reset the system Version Serial Numbers LED Remote Box busy LED control 53 DFF DDS fixed frequency 53 FSW Frequency Sweep 54 5 A
10. Table CBT Field Value BFY Mhz 20 42 2997215 0 021 42 2997210 0 033 42 2997206 0 043 42 2997223 0 002 42 2997248 0 057 42 2997243 pee H 3 o o 20 1 2 3 3 7 mn N Figure 23 Verification window during measurements METROLAB Instruments SA Geneva Switzerland 31 MFC 3045 User s Manual Verification of Normalisation Correction value Target Value dHz 3 422997224 Graph BFV Target ppm DA 1 2 es 3 2 Fels if H O Reagy Keel Probe Figure 24 Graphical display of remaining errors in ppm After all the measurements are done check that all remaining errors BFV Target ppm are in the range of 0 5 ppm peak to peak This can be easily seen on the graphic labeled Graph BFV Target ppm If either one or a few points are erratic it is possible to correct it or them Erratic point may be due to a magnetic or electrical perturbation or a mistake on the Probe Array position during the normalisation or verification measurement s of the relevant probe s In that case select the erratic probe with a mouse click on its line in the table Numeric Results The line will be yellow highlighted If the graph of remaining errors BFV Target is displayed the erratic probe can be selected using the up and down arrows on the right side of the Probe indicator Then put the Probe Array on the corresponding pos
11. The conversion factor to the Tesla units is the y factor Y 42 576255 MHz T METROLAB Instruments SA Geneva Switzerland 1 MFC 3045 User s Manual 1 2 PRINCIPLE OF OPERATION The system is mainly composed of two units 1 MFC 3045 Main Unit 1 MFC 3048 Probe Array The MFC 3048 Probe Array is the sensing unit of the system and it is placed in the magnetic field to be measured The system must be connected to a host computer to be operated The communications are supported by an RS 232C link LabView MFCTOOL software running under Windows NT or 95 is provided with the system and gives the user easy access to the operation of the system The description of all operation commands is given in this user manual The main operation functions are as follows e The user can modify the measurement parameters e The Radio Frequency signal sent in parallel to all NMR probes is modulated in order to produce the NMR signals frequency modulation e An individual electronics storage records all NMR signals of each probe e The validity of all NMR signals of each probe is checked The missing and noisy signals are then rejected e The average NMR frequency value field value its standard deviation over all measurement cycles as well as the number of cycles giving NMR signals are available for each NMR probe The central and extreme NMR frequencies over all measurement points are also given e The optional analysis software MFC 3050 cal
12. Then execute SETUP EXE located in the root directory of the CD ROM or the diskette 1 Note that with CD ROM media the setup program should start automatically 4 3 USING WMFCTOOL WMFCTOOL is user friendly using menus and windows that allow the user to reach the desired mode of operation by a mouse click or by using the Function Key using only intuitive decision and no code or written command In addition a color coded window system simplifies decisions e Blue Fields that can be modified sequence changing frequency values etc e Red Indicates values that cannot be changed e Green Going forth or back in a sequence e Exit or Break button stops the running sequence or exits current window At exit WMFCTOOL saves the configuration and settings in a file so the next time WMFCTOOL is executed all settings are restored automatically When starting WMFCTOOL the user gets into the Main Menu start point of all operations 4 4 MENUS AND COMMANDS 4 4 1 Main menu As shown in Figure 11 below There are 7 buttons Parameters allows the definition of the measurement parameters Measurements allows the selection of the different measurement modes starts the measurements and displays the data value for each probe with a calculation of mean and standard deviation Data Display displays the data on two different forms table of values or graphically Previous measurements stored into files can be also loaded and displayed Configuration allow
13. Y NMR Probe Correction Field Tab INb of writing 6 ID ROM version 3 char 1 0 WRONG VALUE s CAN Probe Array S N 15 char 480244 Dev Al RENDER THE Creating Date DD MM YY 16702700 Calibration Date DD MMAYY PROBE ARRAY OR MAIN eawn Cem owest Frequency dHz UNIT UNUSABLE a casan Central Frequency dH2 Highest Frequency dHz 651400000 Nb of Harmonic 3 pp 1000 Figure 17 EEPROM Utilities window 5 4 ADVANCED FUNCTION UPDATE FIRMWARE This window is used to maintain the MFC 3045 FirmWare up to date The process of updating the MFC 3045 FirmWare is fully described in Chapter 7 page 33 24 Geneva Switzerland METROLAB Instruments SA MFC 3045 User s Manual 6 MFC 3045 CALIBRATION PROBE ARRAY NORMALISATION 6 1 GENERAL The procedure described below corresponds to the calibration of the Main Unit MFC 3045 and the normalisation of the Probe Array MFC 3048 The calibration of the Main Unit MFC 3045 as well as the Probe Array normalisation must be done every 12 months These two calibrations can be performed separately of sequentially For the Main Unit the calibration consists only in verifying and adjusting the reference frequency of the local quartz oscillator if necessary The Probe Array does not need to be calibrated against a standard as the NMR signal results of a physical phenomenon and canno
14. a non volatile memory This means that if the RS232 parameters such as Baud Rate number of bits etc of the PC do not match the RS232 parameters set in the Main Unit MFC 3045 the communication will no longer be possible To restore the communication the PC must be set to 9600bd 8bits 1stop bit no parity no hard or soft handshake the default RS232 parameters of the Main Unit To reset the Main Unit to these default parameters the user must 1 push and hold down the Start button 2 push briefly the reset button i e with a pencil The Busy LED will blink about 8seconds then switch off Only at that time may the Start button be released The default RS232 parameters are then restored in the Main Unit MFC 3045 If the Start button is released when the Busy LED is still blinking the previous RS232 parameters are kept 2 6 SOFTWARE PACKAGE In addition to the System physical elements a software MFCTOOL for Windows WMFCtool is supplied This enables a PC connected to the serial port of the Main Unit MFC 3045 to display and control all the functions and parameters of the system It also enables the recording of measurements in files that allow the user to quickly obtain information about field value homogeneity and stability of the controlled magnet This software provides two types of communication access to MFC 3045 e An intuitive and easy to use program allowing the establishment of measurement parameters and command measuring se
15. file format It is also in the Configuration window that the Advanced mode can be enabled FC tool for Windows Figure 11 Appearance of the Main Menu of WMFCTOOL 4 4 2 Configuration window The window of the menu Configuration can be seen in Figure 12 When the Configuration window is opened the RS232 settings are dimmed To access them the Advanced Option box must be enabled and the password given The password can be modified if necessary This action will also enable the button ADVANCED in the main menu allowing access to Low Level commands Calibration tools EEPROM utilities and FirmWare update The Default directory will be proposed by default each time a file has to be saved or loaded Use the BROWSE button to select a different one WARNING Once the directory is selected use the button Select cur dir to validate the new selected directory DO NOT USE the Save button 14 Geneva Switzerland METROLAB Instruments SA MFC 3045 User s Manual The File Format switch allows the user to select the file format of the measurements In the MFC 3035 mode the data files are compatible with those created using a MFC 3035 system with MFCTOOL dos version The resolution of data is the Hz In the MFC 3045 mode the data are saved in file with one more digit dHz Configuration Serial Port Baud Rate HW Handshake Parity Stop bits COMI v 3600 Ru RS No Party RW ib W Data bits Wr Rd d
16. number of coefficients involved N 32 and 98 respectively In both cases the number Np of measured points is equal to this number and the decomposition software allows to fit the data with any number of coefficients lower or 66 Geneva Switzerland METROLAB Instruments SA equal to it This possibility is very important as a self test of the validity of the decomposition II FIELD PLOTTING AND DECOMPOSITION One of the key points of the problem is the positioning of the Ny measured points These positions must lead to the best conditioning of the matrix of the linear system to be solved together with the least sensitivity of the result to possible imperfections in the positions or in the measurements themselves This is not a trivial mathematical question but we have solved it and the Np NMR probes of our systems are placed according to this optimal solution The device carrying the NMR probes is fitted into the magnet bore by means of adjustable legs The minimum diameter of the bore is about 50 cm and the maximum one can be far more than 100 cm if necessary The bore does not need to be cylindrical which allows the system to be installed for instance in a magnet already equipped with its plastic cover and the patient bed Reference marks can be taken for further installation in the same position The origin or center and the z axis of the device must coincide at best with the corresponding elements of the principa
17. occurs provided it is enabled by the command SMA whether the corresponding bit in Status register is read or not i e the DR message Data Ready will be sent each time a measurement is finished and Data are ready even if the Status 1 is not cleared The parameter x of the command SMA is acting like a mask To enable an automatic message the corresponding bit of the mask must be set to 1 Examples e SMA 0O masks all the conditions and no messages will be sent SMA 255 maximum value allows any of the conditions when it occurs to generate its message automatically SMA 73 masks all the conditions except Remote box button released Communication error and Data Ready 64 8 1 METROLAB Instruments SA Geneva Switzerland 49 MFC 3045 50 Status Register 1 Returns the status 1 in binary form 8 ASCII characters 0 or 1 Bits are cleared after reading Status Register 2 modulation parameter error Returns the status 2 in binary form 8 ASCII characters 0 or 1 Bits are cleared after reading except bit 7 If one of the bits of status 2 is set to 1 the bit 2 of status 1 is set to 1 Status Register 3 Measurement status Returns the status 3 in binary form 8 ASCII characters 0 or 1 Status Register 4 Miscellaneous status Returns the status 4 in binary form 8 ASCII characters 0 or 1 Bits 2 4 to 7 are cleared after reading If bit 2 6 or 7 is set th
18. on the position 1 of the positioning guide The user must take care that the modulation parameters are correctly set A single measurement is a good way to check that but be aware that some probes will probably give 0 zero values because the Probe Array is not centered in the magnetic field only probe 1 is So check the value measured by the probe 1 and adjust the Modulation Central Frequency on that value Modulation amplitude of 1000 ppm is recommended as well as 60 modulation cycles Now the system is ready to begin the normalisation process After the first measurement the Probe Array is moved to the next position and so on until all the probe of the array have been measured at the same place in the magnetic field 6 4 3 The normalisation process During the normalisation process as well as the verification the measurements are performed with the modulation parameters correctly set See above In the Calibration menu there are three buttons for the Probe Array normalisation The function of each of these is described below 6 4 3 1 Measurements order This procedure is optional It is used only when for calibration facility measurements are performed in a sequence different from the normal numeration of the probes corresponding to the Number displayed on the positioning guide for each position The left column of the table corresponds to the sequence of measurements of the normalisation process The right column is the probe
19. or more METROLAB Instruments SA Geneva Switzerland 55 MFC 3045 User s Manual CBT r CET CET x Calibration Probe Selection After a measurement this command takes the value of the magnetic field without correction measured by the probe Px and puts this value in a table in the RAM of the MFC 3045 After measurement of all probes of the Probe Array at the same magnetic field the table is full and the next step of the Probe Array normalisation can be done x 1 to NP selects the value measured by the probe x and puts it in a table x 0 clear the table x any value gt NP calculates and sends back to the PC the average in decihertz dHz of all values in the table This can be used as target value for the calibration table see command CBT No parameters The table is read by the PC sequentially or in block depend of the command BLK Calibration Build Table When all the probes have been measured and selected using the command CPS this command creates the calibration table It does so by calculating the difference between the target value given by the parameter x in decihertz dHz x must be bigger than NP which is always the case in practice and each value of the table done with the command CPS The new calibration table will become permanent only after the command SPA gt EEP has been executed x 1 Copy the content of the calibration table
20. stored in EEPROM into the RAM of the MFC 3045 x 0 Clear the calibration table in RAM x gt NP Use x in dHz as the target value to create the calibration table No parameters The table is read by the PC sequentially or in block depend of the command BLK fr 1 to NP send back to PC the value of the correction for the probe r Set also a pointer on that probe for the command CET see below Calibration Edit Table This command allows to edit the correction table by writing the value x in the entry of the correction table corresponding to the probe pointed by the last command CBT r see above Without parameter CET returns the correction value for the probe selected by the last command CBT r see above Note The edited calibration table will become permanent only after the command SPA gt EEP has been executed Commands only available as Advanced commands level 1 or more Commands only available as Advanced commands level 2 NP Number of NMR probes measurement points 1 NP or 0 or any value gt NP 37768 37767 Geneva Switzerland METROLAB Instruments SA MFC 3045 User s Manual Calibration Date of Probe Array This command allows the user to write the calibration date of the Probe Array d must be a decimal number in the form jjmmyy Example if the calibration date is June 9 1998 the command will be CDP 090698 Note The
