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DSA2000-DSA2000A Digital Spectrum Analyzer User`s Manual

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1. File Edit Help Address L Type DSA 2000 1 ID Coarse gain 40 0 4 Gain Centroid Fine gain 1 6000 Gain Window S fine gain 0 015003 Gain Spacing Pole Zero 2048 Gain Ratio Coinc mode Zero Centroid 512 Offset fd Zero Window LLD Zero Spacing Zero Zero Ratio Conv Gain 8192 4 Gain Rate div ADC Range s192 Zero Rate div FDisc Mode Auto 1 Gain Corr rng ce a Fast Disc Zero Corr rng ce Inp Polarity Positive a Zero Mode Off Inh Polarity Positive Gain Mode off 5 Rise Time Preamp Type rca Flat Top PUR Hode BLR Mode PUR Guard Live Time Trim TRP Inhibit Figure 34 The VMS DSP Module Dialog Using the DSA 2000 with Genie VMS The values shown in the figure are typical defaults for a germanium detector with the exception of the address and the ID Leave the address field blank and enter 0 in the ID field the software will automatically retrieve the serial number of the device when the MCA configuration is created The HVPS Settings Next use the GUI editor to edit the HVPS parameters shown in Figure 35 Note that the DSA 2000 HVPS range and polarity settings allow only 5000 V 5000 V and 1300 V CAUTION Ti igh voltage Power Supply Module NIZOE1 CCNA lll File Edit Help
2. 8 8 1 2 or 16 8 2 4 Coaxial Germanium 2 8 0 6 or 5 6 0 8 Low Energy Germanium ee ae dl Performance Adjustments Refer to the specific Detector Operator s Manual for the recommended shaping time A good starting point is the Gaussian equivalent processing time selections listed in the table on page 87 The Rise Time and Flat Top setting can be optimized further through experimentation Collect spectra using rise time and flat top settings above and below the recommended settings to optimize resolution performance for your par ticular detector and application Flat Top Setting The DSA 2000 allows independent selection of rise time and flat top A detector with long charge collection times will require a flat top long enough to process all the charge from the detector see Automatic Ballistic Deficit Correction on page 64 If the flat top is too short it may result in low side spectral tailing and degraded resolu tion However if these symptoms occur at high rates only the P Z setting may be mis adjusted In this case first verify the correct P Z setting and readjust if necessary To set the flat top manually start with a long value then collect a spectrum and verify good resolution and peak symmetry Reduce the flat top and repeat the process Con tinue until resolution and peak symmetry begin to degrade then set the flat top to the next higher value The optimal shortest flat top will allow the best thr
3. Since MCA definitions are saved in disk files you can have as many definitions as you like For example you might have one MCA defined as an 1K Sodium Iodide Spec troscopy MCA in one file and another as a 2K Sodium Iodide Spectroscopy MCA in another file Before you start an experiment you simply pick the configuration you want to use Because an MCA definition file can include any or all of the MCAs that are available to your system you can use more than one MCA at a time However each MCA can be included only once in a given definition file and each MCA in that file must have a unique name Using the MCA Definition Files To use an MCA Definition you must first have saved the definition to disk as a file Once you ve done that all you have to do is load that file into the VDM s internal MCA Runtime Configuration Database From that point on all MCA operations will use the configuration information that was stored in the Definition File To change to a new configuration all you have to do is replace the database s contents with a new file Starting the MCA Input Definition MID Editor Starting the MCA Input Definition MID Editor Start the MID Editor by double clicking on its icon in the Genie 2000 Program Group The result will be the application window shown in Figure 9 MCA input Detinition Editor tocailinifitade r i Ple Database Edit vices ett wau Help ICA Input Size ADC MXR Figure 9 The MID Edito
4. 12 09 98 or higher Contact Customer Service for a firmware update if required To use a DSA 2000 input you must create a programmable module setup file specific to the MCA configuration The procedure is the same as that used for an AIM with computer controlled modules A sample setup file exists in the VMS ND_EXAMPLES directory called DEMO_DSP CCN 45 46 User Interface and Controls You must create one setup file for each port on the DSA 2000 that you want to use The device supports two input ports Port 1 is for PHA acquisition and port 2 for MCS acquisition Configuring the Device Settings To edit the setup file and specify the device settings use the Genie ESP Parameters Editor PARS GUD and to configure the DSA 2000 use the DSP Module the High Voltage Power Supply Module and the Miscellaneous Parameters The parameters in these modules are described in Defining an MCA starting on page 21 The DSP Module When you choose the DSP Module option yov Il see Figure 34 the DSP Module dialog DSP Module NIZ0E_1 CCN 1
5. Do not Initiate Auto BDC at this time Auto 2048 Available only on the DSA 2000A If equipped do not initiate Auto P Z at this time Please see Rise Time and Flat Top Adjustments on page 86 for additional information on setting the Rise Time and Flat Top settings and their relation ship to traditional Gaussian shaping times Tc Stabilizer Device Adjust Screen Gain Mode Zero Mode OFF OFF 57 Basic Spectroscopy Operation Detector Matching 58 The following section discusses how to adjust and optimize the pole zero can be set automatically for Model DSA 2000A and use the Auto BDC function Pole Zero compensation is extremely critical for achieving good performance at high count rates when using detectors with RC preamps It is equally important for good overload re covery due to high energy and cosmic events The Pole Zero adjustment range accom modates RC preamp fall times of 40 us to 1 7 ms When a reset type of preamp is used P Z compensation is not required and must be set to infinity represented by a value of 0 If you are using a detector with a Reset preamp such as the Canberra 2101 or 2008 use the MID Editor to change the preamp type from RC to TRP With TRP selected the Pole Zero compensation is automatically set to a value of 0 repre senting infinity or no compensation If the RC mode is selected the P Z SETTING must be set to 0 Please refer to Operation with Reset Preamps
6. Selecting ROI enables the ROI discrimination mode meaning that all incoming events processed by the DSP that fall within the selected discrimination window are counted ROI Start Sets the start channel of the discrimination window used when ROI mode is enabled ROI End Sets the end channel of the discrimination window used when ROI mode is enabled Note that the ROI Start End channels for the MCS input can be selected by setting up the DSA 2000 for Both inputs and using the PHA input to select the start end chan nels Using the DSA 2000 with Genie VMS High Voltage The High Voltage screen Figure 33 adjusts the High Voltage Power Supply HVPS Some of the controls shown in the figure may not be available on your DSA 2000 HVPS f MCS C Gain Filter Figure 33 The Adjust HVPS Dialog Note This window s initial focus is on the Cancel button pressing the keyboard s ENTER key after making changes in this dialog box will cancel the changes Be sure to click on the OK button to accept the changes Status This control allows you to turn the HVPS on off Voltage The Voltage scroll bar sets the output of the HVPS between the Voltage Limit s mini mum and maximum settings HVPS Reset This control resets any HVPS fault condition for example inhibit or overload Using the DSA 2000 with Genie VMS To use the DSA 2000 with Genie VMS be sure that the DSA 2000 s firmware is at revision 1 08
7. x 1 1 The PUR Guard adjust function is located on the Gain Device Adjust screen The value can be decremented incremented using the adjust slide bar The adjust range is 1 1x to 2 5x the default setting is 1 1x PUR Guard Adjustment Using a Live Spectrum As mentioned earlier detector preamplifier induced effects on the trailing edge of the shaped signal will cause spectral distortion low or high side tailing At moderate to high count rates observe the shape of the spectral peaks They should appear symmetrical Low or high side tailing may indicate the presence of preamplifier induced effects corrupting the trailing edge of the shaped signal This could also be due to a misadjusted pole zero Verify the Pole Zero is correctly opti mized refer to Detector Matching on page 58 or Appendix B Performance Adjust ments If the Pole Zero is not the problem set the PUR Guard to 2 5x and acquire a new spec trum If the symmetry of spectral peaks improves this affirms that trailing edge pileup effects associated with the shaped signal are responsible Reduce the PUR Guard time to the next lower setting of 2 3x and re acquire a spectrum If the symmetry and FWHM of the spectral peaks remain good reduce the PUR Guard time again to the next lower setting Repeat this procedure until spectral distortion begins to reappears then set the PUR Guard time to the next higher setting A Specifications Inputs AMP IN Accepts posi
8. DSA 2000 software package and is used by those programs to gain access to the actual MCA hardware in your system In this section we ll take a look at the procedures used for setting up that database Viewing the Current Database To view the current contents of the database click on the Database menu s View command which will pop up the display shown in Figure 26 If you click on a line in the list you can use the Device and Settings menus to look at details of that definition Click on OK to close the View window 36 Using MCA Definition Tables View Huntine pet Oehebon Database mput Sire ADC MXR Stab Amp WY Figure 26 Viewing the Database Loading and Unloading Definitions Before you can use an MCA Definition you ll have to load it into the database so we ll start with that process Note that you can t edit a loaded database you ll first have to unload it as described in Unloading the Database on page 38 The Load Unload functions will be disabled while any Acquisition and Analysis appli cations are running and have open datasources This prevents one user from altering the runtime database while another user is accessing it Loading the Database A new Definition can be loaded into the Database with the Load to command which brings up the Dialog Box in Figure 27 which lets you choose the file to be loaded into the database D GENIE2K MIDFILES Figure 27 The Load To Dialog 37 Use
9. The value 0 can only be set manually this setting is for no compensation which represents infinity required for Reset type preamps The Pole Zero value for successive Auto Pole Zero initiations may vary slightly This is normal and results from statistical variation associated with the algorithm and system baseline noise If Reset Mode was selected the four digit value will be set to 0 which is required for proper operation with reset type preamps Manual Fine Tuning Using the Pole Zero Slider Bar Detector Matching With the RC Pole Zero Mode selected the Pole Zero may be adjusted manually or the Pole Zero compensation value resulting from the automatic operation may be trimmed by adjusting the associated slider bar on the Filter Device Adjust screen This operation permanently overwrites the Auto value and may be used to fine tune the Pole Zero setting to optimize performance at high rates For additional discussion on manual Pole Zero adjustment refer to Manual Pole Zero Matching on page 61 Verifying Pole Zero Accuracy The precision of the Auto P Z operation can be verified by observing the reconstructed Trapezoid signal on the Monitor Output Observe the trailing edge of the Trapezoid signal as it returns to the baseline it should return with no over or undershoot Set the oscilloscope vertical range to an appropriate sensitivity Use a Canberra Schottky Clamp Box Model 1502 or equivalent to prevent oscillosco
10. address tyre osa m Oo Limit 2000 000 Y Overload latch enable Voltage 1000 000 Hi Inhibit latch enable Status MK Negative Output polarity 5v 12 inhibit Rely on module for ramp DSA 2000 HVPS Range Figure 35 The VMS High Voltage Dialog The HVPS settings are entirely software selectable there are no internal jumpers for selecting the HVPS range limit or setting It is very important that you select the appropri ate values for the detector to be used with the DSA 2000 Set these values in the CCN file before creating the MCA configuration in the steps that follow If in doubt disconnect the detector s HVPS cable before creating the MCA config uration for the first time The Miscellaneous Parameters Now set the Miscellaneous Parameters using the dialog shown in Figure 36 47 User Interface and Controls DSA 2000 Miscellaneous Parameters NI20E_1 CCN File Edit a eee Input 1 amp 2 l Negative Sample Changer polarity PHA Input 1 Y External start Y External stop HCS Input 2 Dwell Value Dwell Range l ps 2 ms 3 s Disc Mode ROI Start ROI End El External start Ol External stop o o o Cancel Figure 36 The VMS Miscellaneous Parameters Dialog Creating the MCA Configuration Once you have created the CCN file with the appropriate settings you can create an MCA configuration For example the following command will create an MC