21. the Y axis R If you want the graph to autoscale either of the axis continuously click the lock switch DR shown at the left to lock autoscaling On pny By using the Scale Format buttons shown at the left you can maintain control of the y 43 format of the X and Y scale respectively Not used This button has no effect D If you press the Panning button shown at the left you switch to a mode in which you can scroll the visible data by clicking and dragging the plot area of the graph Geneva Switzerland METROLAB Instruments SA MFC 3045 User s Manual If you press the Zoom button show at the left you can zoom in or out on the graph If 2 you click on the Zoom button you see a pop up menu to choose the methods of zooming A description of each of the methods follows aa Zoom by rectangle Click on the area of the plot you want to zoom and drag the rectangle When the mouse button is released the zoom is performed a Zoom by rectangle with zoom restricted to X data the Y scale remains ad unchanged or to Y data the X scale remains unchanged FO Undo last zoom Resets the graph to its previous setting Zooming in about a point If you hold down the mouse on a specific point the di graph continuously zooms in until you release the mouse button lt Shift gt clicking zooms in the other direction Zooming out about a point lf you hold down the mouse on a specific point the Ba graph continuously zooms out until yo
22. to 1 to indicate that the received character does not have a valid stop bit s Reading the status clears this bit bit 5 Parity error This bit is set to 1 to indicate that the received character does not have correct parity information and is suspect Reading the status clears this bit bit 4 Overrun error This bit is set to 1 to indicate that additional character arrives when the RS232 input buffer is full Therefore the previous character is lost This will not happen if soft or hard handshake is used Reading the status clears this bit bit 3 Check Sum error This bit is set to 1 when the check sum of configuration data received in one hexadecimal block see Probe Array calibration chapter does not match the check sum value sent with the data block Reading the status clears this bit bit 2 to 0 RS232 Baud Rate These bits indicate the selected RS232 Baud Rate bit 2 bit 1 bit 0 Baud Rate 0 0 0 2400 0 0 1 4800 0 1 0 9600 lt Default value 0 1 1 19200 1 0 0 28800 1 0 1 38400 1 1 0 57600 1 1 1 115200 METROLAB Instruments SA Geneva Switzerland 47 MFC 3045 User s Manual 8 6 6 STATUS 6 Communication settings The Status register 6 reflects the communication RS232 settings GE E E ee Hardware Software Odd Even Parity set 1 2stop 7 8 bit s handshake handshake parity bit s Ve RTS CTS Xon Xoff bit 7 and 6 Always 0 bit 5 Hardware handshake This bit is set to 1 when the hardware handshake R
23. window allowing the user to read display and print the results of a measure It is possible to use Data Display window to look at a previous measure or set of measures as this window does not require communications with the MFC 3045 system So the Main Unit may be On or Off or even absent The data are available in ASCII and in graphical form Use the blue pull down selector in the upper left corner to select the different kind of display format The buttons Low Level Commands and Measurements are a short cut to their respective window Note that the Low Level Commands button is visible only if the Advanced Options have been enabled The button Print can be used to print the data on the default printer The button Load opens a window to choose a MFC3045 data file either a DAT or DAM file The button Exit will quit the Data Display window and go back to the Main Menu When the data of a Mut measurements DAM are displayed graphically a selector located at the bottom of the window is used to select which measurement is displayed Click on the measurement to be displayed Use the lt shift gt key while clicking to select more than one measurement You can lt shift gt click and drag the mouse through the list to select quickly several measurements The curves are displayed in different colors to enhance the readability The corresponding color of each curve is indicated on the left of Measurements selector METROLAB I
24. with a parameter is a Write command In most cases unless otherwise notified the Read command allows the user to read back the actual value setting of the command The MFC 3045 is not case sensitive and all the commands can be in either upper or lower letters Some commands are called Advanced commands which means that they are available only after the Advanced mode has been enabled using the ADV command The advanced commands are special commands that are not needed in regular operation The range of setting of some regular commands is extended when the advanced mode is enabled There are two levels of Advanced mode see description of command ADV the second level allows the users to modify the settings stored in non volatile memory EEPROM of the Probe Array or Main Unit Good understanding of the system is necessary before modifying the EEPROM settings The advanced modes do not correspond directly with the advanced menu of WMFCTOOL The next sections describe all the commands of the MFC 3045 firmware The following conventions are used indicates typical values can be different indicates commands only available as Advanced commands level 1 or more indicates commands only available as Advanced commands level 2 indicates that the setting can be changed in the EEPROM if Advanced mode level 2 is enabled P A indicates that the setting depends of the Probe Array NP_ indicates t
25. 000 1 000000 3 0 000 31 091 54 736 90 000 1 000000 688530 721688 1 000000 4 0 000 23 878 40 893 60 000 90 000 1 000000 660016 642857 710411 1 000000 5 0 000 19 416 32 866 46 911 63 435 90 000 1 000000 643525 604144 623187 04361 1 000000 6 0 000 16 371 27 542 38 826 51 123 65 905 90 000 1 000000 632774 580952 578970 612182 700591 1 000000 7 0 000 14 157 23 730 33 222 43 202 54 292 67 792 1 000000 625212 065456 551899 564500 605143 698017 8 0 000 12 474 20 858 29 076 37 542 46 603 1 000000 619603 954355 033519 034874 955073 9 0 000 11 149 18 613 25 872 33 253 1 000000 615278 546004 520184 014526 10 0 000 10 080 16 808 23 316 1 000000 611841 039491 510050 11 0 000 9 198 15 324 1 000000 609045 034267 12 0 000 8 459 1 000000 606725 13 0 000 1 000000 n m 0 1 2 3 4 5 6 METROLAB Instruments SA Geneva Switzerland 69 MFC 3045 User s Manual TABLE II 3 2 z 32 x y 5 P y Ha 4 70 Geneva Switzerland METROLAB Instruments SA MFC 3045 User s Manual TABLE II nim 0 2 3 4 5 6 r pe ae 1 2 mu 3 Uu Ji 2 5 6 9 7 10 n m 0 1 2 3 4 5 6 METROLAB Instruments SA Geneva Switzerland 71 MFC 3045 User s Manual Personal notes 72 Geneva Switzerland METROLAB Instruments SA MFC 3045 User s Manual Personal notes METROLAB Instruments SA Geneva Switzerland 73 Low Level Commandes and
26. 16 4 4 4 1 Elements of the Measurement window common to all Run modes oo0nnnnen0esooo0000eeee 16 4 4 4 2 The different Run Modes 17 4 4 5 Data Display windom eenaa eaaa a a e aaae A a ae ae ATA aa Aa ATEA AE 19 METROLAB Instruments SA Geneva Switzerland I PART B Technical Topics 5 The Advanced MBNUeccncnccnnnnnnnnnncnnnnnnnnnn acc 23 5 1 Advanced function Low Level Commands Window ssesssessssstesssestrirtrttsetttirnrttseetttrtnnnneeenennne 23 5 2 Advanced function Calibration oooocccnnnnnnnccocccccnncnonanonancnnnnnnnnnnnnnnnnnnncnnnnnnnnnnnnnnnrnnnnnnnnnnnnnc rn nnnnnnncno 23 5 3 Advanced function EEPROM U lties A 23 5 4 Advanced function Update FirmWare occcccocococccnncccnnnanannnnnnncnonnnnnnncnnnnnnnnnnnnnnnnnnnncnnnnnnnnnnnnnnnnnnnnes 24 6 MFC 3045 CALIBRATION PROBE ARRAY NORMALISATION une 25 6 1 GENERA EE 25 6 2 Using WMFCtool for cGalbratton nn rr 25 6 3 Main Unit Calibration ue 27 6 3 1 Necessary components IIA nae 27 6 3 2 The calibration Drocesg EE 27 6 4 Probe Array NORMALISATION cccccccccceeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeseseeeeeeeeeeeeeeeeeeeeeeees 28 6 4 1 Necessary COMPONEN S cui id a a it 28 6 4 2 Physical installation Of probe aa 28 6 4 3 The normalisation process oooooocccnnncococccnnncononanonnccnnnnnnnnnnnrn cnn nan n rra n cnn narran rre n nn rra 29 6 4 3 1 Measurement order 29 6 4 3 2 Normalisation of Probe Array eesee
27. 45 42 NP Number of cycles giving NMR signals not discarded for each measurement point The values are returned according to the Data Reading Mode see section 8 5 1 above If no value is available lt CR gt lt LF gt are returned There are 4 hexadecimal characters for each value when in Hexadecimal Block Mode BNC is not available in Continuous measurement CTN Individual NMR frequency values in decihertz dHz for the selected measurement point see commands RUN or SRC There are two values per modulation cycle and the values are returned according to the Data Reading Mode the up value before the down value The Random access mode is not available If no value is available lt CR gt lt LF gt are returned There are 8 hexadecimal characters for each value when in Hexadecimal Block Mode BIN is not available in Continuous measurement CTN Central NMR frequency value in decihertz dHz This is the central not average value of all measurement points giving NMR signals If no value is available lt CR gt lt LF gt are returned Lowest NMR frequency value in decihertz dHz This is the lowest measured value over all measurement points giving NMR values If no value is available lt CR gt lt LF gt are returned Highest NMR frequency value in decihertz dHz This is the highest measured value over all measurement points giving NMR signals If no value is available lt CR gt lt LF gt are returned
28. 5 D version 1 10 9 day all probes simultaneously 5 seconds typical RS 232C 10 to 40 C 20 C to 70 Non condensing is stated 0 2 Tesla 270 x 210 x 75 mm 3 kg 9 2 POWER SUPPLY UNIT MFC 3046 Power requirement 40VA Universal from 85 to 240 AC Volts 50 60Hz Dimensions 210 x 120 x 50 mm Weight 1 5 kg Cable length from power supply to Main Unit 10 meters 9 3 PROBE ARRAY MFC 3048 Probes are tuned to one dedicated frequency Frequency range typically 2 Possible tuning frequencies 3 4 to 300 MHz Probe position accuracy better than 0 3 mm Discrepancy between probes put in the very same magnetic field max 0 2 ppm Cable attached to the Probe Array 3 meters The number of probes as well as the array diameter are customer defined On the request of the user any geometry can be considered and implemented The total number of NMR probes is limited to 96 Deconvolution Mathematical Software MFC 3050 The analysis software MFC 3050 gives the spherical harmonics coefficients of the measured field The analysis software gives the maximum information when it is used with a Metrolab spherical geometry Probe Array In this case the number of coefficients can be equal to the number of measurement points 9 4 ROTATING PROBE ARRAY HOLDER MFC 3049 Mechanical device designed to hold the half moon Probe Array and to rotate it inside the magnetic field with a selection of 12 24 36 16 or 32 increments per turn
29. DV RST VER S N 53 53 53 53 RUN SRC CTN HNT BRK 39 39 39 39 39 1 Starts a measurement Search over full range of Probe Array Continuous measurement Hunt Mode Breaks Data Reading Data transfer Block Mode 4 Read Magnetic B field value 41 Read Standard deviation 41 Read Number of valid cycles 41 Individual probe NMR frequency val 41 Central NMR frequency value 41 Lowest NMR frequency value 41 Highest NMR frequency value 41 Difference highest lowest NMR frequency values 41 BLK BEV BSD BNC BIN BFC BFL BFH BFD Calibration and EEPROM Pages Settings of Main Unit 5 Settings of Probe Array 55 Correction table Probe Selection 56 Correction table Build Table 56 Correction table Edit Table 56 Calibration Date of Probe Array 57 Calibration Date of Main Unit 57 Lor for ADVanced level 1 or for ADVanced level 2 Read command gt XYZ Write command gt XYZ bit 7 Hexa 80 Com munication error Remote button changed state No NMR Sig seen on probe s Modul param Command error Modulation error reset or power Status 1 On Miscel error Data ready Status Registers RS232c settings P A not SOS exceed DDS range Status 2 Allowed lost cycle reached Cycle lost Period not stable Max amplitude reached Period
30. METROLAB Instruments SA MFC 3045 MAGNETIC FIELD CAMERA User s Manual Included MFCtool for Windows V8 0 Version 2 00 Revision 1 5 February 2000 110 ch Du Pont du Centenaire CH1228 GENEVA SWITZERLAND Tel 41 22 884 33 11 Fax 41 22 884 33 10 Web http www metrolab com E mai contact metrolab ch MFC 3045 User s Manual CONTENTS PARTA Using the MFC 3045 T INTRODUCTION did 1 EI General description iei e td 1 1 2 Principle of operationis ca e o nd ito 2 1 3 Measuring detailed procedure AEN 3 14 OPA MA as 4 2 SYSTEM DESCRIPTION aaa EOS 5 21 Genoralus TEE 5 2 2 Main unit Type MEC 2048 ENEE 5 2 3 Power supply type MEC 2048 ENNEN 7 2 4 Probe Array type MEC 2048 8 2 5 Remote Control DOK ege tddi 9 2 6 SOM PA o ea e aay ot 10 3 INSTALLATION uuu dalla alabada ad 11 3 1 Prope Aay ricino aed nated aed deo ied 11 3222 PEA de 11 3 3 Connections to main unit power supply and DC 11 3 4 OA e aa ea a ote 11 3 5 Software Setup uscar aida aia 11 de MECtooltor Windows MECH EE 13 SEH Gerald en eo 13 4 2 SOHO H ET 13 4 3 Using WMECTOOLE ao 13 4 4 Menus and Commande AAA 13 E EE 13 4 4 2 Configuration WINKOW iii EENEG added 14 4 4 3 Measurement Parameters wimdow ccccceeeeseeeeeeeeeeseeneeeeeeeetsesaaaeeeeeeeeesenaneneeeeeeesennaaeeees 15 4 4 4 Measurements WINKOW cccccccccessssneceeeesesenaceeeeeeesseesaaaeeeeeesseessaaaaeseeseseeeaaaaaeseseeseessaaaaeees
31. NMR frequency values one per valid modulation cycle see below The RMS is given in Hz with 0 1Hz resolution or 1Hz if the MFC3035 file format has been selected in the Configuration window e The number of valid modulation cycles On each modulation cycle two NMR signals are obtained one on the rising ramp and one on the falling ramp If this pair of signals is not in a given tolerance the value of that modulation cycle is discarded The number of valid modulation cycles is the total number of modulation cycle taking in account for the final field value See section 1 3 page 3 G The Run Mode selector allows choosing between 5 types of measurement described in the next section 4 4 4 2 The different Run Modes Single This mode performs a single measurement with the selected modulation parameters when the button RUN is clicked or when the Start button of the Remote Control box is pressed After the measurement is done it is possible to save the data by clicking the Save button Then the name of the file appears in the Measurement File indicator located in upper left corner of the window The default extension of the single file is DAT During the measurement the busy LED of the Remote Control Box is lit as well as the virtual LED in the Measurements window indicating that the Probe Array must not be moved An individual probe can be selected in Individual NMR point In that case the NMR frequency values given b