11. and Pole Zero should be set prior to initiating the Auto BDC function Select the Filter Device Adjust screen under the MCA Adjust menu and press the AUTO BDC Start button The BDC BUSY LED will illuminate for the duration of the process During this time normal operation of the DSA 2000 is suspended while detector rise time data is being acquired Note Spectral data acquired during the Auto BDC process may be corrupted and should be discarded or cleared when the auto BDC Process has completed 65 Basic Spectroscopy Operation Upon completing a successful BDC and setting of the Trapezoid Flat Top the BDC BUSY LED will turn off Verify the new Flat Top setting The Filter Device screen must be updated to show the new value momentarily switch the Device Adjust screens by clicking on the Stab or Gain button then back to the Filter Device Adjust screen 3 Unsuccessful BDC and Error Messages If the Auto BDC operation fails to complete after initiation the BDC BUSY LED will turn off and the message General SAD error will be posted in the error dialog box Click on the Ok button to clear the message The BDC operation could have failed for one of the following reasons a BDC Time Out Error The Auto BDC has failed to complete within a maximum time of five minutes This may result if the de tector preamp signal is not connected or the incoming count rate ICR is below 1 kHz Additional causes may be excessive noise
12. click on the FILTER button then click on the Next button until the Adjust screen with the Auto P Z button appears Click the AUTO P Z Start button to start the Auto Pole Zero While the pole zero is converging Wait will be posted in the Adjust screen s Status box The pole zero value can be viewed on the Filter Device Adjust screen under Pole Zero or on the Status Page The pole zero value must be updated each time an Auto P Z is performed or when the slider bar is changed To update the pole zero value momentarily switch the Device Adjust screens by clicking on the Stab button or the Gain button then back to the Filter Device Adjust screen When a successful auto pole zero has been done the new pole zero value can be verified as indicated in step 3 above If the pole zero was unsuccessful an error message will be posted in the error dialog box Unsuccessful Pole Zero and Error Messages If the Auto Pole Zero operations fails to converge when initiated one of the following messages will be displayed in the error dialog box to provide diagnostic information regarding the problem The error message can be cleared by clicking on Ok in the error dialog box 59 60 Basic Spectroscopy Operation a Pole zero not possible with TRP You have attempted to initiate an Auto P Z operation with the Genie environment and hardware configured for a TRP detector that is a detector fitted with a reset type preamp The Auto P Z
13. counted from MCS IN connector Fast Discriminator Gamma events counted from DSP ROI Discrimination Gamma events counted if they occur within the programmed ROI window 81 Specifications Programmable Settings Dwell time TTL or Fast Discriminator 2 us to 2048 s Resolution 2 us to 204 8 us 100 ns 2 us to 2 048 us 1 us 1 ms to 2 048 s 1 ms 1 sto 2048 s 1s ROI Discrimination 4 us to 310 us Resolution 10 RT FLAT TOP us Sweep Counter 65 535 sweeps Disc Window 1 to 32768 channels Sweep Mode Sweep Counter or Sweep Forever MCS Channel Range 256 to 32 768 Start Control External Start via MCS S S Stop Control External Stop via MCS S S Preset Status bit available for sweep finished interrupt available for sweep count Performance 82 Signal Processing SPECTRUM BROADENING The FWHM of Co 1 33 MeV gamma peak for an in coming count rate of 2 kcps to 100 kcps will typically change less than 6 for 2 8 us rise fall time 0 6 us flat top and proper P Z matching These results may not be repro ducible if the associated detector exhibits an inordinate amount of long rise time sig nals INTEGRAL NONLINEARITY lt 0 025 of full scale over the top 99 5 of se lected range Performance DIFFERENTIAL NONLINEARITY 1 over the top 99 of the range including the effects from integral nonlinearity GAIN DRIFT lt 50 ppm C
14. for the charge collection time of the particular de tector Independent adjustment of the flat top allows the shaping function to be optimized for detectors with long charge collection time without a large increase in the overall processing time For small detectors with minimal charge collection time variation or ballistic deficit the trapezoidal shape reduces to triangular shaping when the Flat Top is set to minimum or zero The triangular trapezoidal shaping function is symmetrical The fall time cannot be set independently it always equals the Rise Time selection Shaping is adjusted by selecting the Rise Time and Flat Top which determine the Trapezoid pulse shape and optimizes performance for the specific detector spectral energy range and count rate As in any signal processing application a performance tradeoff exists between high resolution and high throughput For example when using a small Ge detector 5 6 us rise time and 0 8 us flat top settings provide optimum reso lution over a wide range of count rates However a 2 8 us rise time and 0 6 us flat top will degrade low count rate resolution performance slightly but results in less resolu tion broadening and peak shift over a much wider count rate range For ultra high counting and throughput rates rise time and flat top settings of less than 1 us may be used For this case optimum resolution is traded off for increased count rate performance For high resolution detectors longe
15. function is disabled when a TRP preamp is selected If you are using a detector with an RC preamp please go to the MID Editor and set the Preamp Type to RC b Pole zero failed to converge This message may result from any of the following reasons P Z Time Out Error The Auto P Z has failed to complete within a maximum time of two minutes The preamp fall time could be out side the 40 us to 1 7 ms pole zero adjustment range or the incoming count rate ICR is below 1 kHz The Auto Pole Zero will not con verge properly if the ICR is less than 1 kHz Additional causes may be excessive noise or abnormal variations of the Trapezoid baseline This could result from excessive detector microphonics high volt age arcing in the detector or preamp secondary preamp signal time constants or a damaged detector For those cases P Z compensation must be performed manually Please refer to Manual Pole Zero Matching on page 61 The Incoming Count Rate is Too High The incoming count rate ICR exceeds 20 kHz The Auto Pole Zero will not converge prop erly if the ICR exceeds 20 kHz For this condition the error mes sage will be posted very quickly long before the two minute time out Pole Zero Value The four digit value located under the pole zero slider bar is a reference number which varies from 0 to 4095 representing the pole zero adjustment range The values 1 to 4095 represents a time constant range of 1 7 ms to 40 us
16. nti Q Coinc rOffset LLD E Zero 0 16128 FDisc Mode Auto O Manual Figure 20 The DSP Gain Settings Inp Polarity Positive O Negative 9 Positive O Negative Apply to All The combination of Coarse and Fine Gain sets the overall system gain to match the re quirements of the detector and energy application overall gain is continuously vari able from x2 0 to x1536 The Fine Gain factor is dependent on the Super Fine Gain SFG value With the SFG set to 0 0000e the Fine Gain covers a range of x0 4 to x1 6 The SFG value adds to the Fine Gain factor and covers a range of 0 0000e to 3 0000e7 Coinc Mode Sets the devices gating mode ANTIcoincidence or COINCidence In COINCidence mode a positive GATE pulse de level or open input enables the conversion of the event in process in ANTIcoincidence mode a positive GATE pulse disables the con version of the event in process an open input enables conversion To enable disable an event the GATE pulse must occur during the trapezoid rise time and flat top The Trapezoid signal timing may be viewed on the MONITOR Output The GATE pulse duration must be equal to or greater than 50 nanoseconds This control can only be set via the MID editor Offset Sets the devices digital offset in channels The digital offset shifts the memory assign ment of the device s conversions to the left e g an offset value of 4096 would shift ch
17. of the DSA 2000 the slow channel is the digital filtered trapezoid signal Accurate Live Time Correction is obtained when the energy threshold and dynamic range of the fast channel and slow channel are the same In practice however the energy threshold of the fast channel is forced to be much higher compared to the slow channel In order to obtain good pulse pair or timing reso lution the fast channel employs little or no noise filtering As a result the signal to noise ratio is much worse requiring a higher energy noise threshold To optimize the LTC accuracy on traditional systems the ADC LLD is adjusted or op timized to normalize the energy threshold of the slow and fast channels However this has the undesirable effect of affecting the spectral low energy cutoff On the DSA 2000 the LT Trim function allows minor adjustment of the pulse evo lution time or dead time of the digital trapezoid signal to normalize the fast and slow channel energy thresholds without affecting the spectral low energy cutoff threshold 69 70 PUR LTC Operation The LT Trim has an adjustment value of 0 to 1000 and the default value is 250 which gives good Live Time correction performance for most applications In the steps that follow Live Time Correction accuracy is measured using the two source method which monitors the area of a reference spectral peak when subjected to varying rates of background counts Typical LTC performance referen
18. ohm terminators and additional BNC Tee connectors when required Tee Tee 50 ohm Connector Connector 50 ohm Terminator Terminator 10 Base 2 10 Base 2 DSA 2000 Host Computer Figure 4 Local Ethernet Connection Connecting to the Ethernet The DSA 2000 can be connected to other types of Ethernet networks using external transceiver units such as fiber optic or twisted pair The AUI connector on the rear panel of the DSA 2000 provides power and signal connections for these external mod ules At power on the DSA 2000 automatically senses the type of network connection and configures itself for Thinwire or AUI operation Note Note When using an Attachment Unit Interface AUI connector the external trans ceiver must have its heartbeat function enabled In IEEE 802 3 networks the heartbeat is a collision signal that is transmitted from the Medium Attachment Unit MAU to the Data Terminal Equipment DTE at the end of every packet Because communications on a Ethernet LAN relies on collision detection the heartbeat generator creates a pseudo collision to ensure that the collision circuitry is functioning correctly This pseudo collision consists of a 1 microsecond burst of 10 MHz oscillation at the line driver outputs approxi mately 1 microsecond after the end of the transmission This test is also re ferred to as the Signal Quality Error SQE test In most cases the heartbeat can be enabled or disabled via a switch or j
19. or abnormal variations of the Trapezoid baseline This could result from excessive detector microphonics high voltage arching in the detector or preamp secondary preamp signal time constants or a damaged detector For this case the Flat Top may be set manually select FLAT TOP under the Filter parameter group b Incoming Count Rate Too High The incoming count rate ICR exceeds 20 kHz The Auto BDC will not operate properly if the ICR exceeds 20 kHz For this condition the error message will be posted very quickly long before the time out occurs Acquiring a Spectrum 66 Please refer to the Genie 2000 Operations Manual for specific operating instructions Place a low activity Co source on the detector Set the MCA to COLLECT or ACQUIRE For the DSA 2000 setup performed in Spectroscopy System Setup on page 53 the 1332 keV Co peak should collect in channel 6500 to 7200 for a detector preamp gain of 500 mV MeV and 8192 memory or spectrum size Adjust the DSA 2000 s gain to position the Co peaks to the desired MCA spectral location The Super Fine Gain SFG control provides 100 times more resolution than the Fine Gain Use the SFG when matching the gains of several detectors or when es tablishing a specific gain calibration energy per channel 7 PUR LTC Operation The Model DSA 2000 Digital Spectrum Analyzer includes a pileup rejector and live time corrector The pile up rejector inspects for pulse pileup and allows on
20. or above the Centroid Hold disables zero stabilization but maintains the current correction adjustment at the Stabilizer s output Zero Ratio The Zero ratio value is interpreted by the stabilizer as the ratio to maintain between the two zero windows ratio upper window lower window For instance a value of 1 would be appropriate for a pure Gaussian peak Acquisition Window Adjust Screen DSP Gain Parameters The DSP Gain settings screen Figure 30 for the DSA 2000 contains the following controls Y Adjust C Stab CoHWPS _ C MCS earn C Filter Coarse gain Fine gain S fine gain PUR Guard Next 4960 y 1 6000 0 015004 1 10 KN O A LJ Be 7 600 0 0 03 11 25 _ Help Figure 30 The Adjust DSP Gain Dialog Coarse Gain Sets the device s coarse gain It s best to choose the highest Fine Gain which com bined with the Coarse and Super Fine Gains will produce the total desired gain Fine Gain Sets the device s Fine Gain multiplier S Fine Gain Sets the device s Super Fine Gain multiplier The combination of Coarse and Fine Gain sets the overall system gain to match the re quirements of the detector and energy application overall gain is continuously vari able from x2 0 to x1 536 The Fine Gain factor is dependent on the Super Fine Gain SFG value With the SFG set to 0 0000e the Fine Gain covers a range of x0 4 to x1 6 The SFG value adds to the Fine Gain factor and covers a range of 0 0000e