32. T in the Main Menu The message MFC 3045 Flash PROM erased should appear in the MFC 3045 Firmware version box That means that the RS232 communication is established Then go to the Update FirmWare window and try again to load the FirmWare file to update the MFC 3045 Once the FirmWare is successfully updated WMFCtool has to be started again MFC 3045 FW Version File Fy Version Programing Flash PROM E SS Figure 25 The Update FirmWare window during the process Note Only FirmWare Version 2 00 or higher can be updated with WMFCtool To update a lower FirmWare version the FirmWare memory inside the Main Unit must be replaced Le METROLAB Instruments SA Geneva Switzerland 33 MFC 3045 User s Manual 34 Geneva Switzerland METROLAB Instruments SA MFC 3045 User s Manual 8 MFC 3045 BASIC COMMANDS 8 1 GENERAL CONSIDERATIONS The MFC 3045 is controlled with a set of commands sent by a computer via a RS232 link An MFC 3045 command consists of 3 ASCII characters which are the command mnemonic followed by a terminator or followed by a comma then a decimal number the parameter and a terminator The terminator is either the 2 characters Carriage Return and Line Feed lt CR LF gt or a semicolon lt gt The semicolon terminator is used to send several commands on one line Generally a command without parameter is a Read Command meaning that the MFC 3045 sent back a message while a command
33. TS CTS is enabled bit 4 Software Xon Xoff handshake This bit is set to 1 when the software handshake Xon Xoff protocol is enabled bit 3 Odd Even parity This bit is set to 1 when the Even parity is selected cleared to 0 indicates the Odd parity This bit has no meaning if the parity is not enabled bit 2 0 bit 2 Parity set This bit is set to 1 to indicate that the parity check is enabled bit 1 1 2 stop bit s This bit is set to 1 when 2 stop bits are selected cleared to O indicates one stop bit bit 0 7 8 bit s length This bit is set to 1 when the RS232 data is 8 bits long cleared to 0 indicates 7 bits long 48 Geneva Switzerland METROLAB Instruments SA MFC 3045 User s Manual 8 6 7 Send Messages Automatically To avoid a continuous polling of the status register to check if data is ready or if an error condition has occurred the MFC 3045 can send automatically to the computer a message of 2 ASCII characters when given conditions occur The command SMA allows the user to select which one s of the 8 conditions will generate a message isc i Modulation Command Data Ready Conditions cation error error error released depressed Messe PA UP DN EE RS ME CE sent Correspond es 7 a status Bit 4 of Bit 43 of Bit 2 of a 1 of el 0 of to status 1 status 1 status 1 status a status el SMA parameter value The message of a given condition is sent each time that the condition
34. are returned in one block of data at the reception of a data reading command without parameter Each data consists of 8 or 4 ASCII characters of a hexadecimal number 0 9 A F There is no separator between values The check sum modulo 16 bits gt 4 characters is sent after the last data The check sum itself is not included in the check sum The number of character returned is Number of measurement points 8 or 4 see BNC command 4 check sum DEN returns the magnetic field values of all NMR probes plus a check sum into one hexadecimal block of data 40 Geneva Switzerland METROLAB Instruments SA MFC 3045 User s Manual 8 5 2 During a continuous measurement CTN The principle is the same as above except for a few differences and that only the magnetic field value can be read Standard Deviation and number of Valid Cycle are not available Data are not available at the end of the measurement but after each modulation cycle The differences are explained as follows a Random access BFV O returns the modulation cycle number since the beginning of the continuous measurement Then all values read using BFV x will be the measured value of that cycle To select the last completed modulation cycle send again the command BVF 0 b One by one Decimal and Hexadecimal block modes Only the values of the last complete modulation cycle are stored But once a data reading process is initiated the data are not updated unt
35. be Array Lemo 2p size 2 connector of the Main Unit can be measured with the external frequency counter Calibration of Main Unit Status Sending Fixed Frequency 10 000 000 MHz Figure 19 Main Unit calibration window The measured frequency must be 2Hz with the D option 10 000 000MHz lt 5Hz with the M option If the frequency is not in the tolerance the oscillator must be trimmed by removing the top cover of the Main Unit 10 M4 screws with a hexagonal male 3mm wrench and acting on the multiturn potentiometer placed on the side of the 20 MHz quartz oscillator as shown on photography below the D Decay option is a oven controlled quartz oscillator the M option is a temperature controlled quartz oscillator METROLAB Instruments SA Geneva Switzerland 27 MFC 3045 User s Manual JN A OOOO Figure 20 View of the 20 MHz Quartz oscillator and trimming potentiometer on its right Let the oscillator to stabilize before a new frequency measurement about 2 minutes then repeat the trimming operation if necessary After the calibration is done close the cover and leave this routine by clicking on the DONE button this will update the calibration date in the Main Unit EEPROM Press the lt ESC gt key or mouse click on the CANCEL button to not update the calibration date 6 4 PROBE ARRAY NORMALISATION 6 4 1 Necessary components The necessary components required to perform this ca
36. calibration date will become permanent only after the command SPA gt EEP has been executed CDP CDP d Calibration Date of Main Unit_ This command allows to write the calibration date of the MFC 3045 Main Unit d must be a decimal number in the form jimmyy Example if the calibration date is June 30 1998 the command will be CDU CDU d CDU 300698 Note The calibration date will become permanent only after the command SMU gt EEP has been executed Commands only available as Advanced commands level 1 or more Commands only available as Advanced commands level 2 an METROLAB Instruments SA Geneva Switzerland 57 MFC 3045 User s Manual 58 Geneva Switzerland METROLAB Instruments SA MFC 3045 User s Manual 9 SPECIFICATIONS 9 1 MAIN UNIT MFC 3045 Measurement principle Magnetic field range Absolute accuracy Resolution Frequency stability Aging Readings Mapping time Interface Operating temperature Storage temperature Humidity Magnetic environment Dimensions Weight NMR nuclear magnetic resonance of protons 0 08 to 7 Tesla better than 5 ppm 10 RF gt 10MHz or 0 1 Hz RF lt 10MHz 3045 M version 0 5 ppm over 5 to 50 C 3045 D version 0 1 ppm over 25 to 70 C Down to 0 03 to 0 05 ppm over a period of 3 days 3045 D version is appropriate for decay measurement The reference clock is an Oven Controlled Xtal Oscillator OCXO 304
37. cellaneous state and error conditions The bits 0 1 and 3 reflect present condition while bits 2 and 4 to 7 are cleared when the status is read When one of the bits 2 6 or 7 is set to 1 the bit 5 of status 1 is set to 1 E EE E EA E Ee EEPROM Remote Remote Overflow in Data in RAM Hardware EEPROM Main Unit success button button state creating calib lt gt problem EEPROM wrote changed state table EEPROM bit 7 Error with Probe Array EEPROM This bit is set to 1 to indicate an error in reading the Probe Array EEPROM Reading the status clears this bit bit 6 Error with Main unit EEPROM This bit is set to 1 to indicate an error in reading the Main Unit EEPROM Reading the status clears this bit bit 5 EEPROM successfully wrote This bit is set to 1 to indicate that the EEPROM either the Main Unit or Probe Array EEPROM has been successfully wrote Reading the status clears this bit bit 4 Remote button changed state This bit is set to 1 to indicate that the button of the Remote Box has changed state button pressed or released Reading the status clears this bit bit 3 Remote button state This bit indicates the state of the Remote Box button It is set to 1 when the button is released and cleared to O when the button is pressed bit 2 Overflow in creating calib table This bit is set to 1 to indicate that an overflow occurred when the MFC 3045 calculated the Probe Array calibration table That can happen if the refere
38. culates the spherical harmonics coefficients of the measured field It can be adapted to any Probe Array configuration e For optimized magnetic field analysis see annex at end of this manual MFC 3045 Main Unit MFC 3048 e Probe Counters NMR Probes Data Buffer Figure 1 Schematic representation of the MFC 3045 Measuring system 2 Geneva Switzerland METROLAB Instruments SA MFC 3045 User s Manual 1 3 MEASURING DETAILED PROCEDURE As previously stated measuring parameters define the number N of cycles of a measure for each probe of the Array This number corresponds to N frequency sweep cycles with a period T Normally for each frequency sweep resonance is detected twice once on increasing once on decreasing frequency The resonance position is detected by separate counters for the 2 signals Then the mean value of these 2 counts is used to calculate the real NMR frequency Frequency Up going f _requenc Down going f reguency A tl me NMR signal Time Figure 2 Description of NMR frequency detection and calculation At that point a decision of the measure s validity is made If no signal or only one signal is detected the measure of that cycle is invalid If the difference between up and down counts is superior to a normalized value established at factory for each Probe Array plus a margin of about 40 ppm the measure of that cycle is also considered as invalid This allows the sys
39. e RS 232 port to PC Probe Array connector maintenance connector Figure 5 View of the different connectors of the MFC 3045 6 Geneva Switzerland METROLAB Instruments SA MFC 3045 User s Manual 2 3 POWER SUPPLY TYPE MFC 3046 A separate power supply delivers the necessary voltages to the Main Unit via a 10 meters cable so that it can be installed near by the control PC The power supply accepts AC voltage in the range 90V to 264V 50 60 Hz Figure 6 View of the Power Supply MFC 3046 In fact the power supply delivers regulated voltages slightly higher than the required end voltages These voltages are then redistributed into the various zones of the Main Unit where they are set to the final voltage by local regulators with low voltage drop in order to minimize thermal losses The power supply is separated from the Main Unit because it cannot be in a magnetic field as it contains a transformer that will not work in magnetic fields greater than 0 01 Tesla The best place to locate the Power supply is near the PC This unit has an LED light monitoring the Power supply to the MFC 3045 system and a Reset button allowing a reset of the Main Unit from the PC control room All the functions of this unit can be seen on Figure 7 Reset Switch Power connector Power LED Fuse Holder Power Switch Mains cable receptacle Figure 7 View of the principal ports and commands of MFC 3046 METROLAB Instruments SA Geneva Switzerland
40. e bit 5 of status 1 is set to 1 Status Register 5 B R 8 communication error Returns the status 5 in binary form 8 ASCII characters 0 or 1 Bits 3 to 7 are cleared after reading If one of bit 2 to 7 is set the bit 3 of status 1 is set to 1 Status Register 6 Communication settings Returns the status 6 in binary form 8 ASCII characters 0 or 1 Command Error Returns the 3 first characters of the command that gave the last command error Send message automatically mask of the conditions that can send a message to the computer automatically SMA O masks all conditions no message is sent while SMA 255 allows all the conditions to send message to computer automatically Geneva Switzerland User s Manual METROLAB Instruments SA MFC 3045 User s Manual 8 7 PROBE ARRAY NPR x Number of measurement points NMR probes of the 1 32 64 or 96 Probe Array PCF x Probe Array Central Frequency This is the frequency in 2010 308010 decihertz dHz for which the Probe Array is designed This value is used as reference for most of the values expressed in ppm Probe Array Highest Frequency in decihertz dHz Above 2010 308 10 this frequency detection of NMR signals is not guaranteed RF harmonic The RF generator is limited to 44Mhz for 1 3 5 or 7 higher frequencies the Probe Array uses a odd harmonic of the fundamental RF up to harmonic 7 NST x NMR Signal Thre
41. e next button can be labeled START RUN or REDO e START means that a mouse click on the button will initiate something i e a multi measurement but will not do a measurement e RUN and REDO mean that a mouse click on the button will begin a measurement Pushing the Start button of the Remote Control Box can also do this action REDO is used in Multi mode to replace in the file a measurement previously done C Clicking on the EXIT BREAkK button will stop the measuring sequence or quit the Measurement window if no measurement is in progress D The Current Modulation Parameters table allows modifying the modulation parameters However the Reference parameter cannot be changed If necessary go back to the Measurement Parameters window Section 4 4 3 page 15 16 Geneva Switzerland METROLAB Instruments SA MFC 3045 User s Manual E The Measurement time indicator displays the total time in seconds needed for the measurement without the transfer time F The Results display is the area located above the Current Modulation Parameters table It is used to display the results of each measurement For each probe of the array the display shows e The measured NMR frequency in MHz This is the average of the values of all modulation cycles with a resolution of 0 1 Hz or 1Hz if the MFC3035 file format has been selected in the Configuration window e The RMS value is the standard deviation of all the
42. ed Let us first discuss the choice of M n If one makes M n n which seems to be self evident from a mathematical point of view the total number of coefficients is N 1 For N 7 the probable lower value for N this gives 64 quite a big number and for N 13 a desirable choice this gives 196 which exceeds certainly the economical possibility of using such a number of probes if one wants to avoid any moving part in the plotting device However it appears that the actual MRI magnets do not exhibit imperfections which need high order off axis terms to be described and this is fortunate enough since they would greatly complicate the shimming conventional shim coils do not allow corrections above m 3 and the passive shimming complexity grows very fast with the order Thus a much better choice is M n Min n N n which leads to a total number of coefficients equal to 215 N El N 1 where gt means the integer part of N 2 This gives only 32 and 98 coefficients for N 7 and 13 respectively Table III shows these examples of truncation and the corresponding numbering of the coefficients that we use We have now to choose N For good magnets N 7 should be sufficient and this value is consistent with the capabilities of the usual active shimming systems A more comprehensive choice is N 13 which should allow to meet most of the situations These two cases correspond to the prototypes MAP32 and MAP98 named by reference to the
43. ed in details in chapter 6 page 25 5 3 ADVANCED FUNCTION EEPROM UTILITIES To store the system settings there is a non volatile memory an EEPROM in the Main Unit as well as in the Probe Array The EEPROM Utilities window is used to read and modify the EEPROMS Press the READ EEPROM button to display the EEPROM s content in the window Use the pull down selector box located on the left above the table to select the Main Unit or Probe Array EEPROM METROLAB Instruments SA Geneva Switzerland 23 MFC 3045 User s Manual To modify a value click in the corresponding case of the table and edit it Click on the WRITE EEPROM button to store the modifications into the EEPROM WMFCtool always asks for a file name to backup the new data Then the data are written simultaneously in the EEPROM and in the file The SAVE FILE and LOAD FILE buttons are used to save the data in a file and to load a EEPROM data file into the table The WRITE EEPROM SAVE FILE and LOAD FILE buttons affect only the data of the EEPROM table displayed on the screen indicated in the EEPROM selector It is possible to enter comments in the Comment box but the line must start with a character The comments are saved in the data file only not into the EEPROM EEPROM Utilities Comments MFC 3048 PROBE ARRAY WARNING A GOOD UNDERSTANDING OF THE MFc 3045 SYSTEM IS NECESSARY BEFORE MODIFYING THE EEPROM L MEMORY _EEPROM Probe Array_
44. elay ms Default directory MITE Advanced Options File Format C Program Filestwmfctoo M OFF ON 9 MFC 3045 Figure 12 CONFIGURATION window If the RS232 parameters are changed at the time the Configuration window is closed using the EXIT button the RS232 parameters of the MFC 3045 Main Unit are changed accordingly It is strongly recommended to put a label on the Main Unit indicating the chosen parameters The new set of RS232 parameter is made permanent The Wr Rd delay can be increased to up to 100ms if the data sent by the MFC3045 seem to be garbled If for any reason it is no longer possible to establish the communication one can press the RESET L TO DEFAULT button and restore the default parameters of the MFC 3045 Main Unit by proceeding as follows e Push the Start button of the Remote Box and HOLD it down e Push briefly the Reset button i e with a pencil the Busy LED will blink about 8sec then will switch off e Only at that time the Start button can be released The default RS232 parameters are restored in the MFC 3045 Main Unit If the Start button is released when the Busy LED is still blinking the previous RS232 parameters are kept 4 4 3 Measurement Parameters window This window allows the setting of the measurement parameters such as the frequency parameters of the modulation RF signal the amplitude of the modulation and the number of modulation cycles per sequence Any pa
45. eld intensity that is make B equal a single component B z as we called it within much less than 1 ppm of By since the component of the field perpendicular to Bz that is B ER has the same order of magnitude as the inhomogeneity in Bz As an example let us consider an enormous inhomogeneity in the 1000 ppm range say Bi BY 10 Be the field intensity B measured by the NMR probe will differ from Bz by less than 1 ppm since Bi Be BR RK B 1 Be B E 2B2 ge B 1 5 10 Z Z METROLAB Instruments SA Geneva Switzerland 65 MFC 3045 User s Manual IT TRUNCATION OF THE EXPANSION An important question to answer concerns the actual upper limitations of the values of n and m in the expansion of B in the form 1 Indeed the actual summation on n cannot go to infinity but must be stopped at some maximum value N In the same way the actual summations on m have to be stopped at M n lt n Clearly these limitations N Min depend on the quality of the magnet since a sufficient number of coefficients must enter the expansion 1 in order to describe correctly the field within the experimental accuracy The number of measured values which must be at least equal to the number of unknown coefficients is closely related to the cost of the apparatus number of probes and to the time needed for the data acquisition process As a consequence the truncation of the expansion 1 must be carefully optimiz
46. ent Value can be changed in the EEPROM Advanced commands level 2 38 Geneva Switzerland METROLAB Instruments SA MFC 3045 User s Manual 8 4 DATA ACQUISITION MEASUREMENT Starts a measurement NCY cycles of the frequency modulation using the modulation parameters previously set The magnetic field value on each NMR point will be measured and stored x 1 to Number of point of the P A all individual NMR frequencies of the selected measurement point will be also stored x 0 or if no parameter no individual storage will be done Search over the full range of the Probe Array SRC is similar to the RUN command see above except that the MFC 3045 selects a value of modulation amplitude to cover the entire range of the Probe Array It also selects a fewer number of modulation cycles and low precision TVP 1 to shorten the measurement time The purpose of this command is to quickly find the magnetic field value at the price of lower precision than a regular measurement The parameter x has the same effect as with the RUN command see above Continuous measurement Start a measurement using the modulation parameters previously set The continuous measurement does not stop infinite modulation cycles and must be stopped using the command BRK A new set of field values is available after each cycle and must be read during the measurement Only the field value can be read No statistics are avai
47. er are now stored in the Main Unit EEPROM The parameter x of the command RSP is the decimal value of all the setting bits set to 1 EE eee eee Hardware Software Parity 1 lt 2 gt Sg 7 8 gt Baud Rate gt handshake handshake lt yes gt no bit s RTS CTS Xon Xoff length se mae ER 52 Decimal values e The values between lt gt represent the setting when the corresponding bit is set to 1 e The Hardware or Software handshake is enabled when the corresponding bit is set to 1 e Bits 6 and 7 are not applicable and have no meaning e Bits 8 to 10 are used for the Baud Rate as follow bit10 bit9 bit 8 Baud Rate 2400 4800 9600 lt Default value 19200 28800 38400 57600 115200 4 sch CH CH CO CH ch sch EH CH 100 d 1 d 1 d 1 d 1 Examples RSP 1828 will set the RS232 parameters to 115200bd Hardware Handshake Odd parity 1 stop bit and 7bits 1024 512 256 32 4 1828 RSP 513 will set the RS232 parameters to 9600bd No Handshake No parity 1 stop bit and 8 bits 512 1 513 This is the default value Geneva Switzerland METROLAB Instruments SA MFC 3045 User s Manual COTA TA OTTO ETT RSP RSP x RS232 parameters This command is used to change the 0 1855 529 RS232 settings see above ADV ADV x Advanced commands 0 not allowed 1 level 1 gt advanced commands allowed 2 level 2 gt like level 1 plus enable the modification of settings in no volati
48. er s Manual WMFCtool Main Menu Measures Data Display Configuratio Enter the password Low Level Calibration EEPROM FirmWare mode Utilities Update Calibration Probe Array a Main Unit Figure 18 Synoptic to access the Calibration menu in WMFCtool 26 Geneva Switzerland METROLAB Instruments SA MFC 3045 User s Manual 6 3 MAIN UNIT CALIBRATION 6 3 1 Necessary components The necessary components required to perform this calibration are the following e The MFC 3045 Main Unit to calibrate with its power supply e WMFCtool software V8 0 or higher installed into a PC station under Windows 95 or NT e A Frequency counter used as a standard instrument to calibrate the MFC 3045 local oscillator lt needs to measure 10MHz with a precision better than 0 1Hz 6 3 2 The calibration process This routine is used to get the local oscillator of the MFC 3045 Main Unit exactly calibrated and so obtain exact absolute values in field measurements For this reason it is necessary to let the L oscillator warm up for at least 10 minutes There is no other point to calibrate in the Main Unit For this calibration it is needed to have a frequency counter able to measure 10 MHz with an absolute precision better than 0 1 Hz lt 107 The calibration consists in generating a 10 MHz reference signal with the Main Unit by entering in the Calibration of Main Unit window Then the signal available on the RF Pro
49. es between probes are stored in a calibration table in the Probe Array s EEPROM A set of commands is available to facilitate the normalisation process Remember after any change of the EEPROM as well as after a normalisation process the change must be written permanently in the EEPROM using the command SPA Probe Array EEPROM or SMU Main Unit EEPROM otherwise modification will be lost if the MFC 3045 is reset or switched OFF SMU SMU gt EEP Settings of Main Unit With no parameter this command sends back to the PC the contents of the Main Unit EEPROM in one block of ASCII characters coded in hexadecimal with a check sum at the end It is always in one hexadecimal block whatever the setting of the command BLK If the parameter is after the comma the ASCII character gt EEP then the Main Unit EEPROM is written with the setting temporarily stored in RAM making any change permanent SPA SPA gt EEP Settings of Probe Array With no parameter this command sends back to the PC the contents of the Probe Array EEPROM in one block of ASCII characters coded in hexadecimal with a check sum at the end It is always in one hexadecimal block whatever the setting of the command BLK If the parameter is after the comma the ASCII character gt EEP then the Probe Array EEPROM is written with the setting temporarily stored in RAM making any change permanent Commands only available as Advanced commands level 1
50. eseccsseeesseeceseeeesaeecsscecscecesaeeesaeesseessneeeesaeeeeaeers 30 6 4 3 EE V erT CA UON aE n E TE E A ETE EEE NEEE EA E SO 31 7 MFG 3045 FIRMWARE UPDATE 33 8 MFC 3045 BASIC COMMANDS lt lt lt NENNEN NNN NNN nnmnnn 35 8 1 General conslderatons rr 35 832 Modulation parameters esos 36 8 3 Measurement Darameiers ENEE 38 8 4 Data Acquisition Measurement ooooococcccnnncconncononcnnncccnnnnnnnnnnnnnnnnnnnnnnnnnnnn cnn nnnnnnnnnrnnrrrnnnnnnnnnnnnncnnnnnns 39 RRE EE Le ee EE A0 8 5 1 After a RUN or a Search SRC a 40 8 5 2 During a continuous measurement CTNI nn ncnnnnnnns 41 8 6 Status and Ermore de dE ENEE tdi 43 801 STATUS TL A ais 43 8 6 2 STATUS 2 Modulation parameters erorgl cnn nc nnnnnnnnn nn nn nr nnnnnnnnnns 44 8 6 3 STATUS 3 Measurement status 8 6 4 STATUS 4 Miscellaneous status 8 6 5 STATUS 5 Baud Rate 8 COMMUNICATION eo 47 8 6 6 STATUS 6 COMMUNICATION seftmgsl cnn nn nn nnnnnn nn nn nn ncnnnnnnnn 48 8 6 7 Send Messages Automatically ocoonniconccininnninncooonncnncnnnnnnnnnnnnnncnnnnnnnnnn nn nn nc cnn nan nn cnn rr nnnnnnnnns 49 8 7 Probe Array sive nti ae i ada 51 8 8 RS232 settings and Miscellaneous commande 52 8 9 Probe Array Normalisation amp EEPROM ooococincccncninnccccccccncccnnnnn met 55 9 SPECIFICATIONS 0 a 59 921 Main WnitMFC 3045 wen acknowl Aah dE e aeS 59 9 2 Power Supply unit MEC 2048 59 9 3 Probe Array MEC 2048 59 9 4 Rotating Probe Arra
51. ference When a modulation parameter is changed X the reference is taken to calculate the other parameters xX Ref param Note MDA MCF MLF MHF Notes a MCF is the reference if MDA is changed b MDA is the reference if the present parameter is changed Modulation period The period of a frequency modulation cycle in P3 MDP MDP x ms If necessary the MFC 3045 will change the period to fit the 112 other modulation parameters Therefore the actual period can be different than the set or default value NSR e Number of steps for ramp modulation NSP rr Number of steps for plateau modulation DBR DDS Bit resolution returns the resolution of the RF steps during ramping up and down The resolution of a measurement is 1 decihertz dHz or given by the following formula which is the biggest 0 256e x 1 eH dHz where x is the value returned by DBR command H is the RF harmonic number used by the Probe Array 1 3 5 or 7 Commands only available as Advanced commands level 1 or more Gs Depends of the Probe Array Standard values can be different Value can be changed in the EEPROM Advanced commands level 2 gt a H gt METROLAB Instruments SA Geneva Switzerland 37 MFC 3045 User s Manual 8 3 MEASUREMENT PARAMETERS Number of measurement or modulation cycles 2 17500 y 80 Number of preliminary cycles Before any measurement 4 NPC x 1 the MFC 3045 performs du
52. g the Start button of the Remote Control box The redone measurement will replace the previous one in the file and in the display Put the switch back the Normal position to continue de sequence of measures Note that it is not possible to ReDo a measurement after the Measurement window is quitted using either the Exit Break button or any of the short cut buttons The multi measurement process can be aborted at any time by clicking the EXIT BREAK button The data already measured are saved in the file Important note about the Individual NMR point An individual probe of the array can be selected to get the history of all NMR signals on that probe Unlike in single mode individual data are not displayed in the results display and will not be saved in the file However after all the measurements are performed the individual data can be seen graphically in Data Display use the short cut button Data Display It is strongly recommended to put 0 zero in Individual NMR point field to avoid unnecessary data fill the memory and take time to be transferred Geneva Switzerland METROLAB Instruments SA MFC 3045 User s Manual Search It is similar to Single mode see above but the Search mode does not use the current measurement parameters Instead the Search mode uses parameters that cover the entire frequency range of the Probe Array This allows the user to find the magnetic field value if it is not well kn