21. pile up rejection interval are increased The maximum Guard Time setting 2 5x requires the previous event to fully return to the baseline before subsequent events are accepted The default Guard Time 1 1x is minimum and provides opti mum performance and maximum throughput for most detector applications For the example shown above the second event begins before the first returns to the baseline This is not normally a problem and the second event should be accepted for maximum throughput However if the tail of the first event exhibited detector induced anomalies the second event would be corrupted and should not be accepted To pre vent acceptance of this corrupted event the PUR Guard should be increased as shown Some detectors with RC preamps may exhibit secondary time constants which is evi denced by a short lived undershoot or ring on the trailing edge of the shaped signal see Figure 46 PUR Guard This behavior is usually due to non ideal characteristics of the preamp feedback resis tor Events that fall on the tail of an event which exhibits this behavior will become corrupted or distorted when minimal guard time is selected In this case the spectral Scope Horiz 20 mV div Vert 10 us div Figure 46 Preamplifier Secondary Time Constant peaks will be distorted with excessive high or low side tailing at high count rates Events that arrive too close and are corrupted by the tail of the previous pulse can be rejected
22. selection it may be necessary to change the fuse as well Refer to Fusing on page 98 for information on fuse selection and installation 97 Voltage Selection 4 Voltage selection wheel Right Fuse holder extracted Cover Figure 52 The Line Entry Module Fusing 1 If not already done open the Power Entry Module s cover as described in Changing the Voltage Selection on page 97 2 Pull the left and right Fuse Holders from the Power Entry Module Replace the fuses in each of the holders with fuses of the correct the voltage and current rating Fuse selection information is listed in the Fuse Types section below 3 Reinstall the fuse holders into the Power Entry Module The arrows should point to the right as indicated on the inside of the Module s cover Fuse Types Note that two metric fuses are required IEC 127 Type T sheet 3 98 Replacing the Cover For 90 129 volt ac operation use two 4 A 5 mm x 20 mm fast acting fuses For 193 259 volt ac operation use two 2 A 5 mm x 20 mm slow blow low break fuses Replacing the Cover When you have finished changing the Selection Wheel and the fuses close the mod ule s cover and press on it until it snaps into the locked position 99 D Rack Mount Hardware A rack mount kit which includes one set of rack mount ears and hardware is shipped with the DSA 2000 Using 10 x 3 8 flat head screws attach the mounting brackets as show
23. the network with the ethernet interface set for 10base2 Thinnet and 10baseT AUD OK indicates that proper echo of the packet has been received and the Type reflects the interface detected FAIL in dicates that echo has not been received in either mode and the interface has been defaulted to Thinnet type ICB Comm OK The instrument s processor performs extensive read write operations over the internal ICB bus OK indicates no problems detected FAIL indicates failure in the ICB logic including unplugged or defective interconnection ICB cable If this test does not succeed then the DSP Init and DSP Version steps will not be performed DSP Init OK The instrument s processor directs the DSP processor to perform extensive ini tialization of the digital signal processing electronics using the DSPs battery backed parameters OK indicates the entire initialization sequence was success ful FAIL indicates failure in the ICB logic front end electronics or DSP sec tion The DSP CPU program versions are displayed DSP Versions Boot VO1 04 Main VO1 12 Front Panel OK The instrument s processor runs through a front panel initialization sequence by first setting each LED on then sequencing all segments of the graph LEDs on then sequencing to off then turn each LED off Small delays are added between each operation for viewing results A longer delay is added when the graph LEDs are at mid scale CO
24. 0 base 2 BNC connector on the DSA 2000 s rear panel 4 Make note of the four character label example 07C6 next to the Ethernet port This is the unique Ethernet station address for this DSA 2000 You will need to refer to it when you configure the instrument Connecting to the Host Computer 1 To the other end of the coax cable you just installed at the DSA 2000 attach a another BNC Tee connector and 50 ohm terminator 2 Attach the BNC Tee connector with coax cable and terminator attached to the female BNC connector on the Ethernet adapter card in the host computer The DSA 2000 and host computer are now ready for direct communication Power On When power is first applied to the DSA 2000 it will go through an initialization and self diagnostics process During this initialization period indicated by the Power On LED blinking the DSA 2000 is running internal diagnostic routines to verify correct operation of the hardware These routines require 15 to 20 seconds to complete The front panel hardware is tested next with the front panel LEDs and bar graph displays turning on sequentially for approximately 2 to 5 seconds As the bar graph displays se quence they will pause briefly at half scale The ICR LED may remain illuminated throughout the diagnostic check if an input signal is connected to the DSA 2000 s AMP IN connector If the diagnostics were successful and communication with the host computer is estab lished the P
25. 00 and 5000 This control limits the maximum voltage for the selected HV range preventing accidental application of excessive voltage to the detector Set the slider to the desired limit or maximum for the selected voltage range Sets the target high voltage value it is adjustable from 0 to the maximum voltage selected by the Range control Set the slider to the voltage setting required for the intended detector Sets the pull up voltage of the HV INH connector to 5 V or 12 V All Canberra detectors and preamps use the 5 V setting There are many other parameters that can be adjusted in the MID Editor but it isn t necessary to adjust them now They will be adjusted using the MCA Adjust Screens in the following step When you make adjustments be sure to save the MID File 7 MCA Adjust Screens The following parameters can be accessed and set using the Gain and Filter Device Adjust screens The adjustments can be saved to the datasource s CAM file by using the File Save command Ta Gain Device Adjust Screen Coarse Gain Fine Gain S Fine Gain FDisc Mode FDisc Setting 56 x15 x1 0002 0 0000 Auto 1 0 Spectroscopy System Setup LT TRIM LTC Mode PUR Guard Offset LLD Zero Conv Gain Inhibit Mode 250 On 1 1x 0 Ch 0 101 0 000 8192 Reset 7b Filter Device Adjust Screen Rise Time Flat Top Auto BDC BLR Mode Pole Zero Auto P Z Note 5 6 Us 0 8 Us
26. A config uration DET1 on port one of DSA 2000 NIACB2 S MCA CREATE DET1 N ACB2 1 CHAN 8K To create an MCA configuration DET2 on port two of DSA 2000 NIACB2 you might type S MCA CREATE DET2 N ACB2 2 CHAN 8K MODE MCS 48 5 Using the Monitor Output The Monitor Output is provided as a visual aid to assist with parameter setup and ver ify operation of the Model DSA 2000 Digital Spectrum Analyzer The Monitor Output uses a Digital to Analog Converter DAC to convert or reconstruct the sampled digital filtered signal with trapezoidal weighting function into the analog time domain for viewing The Monitor Output has 12 bits of resolution and an 8 volts dynamic range which re flects full scale for the selected MCA Conversion Gain It is only intended to drive the input of an oscilloscope for viewing as it has limited drive capability Using the Moni tor Output to drive accessories other than an oscilloscope such as traditional ADCs Mixer Routers etc is not recommended In addition to the reconstructed Trapezoid signal a small amount of digital noise may also be observed mixed in with the signal This is an artifact of residual noise pickup associated with the monitor output reconstruction DAC and associated circuitry and is normal The digital filter data being processed does not contain this noise Trapezoid Output The reconstituted trapezoid waveform provided on the monitor output is simil
27. MAIN MENU MODE Command Monitor On Command Monitor Off Erase Local Terminal Ethernet Monitor Diagnostic Monitor Diagnostic Menu DSA2000 DIAGNOSTICS Version 7 A Test SRAM F Help B Test Flash G Send ICB C Test Acquisition H Receive ICB SRAM D Test Timers I Test SNIC E Show Ethernet J Test DMA Address Diagnostic Option KEYS CTRL N CTRL CTRL E CTRL L CTRL D Ethernet Mirror Test Ethernet TDR Test Test ADC Test ICB Quit Diagnostic Mode Refer to the AIM556A documentation for description of these menus 107 F Installation Considerations This unit complies with all applicable European Union requirements Compliance testing was performed with application configurations commonly used for this module i e a CE compliant NIM Bin and Power Supply with additional CE com pliant application specific NIM were racked in a floor cabinet to support the module under test During the design and assembly of the module reasonable precautions were taken by the manufacturer to minimize the effects of ROI and EMI on the system However care should be taken to maintain full compliance These considerations include e A rack or tabletop enclosure fully closed on all sides with rear door access e Single point external cable access e Blank panels to cover open front panel Bin area e Compliant grounding a
28. MTEST OK Boot init OK 101 Using The Diagnostic Port CI DSA 2000 Main Master Program Versions ain VO0 95 Boot V00 07 Module initialization Leds init OK SNIC anit OK Timers init OK Buffers init OK Adc init OK Acq memory OK DMA Channel OK Ethernet Adrs 00 00 AF 00 AC B1 Ethernet OK TYPE ss Thinnet ICB Comm OK DSP Init OK DSP Versions Boot V01 04 Main VO1 12 Front Panel OK COP Timer enabled SNIC Buffer OK AVE TINTE OK Chngr Init OK READY Press Q for Main Menu Ctrl D for Diag Menu The DSA2000 s Initialization Sequence Each processor in the DSA 2000 contains two distinct programs a Program Loader also referred as the Bootstrap Boot for short and the Main Program which is also referred to as the Application Program The Bootstrap is used primarily for loading the Application program into the instrument 102 Initialization When power is first applied to the instrument control is immediately passed to the Bootstrap program which performs a basic memory test and critical initialization as re quired for basic operation Assuming the instrument is working properly the following text is sent at 9600 baud to the diagnostic terminal CI DSA 2000 Loader RAMTEST OK Boot init OK At this point the Bootstrap enters pause of about 10 to 15 seconds during which 1t exp
29. Model DSA 2000 A Digital Spectrum Analyzer User s Manual 9231280H 4 00 ISO 9001 SYSTEM CERTIFIED Copyright 2000 Packard BioScience Company All rights reserved The material in this manual including all information pictures graphics and text is the property of Packard BioScience Com pany and is protected by U S copyright laws and international copyright conventions No material in this manual may be repro duced published translated distributed or displayed by any means without written permission from Canberra Industries a division of Packard BioScience Company Canberra Industries 800 Research Parkway Meriden CT 06450 Tel 203 238 2351 FAX 203 235 1347 http www canberra com The information in this manual describes the product as accu rately as possible but is subject to change without notice Printed in the United States of America Table of Contents 1 Introduction ey cit ge Se ee ee HS RS ta BE eee We ee d 2 Controls and ComnectorS 2224 Front Panels lea uo a a Be de ale as ee a en aa asa Te Ga el a 4 Rear Panel as Aita amp Beech a Bred Btn ae Ba hd eee ee ease Ee ot 6 Internal Controls zess A Bee eld Mode hod AO we ho eh ets 7 3 Setup and Configuration 8 Unpacking the DSA 2000 Digital Spectrum Analyzer o o 8 Initial Setups lt a rs aa Se ea e Sune Sot as 9 Connecting to the Ethernet 2 2 ee 9 Power Onion e a
30. P Timer enabled The COP timer is also referred to as the Watchdog timer Its function is to de tect excessive program inactivity at which time it will issue a hardware reset to restart the instrument This feature is always enabled SNIC Buffer OK 105 106 Using The Diagnostic Port The instrument s processor performs write read write operation to the SNIC processors local memory OK indicates the w r w verification passed FAIL in dicates interprocessor communication failures NOTE that this test may indicate FAIL if host commands received by the module over the ethernet connection If in doubt disconnect the ethernet cable and repeat the test by cycling power to the instrument Note that doing so will cause the Ethernet test above to fail HV Init OK The instrument s processor performs initialization to the High Voltage hard ware OK indicates no failure FAIL indicates failure in the high voltage logic or disconnected signal cable Chngr Init OK The instrument s processor performs initialization to the sample change elec tronics OK indicates no failure detected FAIL indicates the S C logic failed to respond which typically would indicate failure within FPGA logic READY Press Q for Main Menu Ctrl D for Diag Menu At this point the instrument is running in its normal mode Pressing Q or Con trol D will display the appropriate menu Initialization Main Menu DSA2000
31. TO1 Input Size channels Detector Type Ge 4096 O Out of Service O Memory groups 1 i L 256 4096 Figure 23 The Define Input Dialog 32 Saving the Input Definition Note This window s initial focus is on the Cancel button pressing the keyboard s ENTER key after making changes in this dialog box will cancel the changes Be sure to click on the OK key to accept the changes Input Name The default DETnn name is the name displayed here allowing you to easily change it to a more meaningful name such as H20Sampl up to a total of eight characters Detector Type Use this drop down list to select the type of detector to be used with this MCA this also assigns appropriate default values to the spectrum display and analysis parame ters Input Size This parameter defaults to 8K the number of channels assigned during Device setup for the MCA on the assumption that you ll be using Full Memory for your data ac quisition To use less than the maximum available memory size use this control to se lect the size you want to use For instance for Nal spectra you wouldn t want to use more than 1024 channels Out of Service This Check Box allows you to place this Input temporarily out of service That is it will remain as an entry in your MCA Definition File but will not be available for data acquisition It is meant to be used when the MCA or its front end electronics are tem porarily discon
32. Top Sets the flat top portion of the digital filter time response The flat top matches the fil ter to the detector charge collection characteristics to minimize the effects of ballistic deficit The flat top time can be selected from 21 flat top selections ranging from 0 to 3 us Pole Zero Sets the device s pole zero setting 0 to 4095 The values 1 to 4095 represent 1 7 ms to 40 us a value of zero sets the pole zero compensation off infinity Auto P Z DSA 2000A only Available only for the DSA 2000A with the automatic pole zero option installed Initi ates automatic p z process at the device Auto BDC Initiates the automatic BDC process optimizing of the trapezoidal flat top parameters to match the collection time of the detector at the device 43 44 User Interface and Controls MCS Parameters The MCS settings screen Figure 32 for the DSA 2000 contains the following con trols C HyPS MCS C Gain Filter Figure 32 The Adjust MCS Dialog Dwell Range Sets the units for dwell time value Dwell Value Sets the dwell time value in units specified by the Dwell Range control Disc Mode The Disc Mode control establishes the MCS mode to be used Selecting FDisc enables the MCS s fast discriminator mode all incoming events processed by the DSP are counted Selecting TTL enables the MCS s TTL mode causes all TTL events as seen at the MCS IN rear panel connector to be counted
33. Voltage Power Supply HVPS LOW RANGE 5 V to 1300 V at 500 uA programmable to one part in 4096 cur rent limit 1 1 mA maximum HIGH RANGE 1300 V to 5000 V or 10 V to 5000 V programmable to one part in 4096 load current 100 WA from 65 V to 5000 V derated 1 3 WA per volt below 65 V current Limit 250 uA RIPPLE AND NOISE lt 5 mV peak to peak at full load for 1 3 kV range lt 25 mV peak to peak at full load for 5 kV range TEMP COEFFICIENT lt 50 ppm C after 30 minute warmup OUTPUT STABILITY Long term drift of output voltage is lt 0 01 h and lt 0 02 8 h at constant load and ambient temperature after 30 minute warmup VOLTAGE ACCURACY 10 of setting REGULATION For the 5 kV range lt 0 02 variation in output voltage over the load range at constant ambient temperature OVERLOAD PROTECTION The high voltage power supply will withstand any overload including a short circuit for an indefinite period Environmental OPERATING TEMPERATURE RANGE 0 to 50 C HUMIDITY Up to 80 non condensing OVERVOLTAGE CATEGORY II 84 Power Tested to the environmental conditions specified by EN 61010 Installation Category I Pollution Degree 2 Power 90 259 V ac 47 63 Hz in four user selectable ranges 90 113 V 103 129 V 193 243 V or 220 259 V selected by line entry module voltage selection wheel 60 watts maximum Line connector Line Entry module with integral IEC 320 connector t
34. ZERO DRIFT lt 10 ppm C OVERLOAD RECOVERY Recovers to within 1 of full scale output from x1000 over load in 2 5 non overlapped pulse widths at full gain at any shaping processing time and with pole zero properly set Pileup Rejector Live Time Corrector PULSE PAIR RESOLUTION 500 ns FAST DISCRIMINATOR Threshold set automatically or manually minimum de tectable signal limited by the detector preamplifier noise characteristics DEAD TIME CORRECTION Extended Live Time correction accuracy of reference peak area changes 5 3 typical up to 50 system dead time for 4 us Gaussian equivalent processing time Acquisition DATA MEMORY GROUPS 1 32K PHA channels single mode only 32 bits per channel three day data retention when power is lost Divisible into halves quarters eighths and sixteenths 1 32K MCS channels 32 bits per channel three day data re tention when power is lost Note During simultaneous operation PHA MCS PHA memory groups reside in lower 32K x 32 of acquisition memory i e PHA at 0 32K MCS at 32K 64K STORAGE MODE PHA Port 1 MCS Port 2 PRESET MODE ROI Live or True Time Counts per channel TIME RESOLUTION 0 01 s PRESET TIME 1 to gt 4 x10 s 83 Specifications Start Stop Sample Changer Support external PHA or MCS start stop and sample changer control RDY and ADVANCE simultaneously Programming of RDY and ADVANCE polarity are supported via computer High
35. annel 4096 down to correspond to channel zero of the memory 29 User Interface and Controls LLD Sets the devices Lower Level Discriminator LLD as a percentage of the ADC s full scale Zero Sets the device s zero intercept as a percentage of the device s full scale Conv Gain Sets the device s conversion gain It can be set from 256 to the maximum number of channels supported by the device The gain will change by a factor of two Note that this value is automatically copied down to the DSA 2000 s internal Conversion Range parameter FDisc Mode Sets the device s Fast Discriminator threshold mode AUTO allows the threshold to be optimized automatically above the system noise level MANUAL allows the threshold to be manually adjusted FDisc Setting Sets the device s Fast Discriminator threshold level when MANUAL Fdisc Mode is selected The range is 0 to 100 Inp Polarity Sets the device s Input signal polarity to either Positive or Negative The device s in put polarity must match the preamplifier s output polarity This control can only be set via the MID Editor Inh Polarity Sets the device s Inhibit signal polarity to either Positive or Negative If you are using a TRP preamplifier the Inhibit Polarity control matches the polarity of the device s In hibit reset input to the polarity of the preamp s Inhibit output This control can only be set via the MID Editor DSP Filter Set
36. ar to the output of a traditional spectroscopy amplifier when verifying operation and setup Fig ure 37 shows a typical trapezoidal waveform as viewed on the Monitor Output when using a germanium detector and Co source with the DSA 2000 FILTER set for a Rise Time of 5 6 us and Flat Top of 0 8 us The maximum trapezoid output level at the Monitor Output is 8 volts However be cause of the extended range of the DSA 2000 s digital filter the digital to analog con verter which generates the monitor output can be over driven past its 12 bit range When this happens the monitor output will limit or clip at 8 volts or sightly above Offsets in the digital filter are dependent on gain selection rise time selection and de tector noise The digital offset can become proportionately large for long rise time set tings and may cause the Monitor Output DAC to be driven past its 12 bit range When this happens the dynamic range of the Monitor Output may reduce from its nominal 8 volt full scale range As long as the MCA memory or spectral range is not exceeded a reduction in the Monitor Output dynamic range will not affect the MCA spectrum since the dynamic range of the digital filter is significantly larger than that of the Monitor Output 49 50 Using the Monitor Output Scope Vert 2 V div Horiz 2 5 us div Ichi iVa M Sps Cht Y 1 24V Figure 37 A Typical Trapezoidal Monitor Output Figure 38 shows the type of waveform ge
37. as adjusted the flat top variations in detector rise time will not affect the output The instructions presented below assume the DSA 2000 is set up as outlined in Spec troscopy System Setup on page 53 The BDC does not change the Rise Time setting use the 5 6 us default value or set as desired For additional information on setting the Rise Time and Flat Top please refer to Appendix B Performance Adjustments To initiate the Auto BDC process perform the following steps 1 Adjust the Co radioactive source for an incoming count rate ICR between 1 and 20 kHz The Auto BDC may fail to converge if the incoming count rate is not within this count rate range The ICR can be verified by viewing the Status Page Select MCA Adjust Status from the Acquisition and Analysis window then Update to update the ICR status whenever the radioactive source is adjusted Note Although any radioactive source may be used the most accurate adjustment is obtained using simple sources such as Co Cs or 6Co The Auto BDC op erates properly with spectral peaks located within 25 to 100 of the system dynamic range However best performance is obtained with the system gain adjusted to place the primary peaks within the top 75 to 95 of the system dynamic range Once the Auto BDC has completed replace the calibration source with the sample to be analyzed and adjust the system gain as required 2 Initiating Auto BDC Note The Gain
38. bilizer MCS and High Voltage Power Supply are all controlled from the host computer rather than manually with front panel knobs and switches To begin click on the MCA entry in the Definition Table that you want to set up Device Setup The Devices menu shown in Figure 14 sets the parameters for the DSA 2000 s MCA and associated devices Some Devices are disabled grayed out because they do not have any settable parameters Of the enabled Devices only the MCA and Sample Changer have user selectable parameters The remainder default to their only parame ter Internal 21 22 User Interface and Controls MEA sample Changer ADC MA Stabilizer Amplifier High Voltage Power Mom acum DSP Gain DSP Filter MCS Pulser Figure 14 The Device Setup Menu MCA Selecting the MCA command in the Devices menu pops up the Dialog Box shown in Figure 15 which lets you set the Ethernet address for the DSA 2000 and select the type of input Full Memory Address Select the DSA 2000 s full memory size Station Address Since the DSA 2000 is connected to the system through an Ethernet you must specify the network address that will be used to communicate with the module Enter the DSA 2000 s four digit address in the Station Address text box Defining an MCA MCA for input DETO1 MCA Full Memory Cik 2k 4k Cek Bk amp 32k B4k DSs4 2000 PHA C MCS C BOTH Station Addre
39. by increasing the Guard Time For problematic detectors this will reduce spectral distortion at high count rates but at the expense of reduced throughput PUR Guard Setup The default PUR Guard Time is 1 1x This Guard Time is minimum and does not ex tend the pile up rejection interval beyond the peaking time For events that exhibit sec ondary time constants or other anomalies measure the pulse width from the leading edge to where it returns to the baseline and becomes stable This is shown as time Ty in Figure 46 The required guard time is determined by dividing Ty by the Peaking Time 1 1T Tria Top 73 74 PUR LTC Operation For example e The filter rise time is set to 5 6 us and the flat top is set to 0 8 us The Peaking Time is 1 1 x 5 6 Us 0 8 us 7 0 Us T for a stable baseline is 15 0 us e The desired guard time setting is T Peaking Time 15 0 7 0 2 1 If the calculated guard time falls in between available selections set the PUR Guard for the next higher setting The pileup rejection interval will now be extended beyond the peaking time Subsequent events that occur within the pileup reject interval of 15 us will be rejected After this instance the anomaly associated with the tail of the previous pulse is over and subsequent events can be accepted As noted earlier extending the PUR interval by adding Guard Time will degrade throughput Highest throughput is obtained with the PUR Guard set for minimum
40. ce peak area variation using the default LT Trim setting is typically less than 3 for dead times of 50 The discriminating user can improve performance further for the intended application by calibrating the system using the Two Source Method and optimizing performance using the LT Trim The following steps are designed to demonstrate and verify the effectiveness of the Live Time Correction function The verification optimization process uses the Two Source Method which assumes that source A is 6Co and source B is Cs The 1173 2 keV peak of Co will be used as a reference The upper peak at 1332 5 keV is not a good choice because the sum peak of 3 Cs at 2 x 661 6 1323 2 keV would in terfere with the measurement 1 Connect and set up the Model DSA 2000 as described in Spectroscopy System Setup on page 53 2 Verify LTC is set ON 3 Pole Zero Compensation The Pole Zero was previously adjusted and it should not be necessary to do it again If for some reason readjustment is necessary please follow the directions in Detector Matching on page 58 4 Set the MCA s preset to 500 Live seconds 5 Position the Co source near the Ge detector and adjust for an incoming count rate of 2 to 5 keps The 1173 2 keV Co reference peak should be at approximately 80 of the spectral full scale range If necessary adjust the DSA 2000 gain to properly locate the peak Note Once in place the source shoul