53. hat the value or setting corresponds to the number of NMR probes in the Probe Array METROLAB Instruments SA Geneva Switzerland 35 MFC 3045 User s Manual 8 2 MODULATION PARAMETERS The NMR probes are excited with amplitude modulated Radio Frequency RF The shape of the modulation signal is given by a set of commands called Modulation parameters commands Some of these parameters are independent i e MDA MCF Some are semi independent meaning that the actual value can be different to fit the other parameters than the value set by the command i e MDP and some are dependant meaning that their values are calculated by the MFC 3045 and cannot be changed i e NSR Frequency Amplitude Frequency a gt eriod Figure 26 Shape of the Modulation Signal 36 Geneva Switzerland METROLAB Instruments SA MFC 3045 User s Manual Modulation amplitude Total amplitude peak to peak of the 200 Entire P A P A 1000 frequency modulation sent to the NMR probes in ppm of the Probe Array Central Frequency PCF Modulation Central Frequency This is the central frequency of the modulation signal In decihertz dHz 1 308 MHz MLF MLF x Modulation lowest frequency This is the frequency of the bottom 1 308 MHz plateau of the modulation signal In dHz MHF MHF x Modulation highest frequency This is the frequency of the top 1 308 MHz plateau of the modulation signal In dHz MRE MRE Modulation Re
54. he positioning guide already properly installed in the magnet and be sure the Modulation Parameters are correctly set see section 6 4 2 page 28 Click the button RUN REDO or press the Start button of the Remote Control box the magnetic field is then measured and its value stored for this probe Repeat this sequence positioning the Probe Array to the next position and activating measurement for the total number of probes of the array Normalisation of Probe Array Probes Measurements Process Probe stas Mess vale ua 4 Done 422996587 5 Done 422996411 EA AA RE le Probe Figure 22 Normalisation of the Probe Array window during the process On the Normalisation window the left column is the probe number presented with the sequence defined in Measurements order window The middle column indicates if the measurement is done and the right column is the magnetic field value The purpose of this last column is to quickly check the validity of the measurement i e a probe giving O indicates probably bad Modulation Parameters On the right hand side of the table an indicator shows the next probe to be measured The virtual LED has the same function as the Busy LED on the Remote Control Box it is red to indicate when the system is measuring Meaning that the Probe Array must not be moved At any time during the process it is possible to redo one of the precedent measures by selecting mouse click on it
55. ight factors WM In principle one should choose W 1 Max P cose but this would give rational numbers only for m n and would add a useless complexity to the expression In order to satisfy this latter condition one can take 64 Geneva Switzerland METROLAB Instruments SA wit n m 1 n m 1 where the double factorial notation has the following meaning 2p 2 4 6 2p 2Pp with Ol 1 2p 1 1 3 2p 1 with 1 1 Then all the WM PM cos which we shall use have their maximum absolute value in the range 5 1 Table I gives for these terms the angle in degrees at which they are maximum and the corresponding value of this maximum Table II gives explicitly the expression of the first term of the expansion in cartesian coordinates in order to recall the ancient labels of the shims z x y SN XZ Ke coined by the pioneers of NMR spectroscopy NB Another possible choice for the weight factor is wit n m n m which is part of the rationalization factor of the spherical harmonics This can be introduced on demand as an option Now the problem is to find a unique set of coefficients which is fully equivalent within the experimental accuracy to a three dimensional array of measured magnetic field B B B B but in the case of MRI magnets the uniformity of the field is always good enough to values The NMR teslameter measures the fi
56. il they are all read even if one or more modulation cycles have been performed during the data transfer The first value returned by the MFC 3045 is the modulation cycle number since the beginning of the continuous measurement Data transfer Block Mode 0 One by one mode The values are returned sequentially one by one Decimal block mode The data separated by lt CR gt lt LF gt are returned in one block of decimal values Hexadecimal block mode The data are returned in one block of hexadecimal values Each value is 4 or 8 characters There is no separator between each value Note BRK stops the transfer of data when in block mode Magnetic_ B field value The magnetic field value in decihertz dHz for each measurement point The values are returned according to the Data Reading Mode see section 8 5 1 above If no value is available lt CR gt lt LF gt are returned There are 8 hexadecimal characters for each value when in Hexadecimal Block Mode Standard deviation on each NMR frequencies measured one per modulation cycle for each measurement point In decihertz dHz The values are returned according to the Data Reading Mode see section 8 5 1 above If no value is available lt CR gt lt LF gt are returned There are 8 hexadecimal characters for each value when in Hexadecimal Block Mode BSD is not available in Continuous measurement CTN METROLAB Instruments SA Geneva Switzerland 41 MFC 30
57. ing no special care However the user must keep in mind that the presence of small magnetic parts mainly located in connectors can create a mechanical force if the main unit is put into the magnet This Main Unit contains all the electronic elements driving the Probe Array and managing measures e The RF source with the DDS circuit generating the high precision frequency modulated signal e Programmed integrated circuits that count the NMR frequency for each probe of the Probe Array e The bi directional communication transfers via the RS232 port to the PC e The management of the various operating modes of the measuring system METROLAB Instruments SA Geneva Switzerland 5 MFC 3045 User s Manual MA Ganeva Ce LD CAMERA MIC 3045 Figure 4 View of the Main Unit MFC 3045 The Main Unit MFC 3045 is dedicated to a type of Probe Array with respect to the maximum number of probes 32 64 or 96 that it can handle Otherwise it is universal with respect to central frequency and operating mode Thus the same unit may control any Probe Array under the condition that the number of probes is compatible with the MFC 3045 configuration By default the Main Unit has 32 channels one channel per probe The connectors of the MFC 3045 can be seen in the following figure Lemo 8p Size 3 Lemo 5p Size 1 Lemo 2p Size 2 Power Supply Remote Control box RF connector 25p Sub D connector Industrial 37p Sub D Closed door to th
58. ion error This bit is set to 1 when at least one of the bits of the status 2 is set to 1 bit 1 command error This bit is set to 1 to indicate that an error occurred with a command meaning that the syntax is wrong or that the parameter is outside the possible range or that the command is not applicable The last command which gave an error is returned by the command ERR bit 0 data ready This bit is set to 1 to indicate that the data are now available for reading METROLAB Instruments SA Geneva Switzerland 43 MFC 3045 User s Manual 8 6 2 STATUS 2 Modulation parameters errors The Status register 2 shows modulation error conditions When a condition occurs the corresponding bit is set to 1 The bits are cleared to 0 after reading the status register except the bit 7 command ST2 If one of the bits of Status 2 is set to 1 the bit 2 of Status 1 is set to 1 P A not Modul param Allowed lost Cycle lost Period not Max amplitude Period longer Period shorter connected exceed DDS __ cycle reached stable reached than setting than setting range bit 7 P A not connected This bit is set to 1 if the Probe Array is not connected or disconnected The MFC 3045 must be switched OFF before connecting a Probe Array bit 6 Modul param exceed DDS range This bit is set to 1 to indicate that a modulation parameter exceeds the frequency range of the DDS frequency generator bit 5 Allowed lost cycle reached This b
59. ires some time but must be done only once since this information can be stored for further use Steps 1 and 2 can also be used to control the static characteristics of the field generated by the pulsed gradient coils set The whole process is monitored by a small computer portable PC size and the software has been given a high degree of adaptability to various situations I BASIC PRINCIPLES It is known from Maxwell s equations that in a magnetically empty region of space that is a region without any electric current or any piece of magnetic material a stationary magnetic field obeys the two equations div B 0 curl B 0 In order terms this means that B is the gradient of a pseudo scalar potential V which is solution of Laplace s equation B gradV AV 0 62 Geneva Switzerland METROLAB Instruments SA MFC 3045 User s Manual It is thus possible to make a decomposition of V on the basis of a complete orthogonal set of functions which are solutions of Laplace s equation The choice of this particular set of functions is restricted by the fact that a magnetic potential like V cannot be uniquely defined in the whole space since the equation curl B 0is only valid in the magnetically empty regions of space In the actual situation it appears that the best choice is to use the spherical harmonics as the basis for an expansion of the spatial dependence of V and consequently of the field This expansion will be
60. it is set to 1 during a measurement to indicate that the allowed number of lost modulation cycle has been reached see below The measurement will be aborted if one more modulation cycle is lost bit 4 Cycle lost This bit is set to 1 during a measurement to indicate that one or more modulation cycles has been lost due to overtime in data processing It is of no consequence except that the measurement lasts longer The measurement is aborted if the maximum allowed lost cycle is reached bit 3 Period not stable This bit is set to 1 during a measurement to indicate that the period is not stable meaning that one or more modulation cycles have been delayed to allow enough time to process data during the plateau high bit 2 Max amplitude reached This bit is set to 1 to indicate that the modulation amplitude is too high The real value has been set to the maximum possible bit 1 Period longer than setting This bit is set to 1 to indicate that the period has been set to a higher value to fit the other modulation parameters This typically happens with high modulation amplitude values bit 0 Period shorter than setting This bit is set to 1 to indicate that the period has been set to a lower value to fit the maximum length of the plateau This typically happens when the modulation period is high and the modulation amplitude is small 44 Geneva Switzerland METROLAB Instruments SA MFC 3045 User s Manual 8 6 3 STATUS 3 Measu
61. ition on the guide and redo the measurement If the error is confirmed it is possible to modify the correction value of that probe in the editing box located on the upper left corner of the window labeled Correction value it is not possible to modify the value directly in the table Then redo again the measurement If remaining errors shows a global discrepancy then the whole normalisation of the Probe Array should be resumed after finding and canceling the possible external cause of this variation When clicking on the EXIT button or pressing the lt ESC gt key a dialog window pops up to enter the name of a file where the data will be saved If all the probes have been measured the possible modification of the correction values is saved into the Probe Array EEPROM as well as the normalisation date It is why it is very important to not switch off the Main Unit or disconnect the Probe Array before exiting the Verification window lf not all the probes have been measured the possible modifications of the correction values are discarded At any time it is possible to store the data in a file by clicking on SAVE ASCII FILE button Note It is not necessary to do a normalisation procedure before a verification But in that case the Target value will be set to 0 Thus the remaining error which is the difference between the actual magnetic field value measured by a given probe and the Target value expressed in ppm of the Target value
62. l magnet and of the shimming system as given by the manufacturer or guessed by the user The accuracy of this adjustment is not critical and even a few degrees of misalignment will not significantly spoil the shimming process The choice of the x and y directions is a pure question of convention but of course it must be consistent with that of the designer of the shimming system This question is discussed with more details in the documentation of the shimming packages Concerning the field measurement itself the teslameter multiplexes the probes and the measure is repeated at every position a sufficient number of times under the control of a simple statistical analysis in order to achieve the require accuracy 1 ppm These data are immediately fed to the computer which calculates the set of the N first coefficients of the decomposition according to table III with a chosen Ne lt No Ne can be changed and the decomposition restarted to analyze the stability of the process since for each decomposition the computer gives the mean square deviation between METROLAB Instruments SA Geneva Switzerland 67 MFC 3045 User s Manual the Np measured values and the calculated ones on the basis of the Nc coefficients together with the maximum local deviation and the particular point where it occurs The total time necessary to complete a whole field plotting and decomposition after having installed the system is only a few seconds
63. lable Hunt Mode This mode selects one of the NMR probe and uses it to track the magnetic field over the entire Probe Array frequency range The field value measured by the selected probe is available at any moment through the command BFV x selected NMR probe x 0 stops the Hunt Mode Breaks This command breaks any mode of data acquisition In this case no data is available This command also breaks the data transfer when it is done in block mode see BLK NP Number of NMR probes measurement points METROLAB Instruments SA Geneva Switzerland 39 MFC 3045 User s Manual 8 5 DATA READING The data are available at the end of a measurement made with RUN or SRC Status is set when the data are available The data are returned sequentially from NMR point 1 to n one There are several modes of data transfer The command BLK and the syntax of the reading data command determine the transfer mode In the following explanation the reading of the magnetic field value BFV is taken as an example 8 5 1 After a RUN or a Search SRC a Random access By adding a measurement point number as parameter of a data reading command the MFC 3045 will return the decimal value of the selected measurement point whatever the block mode selected with the command BLK Example DEN Where x is 1 to NP NP is the number of NMR probes of the Probe Array returns the magnetic field