41. d distortion of the MCA energy peak shape The effect becomes more pronounced with large detectors and high energies Low energy tailing often indicates the presence of ballistic deficit For traditional ana log signal processing users are forced to manually inspect the peak shape of the MCA energy spectrum and optimize the shaping time selection For detectors that exhibit ballistic deficit the shaping time is often increased to improve resolution but at the expense of throughput The Trapezoidal shaping function employed in the DSA 2000 allows independent adjustment of the Rise Fall time and Flat Top The Rise Fall time sets the noise filtering characteristics and the Flat Top adds sufficient time for the charge to be collected and integrated As a result the ballistic deficit effects can be minimized by adjusting the Flat Top time without burdening the Rise Fall time This results in a overall shorter processing time and higher throughput compared to Gaussi an shaping and traditional analog signal processing Detector Matching Optimizing the Flat Top on the DSA 2000 is automatic and easy manual adjustment is not necessary Automatic adjustment of the Flat Top time is performed by initiating the Auto BDC Ballistic Deficit Correction function A sophisticated algorithm mea sures the detector pulses determines the range of detector rise times and sets the digi tal filter trapezoid flat top for full charge integration After the DSA 2000 h
42. d not be moved or altered in any way for the re mainder of the experiment 6 Clear the MCA and acquire a spectrum for 500 live seconds Record the net area of the 1173 2 keV Co peak source A PUR Guard 7 To the Co source add approximately 25 kcps of 3 Cs to make the total incoming rate 30 kcps 8 Clear the MCA Collect a new spectrum for 500 live seconds and record the net area of source A 9 Compare the net area of the 1173 2 keV Co peak acquired in step 6 and compute the percentage change 10 If improvement is needed try adjusting the LT TRIM slightly and repeat steps 6 through 9 until an optimum setting is achieved The LT Trim function is located on the Gain Device Adjust screen The value can be decremented incremented over a range of 0 to 1000 using the adjust slide bar the default setting is 250 Since the detector source geometry was maintained and the preset Live Collection time was held constant the Co 1173 2 keV net area can be used as a standard when comparing the effect of adding background counts Cs 661 keV Note Lowering the LT Trim value will increase the system dead time and counts in the reference peak area at high count rates 11 Set the LTC ON OFF switch to Off Repeat steps 4 through 9 Compare the deviation of source A s spectrum when the LTC is ON and the LTC is OFF With the LTC OFF large changes will be observed in the reference net peak are as a function of co
43. dit ing a definition Just select the entry you want to change and apply the commands as before then Save the Definition file 35 User Interface and Controls The New Command If you want to create a totally new MCA Definition the File menu s New command clears the definition table so you can begin a new definition Because New is a destructive operation selecting it will cause the program to ask for a confirmation in one of two ways 1 If the Definition currently being displayed has not been changed since it was last saved no asterisk in the Title Bar you will be asked if you want to erase the current Definition Click on OK to erase it or Cancel to return to the Input Definition Editor 2 If the Definition currently being displayed has been changed but not saved you will be given a chance to save it The Input Definition Report The File menu s Report command always saves to a disk file but if you click on Yes in the dialog box that pops up you can send the report to a disk file and print the re port as well Click on No to save it to a disk file without printing the report Using MCA Definition Tables The whole purpose behind building MCA Input Definitions is to let the DSA 2000 know the number and types of MCAs you ll be using with your system You do this by loading one or more MCA Definition Files into the MCA Runtime Configuration Da tabase This database is shared by all of the programs which make up the
44. e DSA 2000 s power switch 1 0 located on the lower left side of the front panel controls power to the instrument Power is enabled when the switch is in the 1 posi tion and disabled when the switch is in the 0 position The associated LED glows when the instrument is powered The Status Indicators The DSA 2000 s front panel indicators show the status of power on Ethernet commu nication activity with the host computer detector high voltage power supply acquisi tion and the automatic BDC function POWER Green LED indicates when the instrument is connected to the ac mains and the power switch is on FAULT Yellow LED indicates a Ethernet communication fault has oc curred with the host computer COMM Tx Green LED indicates Ethernet transmit activity from the DSA 2000 Front Panel COMM Rx VOLTAGE kV 5 kV 1 3kV 5 kV HV ON HV FAULT DEADTIME PUR ON ACQUIRE ICR BDC BUSY Green LED indicates Ethernet receive activity from the host computer Red 20 segment horizontal LED bar graph indicates the current voltage setting of the detector high voltage power supply 0 to 5000 volts full scale with each segment representing approxi mately 250 volts Green LED indicates the high voltage power supply polarity and range is set to the positive 5000 volt range Green LED indicates the high voltage power supply polarity and range is set to the positive 1300 volt range Green LED ind
45. e complex than the MID Wizard was designed to han dle you ll have to use the MID Editor to create your definition It is covered in detail starting on page 16 The MID Wizard To use the MID Wizard open the Genie 2000 folder and select the MID Wizard icon to start the definition process Step 1 The first screen Figure 5 lets you select the MCA you want to create a definition for Choose DSA 2000 then select the Next button 13 User Interface and Controls MID Setup Wizard Step 1 To start select an MCA device from the list below Available MCAs Accu5pec A AccuSpec B AccuSpec Nal AccuSpec Nal AlM AlM DSP Desktop InSpector InSpector lt Back Next gt Cancel Help Figure 5 Selecting the MCA Step 2 The Step 2 screen will ask you to define the MCA s Full Memory number of inputs and Ethernet address as shown Figure 6 In addition you can specify whether the in put is PHA or MCS MID Setup Wizard Step 2 Enter station address of the MCA r MCA Full Memory Cik Ck Ck Cok Cb 3k fF Bk PHA C MCS pz r Station Address Hex er lt Back Cancel Help Figure 6 Defining the Full Memory and the Address Steps 3 and 4 You won t see the screens for Steps 3 and 4 these steps are not used when setting up a DSA 2000 14 The MID Wizard Step 5 The screen in Figure 7 asks you to define the high voltage power supply s Range V
46. e possible to minimize performance degradation by fine tuning the pole zero manually To adjust the Pole Zero manually refer to Manual Pole Zero Matching on page 61 To initiate the Auto Pole Zero process please follow the directions below Detector Matching Note Adjust the Co radioactive source for an incoming count rate ICR between 1 and 20 kHz The Auto Pole Zero may fail to converge if the incoming count rate is not within this count rate range The incoming count rate can be verified by looking at ICR on the MCA Adjust Status Page of the Acquisition and Analysis window Select Update to update the ICR Status whenever the radioactive source is adjusted The incoming count rate can also be determined by connecting a scaler to the ICR connector on the DSA s rear panel Although any radioactive source may be used the most accurate adjustment is obtained using simple sources such as gt Co 37Cs or 6Co The Auto P Z oper ates properly with spectral peaks are located within 25 to 100 of the sys tem dynamic range However best performance is obtained with the system gain adjusted to place the primary peaks within the top 75 to 95 of the sys tem dynamic range These recommendations also apply when adjusting the Pole Zero manually on systems without Auto Pole Zero Once completed re place the calibration source with the sample to be analyzed and adjust the sys tem gain as required In the MCA Adjust screen
47. ectral interference 1 Connect the Model DSA 2000 and set it up as described in Spectroscopy System Setup on page 53 2 For the following demonstration of the Pileup Rejector a Co source will be used Due to the lower energy of this source the system gain will need to be increased set the gain as follows Coarse Gain x40 Fine Gain x1 6000 SF Gain 0 0000e7 67 68 Note 10 PUR LTC Operation Leave the remaining functions as previously setup Verify that the LTC mode is set on the function is located on the Gain Device Adjust screen The pile up rejector PUR and Live time corrector LTC operate as an inte gral system The LTC On Off function controls both the PUR and the LTC Pole Zero Compensation The Pole Zero was previously adjusted and it should not be necessary to do it again If for some reason readjustment is necessary please follow the directions in Detector Matching on page 58 Adjust the DSA 2000 Gain to locate the 122 keV 57Co peak in channel 3500 This is to allow the Pileup region and sum peaks to be viewed in the upper half of the spectrum Readjust the Co incoming count rate ICR for 50 kcps Set the MCA preset to 60 seconds Live Time Set the MCA acquire to OFF clear the memory and set acquire to ON Accumulate a spectrum with the LTC ON Save the spectral file or print the spectrum or make note of the background counts and sum peaks for comparison with
48. ects communication at 38400 baud from the program download utility running at the host computer If no computer is connected and thus proper com munication is NOT established then control is passed to the Main Program which outputs the remaining text at 9600 baud The instrument s CPU program versions are displayed CI DSA 2000 Main Master Program Versions ain VO0 95 Boot V00 07 The DSA 2000 initialization Module initialization Leds init OK The instrument s processor performs simple I O operations to the front pane logic OK indicates that Read Write operations to the front panel logic were performed within the allowed time FAIL would typically indicate failure in the front panel or ICB logic SNIC init OK The instrument s processor performs initialization sequence on the SNIC ether net communication processor OK indicates the SNIC responded properly to its initialization including its own internal loopback tests FAIL would typically indicate failure in the I O logic or SNIC processor Timers init OK 103 104 Using The Diagnostic Port The instrument s processor performs initialization sequence on the integral timer hardware OK indicates the timers responded properly to its initialization FAIL would typically indicate failure within the AIM cpu itself as the timers are integrated within the cpu package Buffers init OK The instrument s processor performs initialization to essent
49. ed on the computer and the system will have been configured and tested at the factory Initial Setup Initial Setup To properly install and apply power to the DSA 2000 Spectrum Analyzer please ver ify the following Operating Environment Be sure you are operating in the operating environment specified for the instrument The temperature and humidity specifications can be found in Appendix A Specifica tions Instrument Cooling The DSA 2000 Spectrum Analyzer is fan cooled The fan inlet is located at the right side of the rear panel and exhaust holes are located on the left and right side of the bot tom cover near the front panel For optimum cooling be sure to leave space behind and below the instrument and keep the air intake and exhaust holes free of any ob structions Connecting to the AC Line Power The DSA 2000 Spectrum Analyzer can operate over a voltage range of 90 to 259 volts ac at 47 to 63 Hz and may require up to 60 watts of power Your DSA 2000 should have been configured at the factory for the line voltage specified in your order Please verify that the Power Entry module voltage selection matches the ac line input power The module s voltage selection is visible through the window in its cover If it is necessary to change the Module s voltage selection or fuses detach the ac Line cord from the DSA 2000 and follow the steps in Appendix C Voltage Selection WARNING Turn off the DSA 2000 and disconnect the input
50. ee we Dk SP a ee hae thes 35 Editing the Definition 00 0 0 0 0000002 eee ee 35 The New Command ls A E te a Webel E E a 36 The Input Definition Report 2 2 0 0 0 0 00000002 00000008 36 Using MCA Definition Tables 2 a 36 Viewing the Current Database e 36 Loading and Unloading Definitions o a 37 Loading the Database sms wae la OR wee AR IE ed 37 Unloading the Database 2 2 e 38 Acquisition Window Adjust Screen 2 2 a 39 Stabilizer Param ters ceci goals arte BAA aoe Era a a Boe aot 39 DSP Gain Parameters ye See rs Se Be ee ee bes 41 DSP Filter Parameters voi Seip 4 a a Ko ia Wa ee 42 MES Parameters 2 3 sh pe wh Sot A a oa a a ot AA A A 44 High Voltage shes Pee eee SA ee ee DBA Doe ES et ba ee ed 45 Using the DSA 2000 with Genie VMS 0000000002 ee eae 45 Configuring the Device Settings 2 2 0 20 0002 eee eee ee 46 Using the Monitor Output 49 Trapezoid Outputs Sisy coh ate viele wg Aa Ae a eo kA Bare ak oe Sa 49 Using the Monitor Output to Verify System Gain o o e e 51 Basic Spectroscopy Operation 53 Initialization and Self Diagnostics at Power On o o e o 53 Spectroscopy System Setups s oer 24 4 det peace GO A tee oe Ae Be do ea ed Detector Matching Automatic Pole Zero Matching DSA 2000A only Manual Pole Zero Matching Au
51. elections ranging from 0 to 3 us The flat top can also be set using the Auto BDC function in the Acquisition and Analysis application For more information on using the Auto BDC function please refer to Automatic Ballistic Deficit Correction on page 64 MCA Settings If you choose either MCS mode or Both mode you ll also have to select the MCS Disc Mode as shown in Figure 22 Note This window s initial focus is on the Cancel button pressing the keyboard s ENTER key after making changes in this dialog box will cancel the changes Be sure to click on OK to accept the changes 31 User Interface and Controls MCS for input DETO1 Figure 22 Choosing the MCS Disc Mode Disc Mode The Disc Mode control establishes the MCS mode to be used Selecting FDisc enables the MCS s fast discriminator mode all incoming events processed by the DSP are counted Selecting TTL enables the MCS s TTL mode causes all TTL events as seen at the MCS IN rear panel connector to be counted Selecting ROI enables the ROI discrimination mode meaning that all incoming events processed by the DSP that fall within the selected discrimination window are counted Input Settings The Input command is used to change the name of the Input and set up the structure of its memory via the Dialog Box shown in Figure 23 These commands are not avail able in the Acquisition and Analysis application Define Input Input name DE
52. elects either POSITIVE or NEGATIVE input polarity INH POLARITY Selects either POSITIVE or NEGATIVE inhibit polarity PUR GUARD Selects guard time multiplier GT in increments of 1 1 1 3 1 5 1 7 1 9 2 1 2 3 and 2 5 to reject trailing edge pile up in the event of detector preamp anomalies guard time extends from peak detect time by the amount GT x Tp TriatTop gt GT 1 selects minimum resolving time for maximum throughput FDISC MODE AUTO Fast Discriminator FD threshold is optimized automati cally MANUAL Fast Discriminator signal is over a range of 0 100 INHIBIT MODE NORM the system is gated off while external INHIBIT is set true RESET the inhibit time is automatically extended to account for the system overload recovery time or while external INHIBIT is set true COINC MODE In the COINCidence ANTIcoincidence mode a positive GATE pulse enables disables the conversion of the present input 79 Specifications FDISC SETTING Allows adjustment of the fast discriminator threshold level when MANUAL DISC THRES is selected The adjustment range is 0 to 100 the front panel ICR LED serves as a user aid when manually setting the Fast Discriminator threshold LT TRIM Allows adjustment of the trapezoid pulse evolution time or dead time to op timize Live Time Correction LTC performance The adjustment range is 0 to 1000 the default value of 250 provides good LTC performance for a wide range of a
53. erials and workmanship under normal use for a period of one 1 year from the date of shipment We warrant proper operation of our software only when used with software and hardware supplied by us and warrant that our software media shall be free from defects for a period of 90 days from the date of shipment If defects are discovered within 90 days of receipt of an order we will pay for shipping costs incurred in connection with the return of the equipment If defects are discovered after the first 90 days all shipping insurance and other costs shall be borne by you LIMITATIONS EXCEPT AS SET FORTH HEREIN NO OTHER WARRANTIES WHETHER STATUTORY WRITTEN ORAL EXPRESSED IMPLIED INCLUDING WITHOUT LIMITATION THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE OR OTHERWISE SHALL APPLY IN NO EVENT SHALL CANBERRA HAVE ANY LIABILITY FOR ANY SPECIAL INDIRECT OR CONSEQUENTIAL LOSSES OR DAMAGES OF ANY NATURE WHATSOEVER WHETHER AS A RESULT OF BREACH OF CONTRACT TORT LIABILITY INCLUDING NEGLIGENCE STRICT LIABILITY OR OTHERWISE EXCLUSIONS Our warranty does not cover damage to equipment which has been altered or modified without our written permission or damage which has been caused by abuse misuse accident or unusual physical or electrical stress as determined by our Service Personnel We are under no obligation to provide warranty service if adjustment or repair is required because of damage caused by other than ordinary
54. etector 4 Use the FDisc setting slider bar in the Gain Device Adjust screen to set the fast discriminator threshold just above the system noise as indicated in step 5 5 The following steps optimize the discriminator sensitivity to insure the threshold is at its lowest setting just above the noise level Operation with Reset Preamps Adjust the FDisc Setting to 0 The ICR LED indicator continuously glows green Next increase the FDisc Setting level until the ICR LED indicator is no longer on continuously but shows low activity by blinking green occasionally The fast discriminator threshold is properly set Note With the Fast Discriminator in the manual mode the threshold must be re checked and adjusted if the Detector Preamplifier is changed or the DSA 2000 s GAIN is changed Operation with Reset Preamps The DSA 2000 Digital Spectrum Analyzer is fully compatible with most pulsed reset preamplifiers Reset preamps use an electronic circuit as opposed to a feedback resis tor to restore the preamp back to a reference level As a result the preamp output is a succession of step functions that staircase or ramp up to an upper limit or threshold that initiates a preamp reset Configuring the Preamp Reset Mode When using a Transistor Reset Preamp TRP it may be necessary to disable the Reset Delay feature if present on the associated preamplifier If the Reset Delay feature is left enabled small phantom peaks may result
55. f 50 Hz 100 Hz 500 Hz and 1 kHz edge triggered trigger edge dependent on detec tor s high voltage polarity HC output through 33 Q series resistor Note detector must be equipped with Canberra precision dual amplitude pulser 10 Base 2 Thin wire Ethernet rear panel BNC AUI Ethernet AUI rear panel 15 pin female D connector Front Panel Indicators ADV Sample changer advance logic signal which enables external sample changer movement polarity selected by computer pulse width 2200 ms TTL compatible logic low lt 0 4 V logic high 22 4 V PREAMP Provides 24 V 12 V 43 and ground for standard preamplifiers 24 V at 50 mA max 12 V at 100 mA max rear panel 9 pin D type connector Front Panel Indicators POWER Green LED indicates ac power is on HV ON Green LED indicates HVPS is on HV FAULT Yellow LED indicates a high voltage fault e g detector warmup loss of high voltage 5 kV Green LED indicates HVPS polarity and range is set to 5 kV 1 3 kV Green LED indicates HVPS polarity and range is set to 1 3 kV 5 kV Green LED indicates HVPS polarity and range is set to 5 kV VOLTAGE kV 20 segment horizontal bar graph indicating O to 5 kV DEADTIME 20 segment horizontal bar graph indicating O to 100 deadtime PUR ON Green LED indicates PUR function is on or enabled ACQUIRE Green LED indicates MCA is acquiring FAULT Yellow LED indicates Ethernet communicati
56. fy that the setting matches the ac line input power look through the window on the power entry mod ule s cover If it becomes necessary to use a different setting the voltage selection is easy to change The power entry module voltage selections are 100 V ac 120 V ac 220 V ac and 240 V ac allowing the DSA 2000 to operate over a voltage range of 90 259 V ac To change the DSA 2000 power supply s input voltage turn the power supply off and detach the power cord from the ac main supply WARNING Leaving the ac input power connected while working with the power entry module can result in serious injury or death Changing the Voltage Selection 1 Open the power entry module s cover using a small bladed screwdriver or similar tool to pry up the cover s tab which is just above the voltage selection viewing window Let the cover open to its resting position 2 Pull the Selection Wheel straight out of the housing Figure 52 A small bladed screwdriver or similar tool may be required to pry it out of the housing 3 Turn the wheel until the desired line voltage is facing you then push the Selection Wheel back into the module until it clicks into place If the ac voltage from the power mains is not available on the Selection Wheel select the next higher setting on the card For example if the mains voltage is 105 set the Selection Wheel to 120 volts for highest efficiency and lowest temperature rise When changing the voltage
57. hibit time is the OR of the external INH signal and the DSA 2000 s reset disable time whichever is longer Positive true or negative true sig nal polarities user selectable minimum pulse width is 1 us loading 4 7 KQ logic high 2 3 6 V logic low lt 1 V 0 to 12 V maximum rear panel BNC connector HV INH Logic low or ground inhibits the HV output max logic low lt 0 7 V logic high 22 0 V or open circuit enables loading 4 7 KQ pull up resistor to 5 or 12 V pull up voltage is computer selectable MCS IN MCS counts input HCT compatible logic low lt 0 9 V logic high 2 3 2 V minimum pulse width gt 10 ns maximum rate 250 MHz PHA S S Input starts and stops PHA acquisition acquisition time determined by the arrival time of two sequential pulses start and stop are negative edge triggered TTL compatible 10 KQ pull up resistor to 5 volts logic low lt 0 8 V logic high gt 2 0 V minimum pulse width 210 ns 75 Outputs 76 Specifications MCS S S Input starts and stops MCS acquisition acquisition time determined by the arrival time of two sequential pulses start and stop are negative edge triggered TTL compatible 10 kQ pull up resistor to 5 V logic low lt 0 8 V logic high gt 2 0 V minimum pulse width 210 ns RDY Sample changer ready input holds off acquisition until the sample changer mechanism signals that the sample is in the proper position level triggered computer selectable polar
58. ial memory buffers used by the program Acquisition memory is treated separately OK indicates no problems encountered FAIL would typically indicate failure within the memory logic Ade init OK The instrument s processor performs initialization ADC acquisition logic for both PHA and MCS OK indicates no problems encountered FAIL would typi cally indicate failure within the acquisition logic Acq memory OK The instrument s processor performs battery back retention test to the ADCs battery backed memory OK indicates that the memory properly retained its data INIT indicates that the test failed and the memory contents have been re initialized The retention test will fail if the memory s backup power supply de pleted below the value necessary for proper retention DMA Channel OK The instrument s processor performs simple memory transfers via DMA OK indicates no problems encountered FAIL would typically indicate failure within the AIM cpu itself as the DMA channels are integrated within the cpu package or withing the I O decode logic which is essential in synchronizing DMA transfers Ethernet Adrs 00 00 AF OO AC B1 The ethernet address for the DSA 2000 is printed here for convenience This address is programmed into permanent memory at the factory Ethernet OK Type Thinnet Initialization The instrument s processor performs automatic ethernet detection test by actu ally sending a test packet to
59. icates the high voltage power supply polarity and range is set to the negative 5000 volt range Green LED indicates the detector high voltage power supply in on and high voltage could be present at the rear panel high volt age connector Yellow LED indicates a high voltage fault condition such as HV inhibit or high voltage overload Red 20 segment horizontal LED bar graph indicates the average system dead time in increments of 5 Green LED indicates the PUR LTC Pileup Rejection Live Time Correction function is on or enabled Green LED indicates when data acquisition is active Green LED indicates when data acquisition is active Green LED indicates incoming count rate activity from the asso ciated detector also serves as a user aid when setting the Fast Discriminator Threshold manually Green LED indicates an automatic BDC operation has been ini tiated and is in process Controls and Connectors Rear Panel This is a brief description of the DSA 2000 s rear panel connectors For more detailed information refer to Appendix A Specifications TRP INH HY INH MONITOR Ick Isp US GATE MCS IN MES S S PHAS S 50 60 HZ 60W oo 00000000 AMP IN PREAMP ADY E Es annn DIAGNOSTIC 10Base2 gt gt Figure 2 Rear Panel Connectors Detector Signal Processing Connectors HV High voltage output for detector bias programmable range and polarity SHV connector TRP INH Reset pream
60. inition you can 1 Click on your choice then click on the Add button or 2 Double click on your choice Either way yov Il see an entry added to the MCA Definition Table for each such selection you make When you ve added your MCA to this definition click on the DONE button to return to the main MID window Building an MCA Definition 4 Add MCAs to Definition Table Available MCAs AccuSpec A AccuSpec B AccuSpec Nal AccuSpec Nal Figure 11 The Add MCA Dialog Figure 12 shows the result of using this process to add a single DSA 2000 MCA to the Definition Table Please remember that this display as well as many others in this chapter are examples of what you might see your display may not be identical Py MCA Input Definition Editor local Untitled Database Edit Devices Settings Summary Help Input Size ADC MXR Stab Amp HY DSA 2000 DETOI Figure 12 A DSA 2000 Has Been Added to the Table 19 User Interface and Controls Interpreting the Definition Entry As you can see in Figure 12 adding the entry put more than just the name of the MCA in the definition table We ll take a brief look at the other items in the entry now As we get further into the definition process we Il cover them in greater detail Note the letter following the unit number in each Definition Table item an M indicates a manu ally controlled unit and a P indicates a programmable unit MCA This is the type of MCA device being u