64. le memory EEPROM ed Reset the system Equivalent to switch On VER Version l 012 VER x 0 or no parameter returns the MFC 3045 firmware version 43 characters 1 returns the Main Unit EEPROM version 5 char 2 returns the Probe Array EEPROM version 5 char SIN Serial Number 0 2 S N x 0 1 or no parameter returns the Main Unit serial number 17 characters 2 returns the Probe Array serial number 17 char Remote Box busy LED This command controls the busy LED LED x LED on the Remote Box 0 LED is OFF 1 LED is switched ON and OFF automatically with the RF 2 LED is switched ON immediately and switched OFF at end of the measurement 3 LED SON 4 LED is blinking slowly 5 LED is blinking quickly DDS fixed frequency an un modulated RF signal is DFF DFF x outputted by the frequency generator at the frequency given 0 44010 by the parameter x in decihertz dHz until DFF O or BRK is received by the MFC 3045 Commands only available as Advanced commands level 1 or more 1 Commands only available as Advanced commands level 2 Value can be changed in the EEPROM Advanced commands level 2 METROLAB Instruments SA Geneva Switzerland 53 MFC 3045 User s Manual el ware owcipien Cas TN FSW x Frequency Sweep This is a special command used to tune 0 44010 the Probe Array It allows the user to shift MCF by the value of x given in dHz during a contin
65. libration are the following e The Probe Array MFC 3048 to normalize defined by its number of probes and the RSV diameter in mm e The MFC 3045 Main Unit with its power supply e The Remote Control box e WMFCtool software V8 0 or higher installed into a PC station under Windows 95 or NT e A Positioning Guide corresponding exactly to the specification of the Probe Array The name of this guide defines its type as HMxx yyy where xx number of probes and yyy diameter mm e A solenoid superconductive magnet set to the nominal field value of the Probe Array 6 4 2 Physical installation of probe array After connecting the previous elements the main preparation consists in placing the positioning guide in the magnet so that the place labeled CENTER corresponding to the measuring site is in a homogenous region of the magnet approximately in the center of magnetic field A second precaution is to orient the positioning guide in such a way that the diameter of the Probe Array is parallel to the magnetic axis exactly the same way the Probe Array will be normally used Geneva Switzerland METROLAB Instruments SA L MFC 3045 User s Manual Then before starting the normalisation process it is strongly recommended to backup the content of the Probe Array EEPROM To do that go in the EEPROM Utilities window read the EEPROM and then save its content in a file See section 5 3 page 23 The Probe Array is put
66. longer than setting Period shorter than setting Status 3 Remote LED RF generator ON Hunt mode active Search active Continuous meas active Meas RUN active data avail Error with Main Unit EEPROM Error with P A Status 4 EEPROM EEPROM SUCCESS wrote changed state Remote button Remote button state Overflow in creating calib table Data in RAM lt gt EEPROM Hardware problem Ghost int Status 5 Reserved Framing error Parity error Overrun error Check Sum error RS232 Baud Rate Status 7 Probe Array Conditions not connected Remote Box button released Hardware handshake RTS CTS Remote Box button depressed handshake Software Xon Xoff Misc error EEPROM Odd Even parity Communi cation error Parity set Modulation error 1 2 stop bit s Command error 7 8 bit s length Data Ready Message sent PA UP DN CE SMA param value o o 64 32 16 2400 4800 9600 19200 28800 38400 57600 115200 Baud Rate 222x x0000 2 00 00 00 0 0 00 Hardware handshake RTS CTS Software handshake Xon Xoff Odd lt Even gt parity Parity lt yes gt no bit s 1 lt 2 gt stop 7 1 lt 8 gt bit s length al vk N D c Val gt
67. m used for shimming magnets at the customer s site 3 3 CONNECTIONS TO MAIN UNIT POWER SUPPLY AND PC The Main Unit MFC 3045 should be placed in a zone of magnetic field of less than 0 2T and then connected to its other external elements connectors are shown on Figure 5 such as e The MFC 3048 Probe Array via the LEMO 2p size 2 plug and the Sub D industrial connector e The Remote Box via the LEMO 5p size 1 plug e The PC via a 25p Sub D serial cable e The Power Supply MFC 3046 via the LEMO 8p size 3 plug These 2 last elements placed in the control room separated from magnetic field dangers should then be connected to the mains Before connection refer to the specifications of MFC 3046 Power Supply in section 9 2 page 59 90 to 264 AC Volts 50 60Hz and those of the PC in its own User s Manual 3 4 POWER SETTING It is recommended to switch on the PC before the MFC 3045 in order to get a good initialization of the system At the moment the system is in operation green LED indicators on the Power Supply case and on the Remote Box should be on if not verify the connections and the presence of line voltage on mains plug The red busy LED on the Remote Box must be On for less than about 2 seconds when the Power Supply is switched ON If it does not switch off it indicates a hardware failure in the MCF 3045 Main Unit Before using the MFC 3045 system for measurements wait at least a 10 minutes to allow the oven cont
68. mmy cycles allowing the NMR 0 100 PA 12 signal to stabilize This command reads writes the maximum number of preliminary cycles The real number of cycles is NPC or NPT see below divided by the period of modulation MDP which is greater Time duration of preliminary cycles This is the maximum P NPT x time duration in ms of the preliminary cycles This value 0 30 000 P A 600 divided by the modulation period MDP gives the number of preliminary cycles However the number of preliminary cycle is never less than defined by the command NPC see above A Rejection Signal Gap A measurement cycle is discarded ts RSG x from the statistics if the NMR signals of the ramps up and 111000 P A 40 down are not in the Gap given by this command In ppm of the Probe Array Central Frequency A Time versus Precision The time to do a measurement with TVP x high modulation amplitude can be decreased by a factor 2 011 to 4 However the measurement resolution will be lower by the same factor 0 Maximum precision longer time 1 Shorter time lower precision i Rejection Signal Offset This gives the offset between the RSO RSO x NMR signals of the ramps up and down In ppm of the 1 20 000 E Probe Array Central Frequency Commands only available as Advanced commands level 1 or more Commands only available as Advanced commands level 2 P A Depends of the Probe Array Standard values can be differ
69. nce value is far from the mean value see Probe Array Calibration chapter Reading the status clears this bit bit 1 Data in RAM lt gt EEPROM At power up the content of the Main Unit and Probe Array EEPROMs the configuration data are copied into the RAM system This bit is set to 1 to indicate that one or more configuration data stored in RAM has been changed using the Advanced mode level 2 and therefore the configuration data in RAM do not match the configuration data in EEPROM This bit is cleared to O when the EEPROM is successfully written with the new set of configuration data bit 0 Hardware problem This bit indicates that a hardware problem in the MFC 3045 Main Unit has been detected during startup Together with this bit the busy LED of the Remote Box is switched on permanently The instrument should be repaired 46 Geneva Switzerland METROLAB Instruments SA MFC 3045 User s Manual 8 6 5 STATUS 5 Baud Rate amp Communication error The Status register 5 is used to indicate the RS232 baud rate bit 0 to 2 and the communication error conditions bits 3 to 7 The bits 0 1 and 2 reflect the present condition while bits 3 to 7 are cleared when the status is read When one of the bits 3 to 7 is set to 1 the bit 3 of status 1 is set to 1 Ghost int Framing error Parity Overrun error Check Sum RS232 Baud Rate ee error error bit 7 Reserved This bit is reserved bit 6 Framing error This bit is set
70. normalisation of every Probe Array This normalisation consists of reducing the discrepancy between every probe of the array when placed in the same magnetic field The raw value of this discrepancy at the end of fabrication is approximately 2 ppm and can be reduced after normalisation to less than 0 5 ppm see section 6 4 page 28 8 Geneva Switzerland METROLAB Instruments SA MFC 3045 User s Manual Figure 9 Probe Holder MFC 3049 2 5 REMOTE CONTROL BOX The Remote Control box is a small plastic box connected to the Main Unit by a 4 meter length cable enabling it to be placed near the Probe Array holder It monitors the power on state of the MFC 3045 and allows to start a measurement as soon as the Probe Array has been moved During the measuring period an illuminated red LED indicates that the Probe Array cannot be moved to another angle If the LED is blinking it indicates that an error occurred in the system Power on LED Monitor LED Start button for measuring validation Reset pusbutton Figure 10 View of the Remote Control box and its commands METROLAB Instruments SA Geneva Switzerland 9 MFC 3045 User s Manual An additional push button actuated with a sharp tool such as the tip of a pencil or ball pen for security reasons allows a system reset The Remote Control box is also used to restore the default RS232 parameters The RS232 parameters are set by software only and they are permanently stored in
71. nstruments SA Geneva Switzerland 19 MFC 3045 User s Manual Data Display Graph of NMR Frequencies y 70 00 65 00 60 00 55 00 50 00 45 00 40 00 35 00 30 00 E 25 00 Es Graph legend box 20 00 15 00 10 00 5 00 1 a eres plato Prete es oa SANA AE AO 8 lle 3118 H ppm Iran MHz Base line MHz 21 1728765 Tool palette 12 13 96 02 11 08 gt Meas i D 12 13 96 02 11 1 1 Figure 15 Data Display window In graphic format a mouse click on the Graph legend box opens a pop up menu where color line and dot style can be changed for each curve The Tool palette can be used to zoom pan change the format of X or Y scale autoscale or change the units see details below The first measurement selected in the Measurement selector list is attributed to Plot 0 the second one to Plot 1 and so on Tool palette description You can choose the units of the Y scale The values are in MHz in Hz in the case of the ppm individual probe diff cycle or in ppm depending the position of the switch shown at the eng left The ppm are relative to a base line indicated below the graph The base line is calculated as the middle value between the highest and the lowest NMR frequency values is If you press the X Autoscale button shown at the top the graph autoscales the X axis If Ft you press the Y Autoscale button shown at the bottom the graph autoscales
72. number associated with the measurement number To edit the table click on a probe number that should be modified and enter a new probe number The RESET button allows to reset the entire table to its default setting Where the probes numbers correspond the sequence of measurement The CANCEL button or the lt ESC gt key will discard the modification and exit the window When clicking on the DONE button the measurements order is memorized and the normalisation as well as the verification will be done with that order The measurement order is saved with the other WMFCtool settings That means that when WMFCtool is started again the previous measurement order is restored However it s worth to check The buttons SAVE and LOAD are used respectively to save a measurements sequence in a file and to load in WMFCtool a previously saved measurement sequence Normalisation of Probe Array Choose Measurements Order Probe Number a E a of 4 e e Ser E Bl Bl Figure 21 Measurements Order window METROLAB Instruments SA Geneva Switzerland 29 MFC 3045 User s Manual 6 4 3 2 Normalisation of Probe Array During the normalisation process each probe of the array will be measured at the same position in the magnet The Normalisation of Probe Array window is showing a table with the sequence of probe defined in the Measurements Order window First place the MFC 3048 Probe Array on the first position of t
73. obes are mounted onto a Probe Array unit e The total measuring time is only a few seconds typically 5 seconds Since all probes are read simultaneously the total measuring time is greatly reduced e The Probe Array is dedicated to one field value and its range can be extended up to typically 12 e A Probe Array can be designed for any field value between 0 08 to 7 Tesla 3 4 to 300 MHZ e Generally the mapping of magnetic field is performed by measuring the points on the surface of a spherical volume This measurement is achieved by using a half moon Probe Array that rotates around the field axis This simple mechanical movement results in an excellent compromise between the price of the Probe Array time of measurement and the simplicity of the system Other geometries defined by the customer can be realized e The stability of the system is good enough to perform superconducting decay monitoring Version 3045D e The optional analysis software MFC 3050 gives the spherical harmonics coefficients of the measured field e The system is controlled by computer via an RS 232c interface e The system is supplied with Lab View software WMFCTOOL running under Windows NT or 95 WMFCTOOL allows to control store and view data With the MFC 3045 all measurements and data are expressed in dHz 1 10 of Hertz However for greater convenience the data in software WMFCTOOL are expressed in Hz or MHz with a resolution of the decihertz dHz
74. odified Measurement Parameters MLF L EE belle a TT Elek eil 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 Modulation Parameters Measurement Parameters Modulation Amplitude MDA ppm of PCF 1000 Number of modulation cycles NCY Modulation Highest Frequency MHF MHz 42 3211 Time Versus Precision TVP Modulation Central Frequency MCF MHz Modulation Lowest Frequency MLF MHz 42 2788 Probe Array Frequencies MHz Lowest Central Highest Modulation period MDP ms 50 l PETT l 23000 j l 431450 Reference Measurement time s 350 OW LEVEL FI F2 ES Figure 13 Measurement Parameters window 4 4 4 Measurements window This window is the heart of WMFCTOOL It provides the possibility of selecting different types of measurement Run Mode as well as starting the measurements and viewing the results Moreover the modulation parameters can be modified The aspect of this window varies according to the Run Mode selected The Figure 14 below shows the Measurements window in Mutt mode 4 4 4 1 Elements of the Measurement window common to all Run modes A The buttons Low Level Commands Parameters and Data Display are a short cut to the corresponding windows to avoid passing through the Main Menu Note that the Low Level Commands button is available only if the Advanced Options have been enabled in the Configuration window B Th