61. ity TTL compatible 10 KQ resistor to ground logic low lt 0 8 V logic high gt 2 0 V DIAGNOSTIC Diagnostic port RS 232 rear panel 9 pin male D connector MONITOR Provides viewing of sampled data reconstructed in time as a user aid to assist with setup digitally filtered Trapezoidal Triangular pulse amplitude linear to 8 V 8 V max Z u 50 Q short circuit protected front panel BNC connector out ICR ICR Incoming Count Rate provides a standard TTL logic signal frequency corresponds to input count rate positive true width 150 ns Z u 50 Q rear panel BNC connector out HV High voltage output programmable range and polarity 5000 V de with 100 uA output current capability or 1300 V dc with 500 uA output current capability resolution of 1 part in 4096 rear panel SHV connector isolated from chassis ground by 47 Q resistor and parallel 33 WH choke MSP Most Significant Pulser logic signal used to control high amplitude pulse from associated precision dual amplitude pulser computer selectable rates of 50 Hz 100 Hz 500 Hz and 1 kHz edge triggered trigger edge dependent on detector s high voltage polarity HC output through 33 Q series resistor Note detector must be equipped with Canberra precision dual amplitude pulser LSP Least Significant Pulser HC compatible logic signal used to control low ampli tude pulse from associated precision dual amplitude pulser computer selectable rates o
62. l information and techniques for adjusting pole zero refer to P Z Matching Using a Square Wave Generator on page 89 P Z Matching Using a Ge Detector and Co 1 Adjust the radiation source count rate to be between 2 kcps and 20 kcps Observe the trapezoidal waveform on the monitor output 2 Verify that the preamp type in the filter device MID editor is set to RC Adjust the Pole Zero slider bar located in the Filter Device Adjust screen so that the trailing edge of the trapezoid pulse returns to the baseline with no overshoots or undershoots Figure 41 shows the correct setting of the P Z adjustment while Figures 42 and 43 show under and over compensation for the preamplifier decay time constant As illus trated for correct P Z compensation the monitor output signal should have a clean re turn to the baseline with no bumps overshoots or undershoots Note Some systems may exhibit small undershoots when the monitor output returns to baseline These arise primarily from secondary time constants associated with the detector preamp system If an undershoot is present and is less than 20 mV its impact on performance is insignificant However if small shaping undershoots are present they should not be confused with undershoots caused by preamp matching misadjustment which exhibit a much longer time con stant and have a larger performance impact At high count rates P Z matching misadjustment will affect spectral peak sha
63. lay the MCA type that is being used for each entry If you choose By Input the MCA and Input columns will be reversed in the display and the Inputs will be sorted alphabetically You can choose either method but in the case of systems with a large number of in puts By Input is an easier display to understand than By MCA 34 Editing an MCA Definition Editing an MCA Definition To edit an MCA Definition use the MID Editor s File Open command to select the file and open it in the editor Editing a File in the Runtime Configuration Database If the Definition you want to edit has been loaded into the MCA Runtime Configura tion Database it must first be unloaded before it can be opened in the editor See Un loading the Database on page 38 for instructions Viewing the File Details If you re not sure which file you want to edit select a file then click on the Info but ton to see further information about the file as shown in Figure 25 File Name SAMPLE File Descriptor Sample Input Definition File File Type MCA Input Definition Editor Version V2 8 OK Figure 25 The File Info Display The key piece of information here is the File Descriptor which you added when the file was first saved This should help you decide if the file you selected is the one you want to edit Editing the Definition All of the menus and commands available for defining an MCA are also used for e
64. llowing section describes those parameters for the DSA 2000 that can be ac cessed from the acquisition windows Adjust dialog screen Note that the Adjust screen for a given device may actually be composed of several screens which are ac cessed by using the Next Prev pushbuttons More detail information about specific function can be found in Basic Spectroscopy Operation on page 53 PUR LTC Oper ation on page 67 and Performance Adjustments on page 86 Stabilizer Parameters The Stabilizer settings screen Figure 29 for the DSA 2000 contains the following controls e Stab C HWPS C MCS C Gain C Filter Gain centroid Gain window Gain spacing Gain mode Next DK 8 chs 64 chs E ae o Figure 29 The Adjust Stabilizer Dialog Gain Centroid Sets the centroid in channels of the reference peak at the high end of the spectrum for gain stabilization Gain Window Sets the width in channels of the upper and lower sampling windows on either side of the gain reference peak Gain Spacing Sets the spacing in channels between the upper and lower sampling windows The windows should be placed so that a shift in the reference peak reflects a significant change in count rate through the window For broad peaks the spacing should be set so that the windows edges are not on the flat part of the peak Gain Mode Sets the Gain Stabilization mode to Off On or Hold Off disables gain stabilization and sets the correction adjustmen
65. ly non piled up events to be processed and stored into the spectrum The result is a reduced number of counts in the pileup region and reduced spectral interference for improved quantita tive measurement and analysis To compensate for dead times associated with rejected pulses and amplifier processing times the Model DSA 2000 generates a dead time DT signal which extends the col lection time by the appropriate amount Pileup Rejection With a Live Source The pileup rejector monitors the signal processing activities of the fast discriminator fast channel and digital filtered signal slow channel and allows only signals result ing from a single detector event to be processed and stored in the spectrum The fast discriminator detects the arrival of input events and is capable of discriminating be tween multiple events separated by less than 500 ns If the fast discriminator detects two or more events within the processing time of the slow channel the event is con taminated by pileup and is discarded The fast discriminator threshold is automatically adjusted just above the system noise level for accurate operation However for the discriminating researcher or special cir cumstances the threshold can be optimized manually For instructions on adjusting the threshold manually see Manual Fast Discriminator Threshold on page 92 The following steps will demonstrate the operation of the Pileup Rejector and its abil ity to reduce sp
66. me generated by the DSA 2000 When setting the inhibit time manually set the TRP Inhibit to NORMAL The TRP In hibit mode is selected in the Gain Device Adjust screen The inhibit time of the preamp must now be manually adjusted to encompass or extend to the point where the trapezoid signal returns back to the baseline Using a Tee connector connect the preamp s Inhibit signal to the INHIBIT BNC connector located on the rear panel of the DSA 2000 Monitor the preamp s Inhibit signal and the DSA 2000 s Trapezoid signal viewed on the Monitor Output using an oscilloscope Use a clamp box such as the Canberra Model LB1502 when viewing the Trapezoid signal to prevent scope overload 95 Performance Adjustments Trigger the Oscilloscope on the leading edge of the preamp Inhibit signal Adjust the preamp inhibit time so that it returns to zero volts after the negative Trapezoid nega tive overload signal returns to the baseline see Figure 51 Consult the Detec tor Preamp Operator manual for this adjustment Figure 51 Setting the Reset Preamp Inhibit Pulse Width The DSA 2000 s overload recovery time is approximately 40 us with the Rise time set to 5 6 us and Flat Top set to 0 8 us and using a Canberra Model 2101 preamp and Co source 96 C Voltage Selection The DSA 2000 ac input power requirement should have been preconfigured at the fac tory for the standard line power of the destination country To veri
67. minated This could result from a fault in the DSA 2000 hardware or a Ethernet communication problem with the network or host computer Spectroscopy System Setup Figure 39 shows a typical gamma spectroscopy system Perform the following steps to set up your spectroscopy system 1 If you are using a detector with a reset preamp please refer to Operation with Reset Preamps on page 93 for specific instructions 2 Connect the intended Detector Preamp to the DSA 2000 Preamp power is provided by means of a 9 pin Amphenol connector located on the rear panel of the Model DSA 2000 Connect the Preamp Output signal to the DSA 53 Basic Spectroscopy Operation DSA 2000 Digital Spectrum Analyzer Host Computer ETHERNET NETWORK 10 Base 2 or AUl PREAMP RG 59 U DETECTOR MONITOR and PREAMP 2101 TRP PREAMP POWER Optional LB1500 Loop Buster Optional Oscilloscope INHIBIT OUTPUT For detectors equipped with a 2001 or 2002 preamp the INHIBIT function is not used Figure 39 Typical Gamma Spectroscopy System 2000 s AMP IN connector If the detector preamp is a reset type connect the Inhibit Output signal to the TRP INH connector on the DSA 2000 s rear panel Note Multiple ground connections to the detector preamp preamp power signal BNC cable HV power supply cable etc can setup ground loops which may be sensitive to EMI noise pickup These effects can cause resolutio
68. mmodate the detector s collection time virtually eliminating resolution degradation due to ballistic deficit The information in Appendix B Performance Adjustments tells you how to fine tune your DSA s rise time and flat top settings For applications involving the study of radiation signals that may vary with time the DSA 2000 provides a Multichannel Scaling MCS mode MCS dwell times may be set from 2 us to over 2000 seconds at input rates of up to 50 MHZ TTL or 500 kHz Analog The DSA 2000 allows MCS and Pulse Height Analysis PHA modes of op eration to be executed simultaneously Electronics in the DSA 2000 are 100 computer controlled The host computer con trols the DSA 2000 via the integral Ethernet interface built directly into the unit Soft ware control is provided via Canberra s flagship Genie ESP and Genie 2000 spectroscopy software platforms Additionally the host Genie software automatically stores a record of all the setup parameters and the instrument serial number with each spectrum file This provides a secure authentication record with each sample en suring that the parameters and instrument have not been changed from the prior cali bration or QA verification The ability of the DSA 2000 to be connected directly to an Ethernet network adds con siderably to the flexibility in operation and location of system components A net worked DSA 2000 need not be located near the host computer either f
69. n degrada tion excessive dead time and erratic count rate ICR measurement If you experience any of these problems make sure the preamp cables are tightly bundled together and routed away from EMI noise sources such as mo tors AC switching equipment computers monitors etc 54 Spectroscopy System Setup If necessary use the optional LB1500 Loop Buster provided with the DSA 2000 in series with the preamp signal cable The LB1500 Loop Buster reduces the sensitivity of the DSA 2000 input to ground loop induced noise Best per formance is obtained with the LB1500 installed at the energy or output BNC on the preamp 3 Connect the Detector Preamp High Voltage Input to the HV Output SHV connector on the DSA 2000 s rear panel The DSA 2000 provides a high quality ICB Programmable HV Power Supply 4 Turn on the DSA 2000 At power up the DSA 2000 will go through an initialization and self diagnostic process as described in Initialization and Self Diagnostics at Power On on page 53 5 The setup instructions that follow will allow you to get the DSA 2000 set up and running with a typical detector and to become acquainted with its operation For the following setup a detector with preamp gain of 500 mVMeV and a Co radioactive source will produce a 6 5 to 7 volt trapezoid signal at the Monitor Output The 1332 keV Co peak should collect in channel 6500 to 7200 on the MCA when setup for a 8192 memory or spectrum size The
70. n in Figure 53 Figure 53 The Rack Mount Hardware 100 E Using The Diagnostic Port DSA 2000 Architecture The DSA 2000s diagnostic port is a RS 232 bidirectional port used for both to diag nose problems and loading new firmware into the instrument To load firmware into the instrument a host computer with appropriate utility software is required To diag nose problems a simple VT100 compatible terminal or host computer equipped with terminal emulator software such as Windows TERMINAL is required The DSA 2000s RS 232 diagnostic connector is a 9 pin D type male connector acces sible through the instruments rear panel When connecting to host computer or termi nal a 1 1 cable is required No software or hardware handshaking is required The communication parameters are as follows Baud Rate 9600 baud for normal operation or 38400 baud when loading firmware When loading firmware the baud rate is fixed by the DSA2000 and by the download utility at the host computer Parity none Data bits 8 Stop bits 1 The DSA 2000 contains a second RS 232 port which is internal to the instrument This port is used solely to download the DSP processors main program from a host com puter It has no user interface thus its operation will be covered in a separate docu ment that will be sent with the program update diskette Initialization Typical initialization output to the terminal is as follows CI DSA 2000 Loader RA