75. of a magnet The Search mode is a mode intended to find the exact field of a magnet in order to define the central frequency for the normal mode measurement In this mode the user cannot change the measurement parameters and they are automatically adjusted to cover the full range of the Probe Array The number of cycles is also pre defined typ 12 If the magnetic field value is somewhere in the Probe Array range then it will be measured The measurement parameters previously set during the normal measuring mode will be not changed by the Search mode Due to the low number of cycles and the large amplitude of the modulation typ 40 000 ppm the accuracy is not so high than in normal measuring mode but sufficient for setting the value of central frequency of the next measure in normal mode The Continuous mode is similar to the Normal Measuring mode and will use the same parameters with the exception that it runs continuously the number of cycles is not taken in account and has to be stopped by the user With WMFCTOOL a timer allows the user to stop automatically the Continuous mode This mode is intended to measure and survey the field value over a short period of time The data are available after each cycle and provided the Baud Rate is fast enough it is possible to obtain measurements at each cycle of the modulation typ 60ms The Hunt mode is used when establishing the current in a superconducting magnet It is a method of de
76. or by pressing the Start switch of the Remote Control Box During each run the Busy LED of the Remote Control Box is lit as well as the virtual LED in the Measurements window indicating that the Probe Array must not be moved METROLAB Instruments SA Geneva Switzerland 17 MFC 3045 User s Manual After a measurement run is performed the busy LED is off the results are displayed in the window and the Probe Array can be moved to next position The next measurement is indicated on the right hand side of the window It displays the next measurement number or the next angle to measure depending the position of the switch Numbers Angles located under the digits The interval between each angle can be set manually using the interval angle box or automatically if the Autom case is checked The automatic interval is calculated as 360 number of measurements This display can be hidden or not by clicking on the toggle button Meas Display Measurements Measurement File Normal M ReDo C Program Files wmfctoolsfield_map_1 dam 15 02 00 18 38 19 gt Meas 4 M 15 02 00 18 38 19 gt Meas 4 Measurement parameters 32 60 423000000 1000450 Mean value 42 2997268 Mhz 0 99350512 T max min val 42 2998269 42 2996256 17 46 diff max min 4 8 ppm of mean value NHR f MHz RMS Hz Valid cycles 42 2997269 2 42 2997069 3 42 2996869 2 Deg 42 2996669 2 42 2996469 7 Interval angle 7 7 42 2996256 Numbe
77. own The cost of the short time necessary for the Search is lower accuracy and resolution also some of the probes can give a O zero value The purpose of the Search mode is to find the magnetic field value thus the value given by any of the probes will be used to set the Modulation Parameters In order to do an accurate measurement using the Single or Mut mode The search should never be used for measurement Continuous This mode puts the MFC 3045 into a continuous measurement No data be will be acquired The continuous mode is only used for diagnostics and allows looking at the NMR signals with an oscilloscope After a click on the START button the Continuous Measurement window is opened A mouse click on the Run button of that window puts the system into continuous mode until a click on the Exit Break button of the Continuous Measurement window stops it A new click on the Exit Break button will quit the Continuous Measurement window Hunt This mode selects one of the NMR probes and uses it to track the magnetic field over the entire Probe Array frequency range The field value measured by the selected probe is available in the Hunt Mode window in Tesla or MHz unit A zero value indicates that the value of magnetic field is outside the Probe Array range or that the NMR signal is too weak due to the lack of field uniformity This mode is unfortunately not yet available 4 4 5 Data Display window Data Display is a
78. quences in the normal use of the equipment It also simplifies data reading e A Low Level mode which allows the use of any of the MFC 3045 individual commands for sending commands or retrieving data from the Main Unit In fact this mode is working like a terminal Any characters typed of the keyboard will be send to the MFC 3045 after the Enter key has been keyed and any characters sent be the MFC 3045 will be displayed on the screen This mode is useful for special operations and advanced commands but is rather long and boring to use for normal measurement purpose 10 Geneva Switzerland METROLAB Instruments SA MFC 3045 User s Manual 3 INSTALLATION 3 1 PROBE ARRAY The Probe Array should be first installed inside the magnet to be measured with the appropriate positioning tool for example the rotating Probe Array holder MFC 3049 with the Metrolab half moon type Probe Arrays in the zone to be mapped It should be then connected to the Main Unit MFC 3045 via the reinforced Sub D locking connector and to the LEMO 2pt size 2 RF connector 3 2 PC AND PRINTER The PC and attached printer are not delivered with the MFC 3045 system It must be IBM compatible running under Windows 95 or Windows NT system A Pentium processor or equivalent with 32MB of RAM is highly recommended Because the communication to the MFC 3045 system is achieved via the serial port a laptop PC is can be used This is especially true for a portable syste
79. rameters can be edited except the modulation period The modified parameter is validated by pressing the lt Enter gt key or by selecting another value When one of the modulation parameter is modified the others are calculated using the yellow highlighted parameter as the reference The reference parameter can be changed by selecting a different one in the field Reference The modulation frequencies values can have any value inside the range of the Main Unit frequency generator If one of modulation frequency falls outside the MFC 3045 frequency generator the modification is rejected and the previous value is restored If one of the modulation frequency parameters falls outside the Probe Array range it is displayed in red meaning that NMR signals will probably not be seen The total time in seconds needed for the measurement is indicated in the field Measurement time The Lowest Central and Highest frequencies of the Probe Array are also indicated METROLAB Instruments SA Geneva Switzerland 15 MFC 3045 User s Manual A button permits a direct access to the Measurements window The Low Level Commands button is available only if the Advanced Options has been enabled The graphic shows the shape of one cycle of the modulation The flat zones between rising and falling frequency ramps are used in the MFC 3045 to do mean and deviation calculations of the N channels corresponding to each probe of the array lts duration cannot be m
80. rement status The Status register 3 reflects the present state conditions Reading the status does not clear the bits ERA A Remote LED RF generator Hunt mode Search active Continuous Meas RUN data avail ON active meas active active bit 7 and 6 These 2 bits indicate the state of the LED on the Remote Box D bit6 0 0 LED is Off 0 1 LED is Lit 1 0 LED is blinking slowly 1 1 LED is blinking quickly bit 5 RF Generator ON This bit is set to 1 when the RF Generator in ON It is set to O when the RF Generator is switched OFF bit 4 Hunt mode active This bit is set to 1 to indicate that the Hunt Mode is active and it is cleared to O when the user stops the Hunt Mode bit 3 Search active This bit is set to 1 at the beginning of a Search and it is cleared to O at the end of the Search process bit 2 Continuous meas active This bit is set to 1 at the beginning of a Continuous measurement and it is cleared to 0 when the user stops the Continuous measurement bit 1 Meas RUN active This bit is set to 1 to indicate that a measurement RUN is in progress and it is cleared to 0 at the end of the measurement bit 0 data available This bit is set to 1 to indicate that data can now be read This bit is cleared to 0 at the start of a measurement METROLAB Instruments SA Geneva Switzerland 45 MFC 3045 User s Manual 8 6 4 STATUS 4 Miscellaneous status The Status register 4 reflects mis
81. rolled crystal of the reference oscillator to warm up in order to obtain full measurement stability 3 5 SOFTWARE SET UP Please refer to section 4 2 page 13 for the PC set up of the WMFCTOOL software METROLAB Instruments SA Geneva Switzerland 11 MFC 3045 User s Manual 12 Geneva Switzerland METROLAB Instruments SA MFC 3045 User s Manual 4 MFCTOOL FOR WINDOWS V8 0 4 1 GENERAL DESCRIPTION The MFCTOOL for Windows WFCTOOL package is a LabView based software that provides immediate access to the control and operation of the MFC 3045 measuring system Running under Windows 95 or Windows NT operating systems it allows the user to access all of the usual commands and instrument parameters and to achieve all the measuring sequences designed in the MFC 3045 Firmware This software also displays Measuring data files making immediately available the good or bad results of a measuring sequence This allows the user to immediately improve the measuring conditions for a new measuring sequence Finally this software contains Advanced functions like the Low Level Commands mode allowing the user to correspond directly with the MFC 3045 using its individual commands The calibration of the Main Unit and Probe Arrays as well as the possibility to update the MFC 3045 FirmWare are other Advanced functions 4 2 SETTING UP The PC installation of WMFCtool is done simply by inserting the WMFCtool CD ROM or diskette in the computer
82. rs ITLL Angles Autom 4 15 De 42 2997265 mi z s d E Current Modulation Parameters Run Mode Modulation Amplitude MDA ppm of PCF 1000 Mi W Meas displa Modulation Highest Frequency MHF MHz 42 3211 Individual NMR point 0 no storage 42 3000 0 Modulation Lowest Frequency MLF MHz 42 2788 Number of modulation cycles NCY 60 Number of measurements Interval m s 0 manual 24 0 0 Measurement time s Current Measurement Ready Meas 5 WE Lnmm Ez SS ME 3 WE emm Esc Figure 14 The Measurement window in Multi mode In the field Current Measurement a small comment can be edited before the run It will be saved in the headline of the data At any time during the process it is possible to display the results of one of the previous measurement Just select it in the blue pull down selector located on the upper right corner of the window When in manual mode Interval 0 it is possible to measure again redo any of the previous measurements even after the last run has been performed First put the switch located on the upper left corner of the window on ReDo position Then select the probe to redo using the pull down selector located under the switch Do not forget to put the Probe Array on the position corresponding to the probe that must be re measured redo Then run the measurement by clicking the button now labeled REDO or pressin
83. s in the first column the probe numbers in the sequence defined in the Measurements Order window The second column is the correction values for each probe displayed in decihertz dHz this is in fact the correction table stored in the Probe Array EEPROM after the normalisation process The third column indicates the corrected magnetic field value measured by each probe in MHz And the last column is the remaining error relative to the Target value expressed in ppm On the top right corner of the table there is a pull down selector to choose between the display of the table described above Numeric Results the graph of the correction values Graph CBT dHz or the graph of the residual errors Graph BFV Target ppm This last option leads to an immediate interpretation of the normalisation quality The display can be changed during the measurement process With the graphs the zoom and pan functions are available through the tool palette as explain in Data Display window refer to section 4 4 5 at page 20 On the right hand side of the table or graph an indicator shows the next probe to be measured The virtual LED located below this indicator has the same function as the Busy LED on the Remote Control Box it is red to indicate when the system is measuring Meaning that the Probe Array must not be moved Verification of Normalisation Correction value Target Value dHz 8 422997224 Numeric Results Correction
84. s the setting of the RS 232C communication parameters and different software preference METROLAB Instruments SA Geneva Switzerland 13 MFC 3045 User s Manual About Provides information about the serial and version numbers of the Probe Array the Main Unit and the software It can also be used to check the RS232 link Help Advanced This is a double function button By default this button Help opens a window that shows automatically the help available for the object pointed by the mouse i e button graph displays The Help window can be open at any time by L pressing the keys lt control gt and lt H gt simultaneously Ctrl H When the Advanced options box in the Configuration window is marked see section 4 4 2 page 14 this button is labeled Advanced and call the Advanced menu that gives access to the Low Level commands as well as other functions such as Calibration EEPROM utilities or FirmWare update menus The Advanced options are described in the Part B page 23 of this user s manual Remember that even if the button is labeled Advanced the help is always available by pressing CTRL H Quit Quit WMFCtool software Be careful the software doesn t prompt for a confirmation Almost all buttons have a short cut key It is a function key indicated in the lower left corner of the button Main Menu Key Navigation F4 Call the Configuration window to set the AS 232 settings the default directory and the
85. shold This gives a DC threshold level to 0 255 detect NMR signals Commands only available as Advanced commands level 2 PLF Probe Array Lowest Frequency in decihertz dHz Below 2010 308010 this frequency detection of NMR signals is not guaranteed P A Depends of the Probe Array Value can be changed in the EEPROM Advanced commands level 2 METROLAB Instruments SA Geneva Switzerland 51 MFC 3045 User s Manual 8 8 RS232 SETTINGS AND MISCELLANEOUS COMMANDS This section describes the RS232 settings as well as miscellaneous commands The RS232 settings or parameters can be changed with the command RSP x provided the Advanced mode level 2 is enabled When the MFC 3045 receives the command the new settings are applied Therefore the RS232 settings of the computer must be also changed accordingly Once the RS232 parameters have been changed the user can memorize them in the Main Unit EEPROM making the change permanent see command SMU It is always possible to retrieve the default RS232 settings 9600bd Xon Xoff disabled no hardware handshake 8bits no parity 1 stop bit Proceed as follows Press down the Button of the Remote Box then keeping the button down reset the MFC 3045 by pressing the reset button on the Remote Box or on the power supply or switching Off then On the system Keep the Remote Box button down until the LED is blinking quickly Then release the Button The default paramet
86. t be adjusted However each probe of the array measures the magnetic field with a small discrepancy due to the paramagnetic materials surrounding the probe The purpose of the Normalisation is to reduce the discrepancies to a few tens of ppm The normalisation of the Probe Array consists in placing each probe in the same homogenous and stable place of a Superconductive magnet in order to record the response in the magnetic field and after the last measurement calculate the mean value of these records Then a correcting value proportional to the difference between the individual response and the mean value is affected to each probe which allows to get rid of the small discrepancies between probe response The WMFCtool software V8 0 allows to perform completely the calibration and normalisation operations in a short time with user s friendly aid such as a record reminder or possibility of correction of an erratic point 6 2 USING WMFCTOOL FOR CALIBRATION First power on the MFC 3045 unit and allow 10 minutes warm up period to let the oscillator to stabilize completely Then start WMFCtool and follow the diagram below to reach the Calibration menu On the diagram gray boxes show the options to choose in each menu Please note that to access the Advanced menu the Advanced Options must be enabled in the Configuration window A password is required to enable the Advanced Options METROLAB Instruments SA Geneva Switzerland 25 MFC 3045 Us
87. tem to reject measurement drifts caused by noise or pulses present in the neighborhood of the system which are not representing the real field value At the end of each measuring cycle and for each probe n measures can have been found invalid The final NMR frequency measure is the mean value of the so defined N n valid measures At the same time the RMS standard deviation is calculated in terms of dHz in order to give an idea of the confidence level of the relevant measure The number of valid cycles N n is also recorded and displayed METROLAB Instruments SA Geneva Switzerland 3 MFC 3045 User s Manual 1 4 OPERATION MODES The 3045 system is designed to operate in measuring status in four main modes The normal Measuring mode used for magnet mapping and normal field measurements This mode consists of sweeping the frequency over a relatively small range within the 2 full range of the Probe Array in this mode the amplitude of the frequency sweep is typically 1 000ppm 0 1 of the nominal value of central frequency however larger amplitudes are allowed In this mode measurement parameters can be modified from default values using the joined software WMFCTOOL such as Central frequency Amplitude of frequency sweep Period of sweep Number of sweeps per measure This mode can be triggered from the Remote Box and allows to collect a set of measures which are able to define field homogeneity
88. termining when the field reaches the nominal value It monitors in real time the field value over the entire zone of sensitivity of the Probe Array typ 2 In Hunt mode when the field is external to the range sensitivity of the Probe Array WMFCTOOL displays 0 meaning that no NMR signal is detected When the field is within the range of the Probe Array a NMR signal is detected and measured The frequency is then displayed with a resolution of 1 kHz for example 63 275 MHz 4 Geneva Switzerland METROLAB Instruments SA MFC 3045 User s Manual 2 SYSTEM DESCRIPTION 2 1 GENERAL This system is intended to perform very reliable magnetic field mapping The various components of the system have been designed to yield an ergonomically optimized system for which the main electronic unit is completely blind no display no command and only the PC completed by an additional Remote Box allows all the necessary displays and commands PROBE HOLDER MFC 3049 PROBE ARRAY MFC 3048 3 meter 4 meter Figure 3 Physical representation of the MFC 3045 system 2 2 MAIN UNIT TYPE MFC 3045 The Main Unit is enclosed in an aluminum box with walls 6mm thick The box is then connected to the Probe Array by a 3 meter long cable It is designed to operate in magnetic surrounding of up to 0 2 Tesla and so can be located very near the magnet to be measured Its rugged construction makes it an element need
89. u release the mouse button lt Shift gt e clicking zooms in the other direction Note to zoom out quickly click on the X and Y autoscale buttons METROLAB Instruments SA Geneva Switzerland 21 MFC 3045 User s Manual 22 Geneva Switzerland METROLAB Instruments SA MFC 3045 User s Manual PART B Technical Topics 5 THE ADVANCED MENU If the Advanced options box in the Configuration window Advanced Menu see section 4 4 2 page 14 have been enabled the ADVANCED button is available on the Main Menu Clicking on it leads to the Advanced Menu shown at the left The Advanced functions are described hereafter Figure 16 The Advanced Menu 5 1 ADVANCED FUNCTION LOW LEVEL COMMANDS WINDOW This window allows a direct communication with the MFC 3045 Main Unit Any string of characters written in the Low Level Commands window will be sent to the MFC 3045 when the lt Enter gt key is pressed In addition all the characters send by the MFC 3045 will be displayed on the screen The purpose of the Low Level Commands window is to send basic commands to the MFC 3045 for test or diagnostics The basic set of MFC 3045 commands is described in chapter 8 page 35 5 2 ADVANCED FUNCTION CALIBRATION The Main Unit as well as the Probe Array need to be calibrated every 12 months The Calibration window will assist the user for the complete calibration process of both Main Unit and Probe Array The calibration process is describ
90. uous measurement CTN MCF is shifted up or down each time the PC sends the ASCII character 8 or 2 respectively No need of lt CR gt lt LF gt If x 1 the Probe Array range is automatically divided into 20 steps If x 1 the shift of MCF is limited to the Probe Array range A new FSW x will disable the limitation If x 0 the Frequency sweep mode is disabled ADV 0 will also disable the Frequency sweep mode Important to enable the shift by characters 8 or 2 the user must send any command or even only CR LF after FSW x 54 Geneva Switzerland METROLAB Instruments SA Update FirmWare This command allows entering into the Update FirmWare mode x must be 777067 This is the decimal ASCII code of ME C Any other value will generate a syntax error Once in the update mode the MFC 3045 works with a mini firmware stored in a special boot sector and therefore will accept only a few set of commands VER returns the firmware version VERY where x is any character returns the boot sector version ERA erase the firmware memory the MFC 3045 returns RR when it is erased Any string in the MOTOROLA S0 S9 format These strings content the FirmWare data The check sum is verified and the data programmed If the data programmed match the string and there is no check sum error the MFC 3045 returns RR If there is an error the MFC 3045 returns
91. valid at any point inside a magnetically empty sphere In such a spherical region of center O we take a cartesian coordinate system Oxyz with the z axis along the magnetic field vector Boat this point O Then the z component of the magnetic field has the unique form Se d n Aae 1 Y D IH P cose Y 1 cosmo J sinme W P cose 1 0 n 1 0 L m 1 5 The factors in bold characters Bg the intensity of the field at the chosen origin O Hn IT and Ji make up the unique set of coefficients of this particular type of B z expansion The coefficients H RK and JM which characterize the inhomogeneity of the field are dimensionless and can be given for instance in ppm The coefficients H will be referred to as axial since they are the only possible non zero coefficients in a situation of axial symmetry The coefficients Ty and JM on the contrary will be called non axial or off axis 6 The B and By components are given by other expressions which will not be written here They are governed by the same set of coefficients H M and JM only which means in particular that B and By are of the same order of magnitude as IBz Bol 7 r 0 0 are the usual spherical coordinates of a general point M in space gt gt E gt r OM 0z OM 0 lt 06 lt x and q Ox OH modulo 2x1 where H is the projection of M onto the xOy plane perpendicular to Oz METROLAB Instruments SA Geneva Switzerland
92. value for the probe x If the block mode is 0 BLK 0 this will also set the pointer to the next measurement point x 1 BFV 0 Has no effect with block mode 1 or 2 BLK 1 or BLK 2 It resets the sequential read pointer to the probe 1 if block mode 0 BLK 0 is used b One by one mode BLK 0 Each value is read one at a time After a reading command without parameter has been received by the MFC 3045 it returns one decimal value The reception of a new reading command will return the value of the next measurement point Thus the set of data will be read sequentially from measurement point 1 to the last one When all the values are read a new reading command will returns the ASCII character 17 CTRL W and the measurement point 1 will be selected again Example DEN returns the magnetic field value of one measurement point and point to the next one c Decimal block BLK 1 All values are returned in one block of data at the reception of a data reading command without parameter Each data is in decimal ASCII characters terminated by a lt CR gt lt LF gt leading 0 are not sent An ASCII character 17 CTRL W follows the last data value The data of the measurement point 1 is sent first then the other data follow in the order of the measuring point Example DEN returns the magnetic field values of all NMR probes in one block of data decimal values separated by lt CR gt lt LF gt d Hexadecimal block BLK 2 All values
93. venient shimming set the field correction cannot proceed by trial and error In most cases such a procedure would not converge to the best possible solution and in any case would be highly time consuming The method described hereafter does allow to find this best possible solution based on a rigorous mathematical analysis and to do it in a minimum of time since the proposed system does not use any moving part It proceeds in four steps METROLAB Instruments SA Geneva Switzerland 61 MFC 3045 User s Manual 1 Field plotting at the vertices of a three dimensional mesh in the region of interest by means of a NMR teslameter multiplexing a set of probes 2 Field decomposition or 3D transform i e data fitting with a general rigorous expression for the spatial variation of the magnetic field which leads to a unique set of coefficients describing the field in the region under consideration within a known accuracy 3 Calculation of the correction parameters which will give the best possible homogeneity with the considered shimming set and prediction of this homogeneity 4 Check of the result after activation or installation of the calculated shimming In some cases the effect of any of the various correction devices is not a priori known or is not given with a sufficient accuracy by the manufacturer By repeated application of steps 1 and 2 it is possible to collect the necessary information for entering step 3 Of course this requ
94. y each NMR signal of this individual probe are recorded and displayed at the end of the regular data This can be used to see a quick drift of the field for example A 0 zero value in Individual NMR point means that no individual probe is selected e Do not select an individual probe unless needed because it takes time to transfer the data especially if there are many modulation cycles Multi This mode is used to perform several measurements and save the data of each run in a specific file Its purpose is to map a magnetic field with a 2D Probe Array i e Half moon Probe Array or to measure the decay of the magnet In that case a timer triggers each run automatically The Multi mode is using the selected modulation parameters And it is possible to modify these settings between each run of the process In the field Number of measurements the user indicates the number of runs required If the field Interval is set to zero each run has to be triggered manually Otherwise the runs are triggered automatically when the time in min sec set in this field is elapsed When the START button is clicked with the mouse WMFCtool opens a window to select the name of the file where the data will be stored The name of the file will appear in the Measurement File indicator located in upper left corner of the window The default extension of the multi file is DAM Then the first run measurement is started by clicking the RUN button
95. y holder ME 2040 59 10 Appendix FIELD MAPPING seen 61 II Geneva Switzerland METROLAB Instruments SA MFC 3045 User s Manual PART A Using the MFC 3045 1 INTRODUCTION 1 1 GENERAL DESCRIPTION One of the major requirements for efficient Magnetic Resonance Imaging MRI is to have high enough magnetic field uniformity generated by the main magnet system The space homogeneity within few ppm is never obtained without using sophisticated correction systems shims The shimming process requires a precise measurement and analysis of the magnetic field that can be highly time consuming The METROLAB Magnetic Field Camera MFC 3045 system offers a very quick and easy way for mapping MRI magnets The speed of the MFC 3045 system offers inestimable advantage over all existing mapping and analysis systems The system is suitable for all mapping applications inhomogeneity analysis shim coil characterization gradient coil characterization superconducting magnet decay monitoring quality control etc The METROLAB Magnetic Field Camera MFC 3045 is a complete magnetic field mapping system for analysis of solenoid and dipole magnets The main features of the system are as following e The measurement of the magnetic field is based on NMR probes with a modulation of the radio frequency The field is measured with a relative precision better than 0 1 ppm The system handles up to 96 NMR probes that are all measured simultaneously The pr

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