71. nd IR aS ne A ae 8 12 4 User Interface and Controls 13 The MID Wizardsa 32 sees we kei Se eg Ae OR ed Pe ol ek ee 84 13 The MCA Input Definition Editor 2 ee ee 16 Basic Concepts es a A vote Beane A ee te RORY ohne AES ae BPR acne E 16 Starting the MCA Input Definition MID Editor o e 17 Building an MCA Definition 2 2 2 0 00 20 00000000000 0 2 ee ee 17 Adding an MCA dto Tuoro eee aa A aol dna ate ante a ate see 18 Interpreting the Definition Entry 0 2 00 00000000005 20 Deleting AMCA aiui he et he et ee oh eo Re ee ee Sh ee 20 Defining an MCArte ad 21 Device Setup s e i ee bb eb De ee be eee es Ba E ee abs 21 MCArte at GR eee aaar Ble te et 22 Sample Changers aci ts ra EEO tee de weds 23 The Settings ooo Se Slee es eb Sark eS ee bey EG e Oe SS ee ear bs 23 MCA Stine Sti 0 a be a e Mg hte ie at Md da 24 StabilizerSettings 2 4 4 ba bi fe wa A a habe ee ee hs 24 High Voltage Settings 0er n 42 4 bee wed ee dhe Soe AS ees 27 DSP Gain Settings eco mea ra ee ee ee ee 28 DSP Filter Settings Sri a 40253 al A a ee oP ad Se BAe ae 30 MCA Settings us Lok tte he eek er end EA de Bh lk ee ee deter 31 Input StI SS eh pues eek ae aed Ae vad BU ee eh eens Say baad 32 Saving the Input Definition ee ee eee 33 Changing the Summary View 2 0 2 0 a 34 Editing an MCA Definition 2 2 a 35 Viewing the Fille Details ser tidra wie ee ee
72. nd safety precautions for any internal power distribution e The use of CE compliant accessories such as fans UPS etc Any repairs or maintenance should be performed by a qualified Canberra service representative Failure to use exact replacement components or failure to reassemble the unit as delivered may affect the unit s compliance with the specified EU requirements 108 Request for Schematics Schematics for this unit are available directly from Canberra Write call or FAX Training and Technical Services Department Canberra Industries 800 Research Parkway Meriden CT 06450 Telephone 800 255 6370 or 203 639 2467 FAX 203 235 1347 If you would like a set of schematics for this unit please provide us with the following information Your Name Your Address Unit s model number Unit s serial number Note Schematics are provided for information only if you service or repair or try to service or repair this unit without Canberra s written permission you may void your warranty A CANBERRA Warranty Canberra s product warranty covers hardware and software shipped to customers within the United States For hardware and software shipped outside the United States a similar warranty is provided by Canberra s local representative DOMESTIC WARRANTY Canberra we us our warrants to the customer you your that equipment manufactured by us shall be free from defects in mat
73. nected Memory Groups This check box allows you to define a multi memory group input this box is enabled 1f the input size is defined less than the physical MCA memory size Saving the Input Definition After completing a definition use the MID Editor s File Save or Save as command to save the Definition file As a reminder you ll see an asterisk next to the name of the current definition in the Title Bar when a changed definition has not been saved CAUTION If you change an existing Input Definition saving it will set its calibrations to default and will clear the Acquisition Start time 33 User Interface and Controls The File Descriptor When a Definition is saved for the first time the Save As file dialog box is automati cally opened In that dialog box you ll see a File Descriptor field which lets you store a 32 character description with your file to make it easier to locate when you want to use it again Changing the Summary View Before going on to see how to edit an existing Input Definition Table one that you ve built previously and saved to disk there s one more menu to look at This is the Sum mary menu which is shown in Figure 24 Summary v By MCA Figure 24 The Summary Menu The Summary menu has two commands By MCA and By Input which change the order in which the information in the Input Definition Table is displayed By MCA means that the first column of the table will disp
74. nerated at the Monitor Output when the DSA 2000 is connected to a detector driven by a low energy Fe source The Filter Rise Time and Flat Top are set relatively long 18 4 us and 0 4 us respectively Scope Vert 2 V div Horiz 5 us div Figure 38 Output Range Reduced by Detector Noise Using the Monitor Output to Verify System Gain This source requires a high system gain to position its peaks in the mid to upper por tion of the selected MCA spectral range For this case the baseline or DC component of the trapezoid signal is large and signal limiting or clamping begins to occur at slightly over 3 volts Even though the Monitor Output dynamic range appears to be significantly reduced the Trapezoid waveform remains useful when verifying setup and optimizing the Pole Zero The reduction of dynamic range is proportional to the gain setting and also to the filter rise time selection as mentioned earlier In the event it is troublesome momentarily reduce the rise time or gain to a lower setting and the effect will be significantly re duced or eliminated Verify or optimize the setup when completed return to the de sired rise time and or gain setting Again the MCA spectrum is not affected due to the large dynamic range of the DSA 2000 s digital filter Note The optimum Pole Zero setting is independent of the Filter Rise Time and Flat Top setting For further information regarding the effect of wrap around when set
75. nt range is 0 to 1000 the default value of 250 provides good LTC performance for a wide range of applications LTC Mode Sets the amplifier s Pulse Pileup Rejector and Live Time Corrector When PUR is On the pileup rejector and live time corrector LTC are enabled Off disables the pileup rejector and LTC Inhibit Mode Selects inhibit mode NORMAL instructs the device to gate off while the INHIBIT In put is true In RESET mode the inhibit time is automatically extended to account for the system overload recovery time or while external INHIBIT Input is set true DSP Filter Parameters The DSP Filter settings screen Figure 31 for the DSA 2000 contains the following controls 42 Acquisition Window Adjust Screen C HVPS C MCS C Gain e Filter Rise Time Flat Top Auto BDC BLA mode Next 18 4 M 0 4 Start Auto nl Prev SLA Figure 31 The Adjust DSP Filter Dialog BLR mode Sets the baseline restorer mode With a setting of AUTO the baseline restorer is auto matically optimized as a function of trapezoid shaping time and count rate With set tings of SOFT MEDIUM and HARD the baseline restorer is set to fixed rates as selected Rise Time Symmetrically sets the rise time and fall time of the digital filter time response As with conventional Gaussian shaping the degree of noise filtering is proportional to the rise time selection The rise time can be selected from 35 rise fall times ranging from 0 4 to 28 us Flat
76. o accept detachable 3 wire line cord fused with two 5 x 20 mm fuses 4 A for 90 129 V 2 A for 193 259 V On Off control is provided by a rocker switch Physical Aluminum enclosure with forced air cooling fan Optional rack mounting kit consist ing of rack mount ears SIZE 42 5 cm wide x 8 9 cm high x 40 6 cm deep 16 75 in wide x 3 5 in high x 16 in deep WEIGHT 8 5 kg 18 73 Ib Ordering Information DSA 2000 programmable Digital Spectrum Analyzer DSA 2000A programmable Digital Spectrum Analyzer with automatic pole zero option installed 85 B Performance Adjustments This appendix describes how to make several performance adjustments adjusting the rise time and the flat top matching the pole zero manually setting the baseline re storer setting the fast discriminator threshold and operating the DSA 2000 with reset preamps Rise Time and Flat Top Adjustments 86 The digital filter employed in the DSA 2000 has a Triangular Trapezoidal weighting or shaping function The processing time Shaping is set by the Rise Time and Flat Top selections and is generally a compromise between optimizing throughput and res olution Having the ability to independently set the Rise Time and Flat Top allows greater flexibility when optimizing the processing time or shaping for a wide variety of detector applications The Rise Time sets the noise filtering characteristics of the Digi tal Filter while the Flat Top allows
77. oltage Limit and Voltage Voltage limit Voltage 1300 0v Ba a mG cm 2 1300 1300 Figure 7 Defining the High Voltage Parameters Step 6 The Step 6 screen in Figure 8 asks for a Detector Type and acquisition memory size in channels and requires that an Input Name be entered J 56 Figure 8 Assigning the Detector Type 15 User Interface and Controls Ending the Definition To complete your Input Definition select Finish The input that you just defined will be stored as an MID file named inputname MID and automatically loaded into the MCA Runtime Configuration Database described on page 36 When you select Fin ish you will be asked if you would like to define another input Answering No will close the Wizard Note that if you didn t enter an Input Name you won t be allowed to exit the Step 6 screen If the name you entered is the same as the name of an existing MID file the system will tell you so and go back to Step 6 to let you enter another name The MCA Input Definition Editor You ll have to use the MID Editor only if you want to change default settings for any of the DSA 2000 s programmable components The following sections tell you how to use the MID Editor to make those changes Basic Concepts We ll begin with some basic concepts that are important to understand before actually getting into the details of how you define your system s MCAs Multiple MCA Configurations
78. on fault COMM TX Green LED indicates Ethernet transmit activity COMM RX Green LED indicates Ethernet receive activity ICR Green LED indicates incoming count rate activity also serves as a user aid when setting the Fast Discriminator manually BDC BUSY Green LED indicates Auto BDC is in process 77 Rear Panel Connectors AC LINE VDE approved IEC 320 line entry module to accept detachable 3 wire power cord AUI Ethernet AUI Connector rear panel 15 pin D connector 10 Base 2 Thin Wire Ethernet rear panel BNC DIAGNOSTIC S 232 rear panel 9 pin male D connector Programmable Controls Programmable Controls Gain Continuously variable from x2 0 to x1536 COARSE GAIN x5 x15 x40 x120 x330 x960 FINE GAIN Range x0 4 to x1 6 SUPER FINE GAIN Range 0 0000e 2 to 3 000e 2 the SFG adds to the FINE GAIN Value resolution is better than 1 part in 16 000 CONV GAIN 256 512 1024 2048 4096 8192 or 16 384 channels Represents the full scale resolution of the input signal Conversion range is set to equal the selected conversion gain LLD Digital Lower Level Discriminator for minimum input acceptance level adjust ment range 0 0 to 100 of the spectrum full scale range OFFSET Offsets the spectrum to the left subtracts O to 16 128 channels in binary multiples of 128 channels ZERO ADJUST Digital Zero Adjustment 3 125 of the spectrum full scale range INP POLARITY S
79. on page 93 for ad ditional information Note Once the Pole Zero is optimized for the intended detector the digital filter pa rameters Rise Time and Flat Top can be changed as required without the need to make further Pole Zero adjustments However the Pole Zero compen sation must be readjusted if the detector is changed The Auto BDC function sets the trapezoid flat top to the correct length insuring that all the detector charge is collected for accurate energy analysis Automatic Pole Zero Matching DSA 2000A only The Automatic Pole Zero option is installed only on the DSA 2000A To verify the model number please check the serial number tag located on the rear panel The Automatic Pole Zero P Z feature will give good results for most detector appli cations and count rates However it may be necessary to optimize the P Z compensa tion manually at extremely high count rates or for specific applications where the digitally filtered trapezoid signal is prevented from returning monotonically to the baseline The feedback resistor on some RC preamps may exhibit non ideal character istics which produce multiple time constants making the tail pulse fall time non monotonic This behavior may become problematic at high count rates causing signifi cant baseline perturbations and resolution degradation Nal detectors may have multi ple time constants due to AC coupled preamps and the scintillator interactions In these situations it might b
80. onnector to accept detachable 3 wire line cord The module must be configured to match the ac main supply voltage refer to Appendix C Voltage Selection for instructions Internal Controls The DSA 2000 Digital Spectrum Analyzer is fully programmable by the host com puter There are no internal controls or jumpers that require adjustment or service by the user 3 Setup and Configuration This chapter serves as a guide to unpacking and connecting the system Software in stallation is covered in Appendix Software Installation of the Genie 2000 Operations Manual Unpacking the DSA 2000 Digital Spectrum Analyzer When you receive your DSA 2000 hardware examine it carefully for evidence of damage caused in transit If damage is found notify Canberra and the carrier immedi ately Use the following checklist to verify that you have received all of the system compo nents Basic System Your package should contain the following items e The DSA 2000 Digital Spectrum Analyzer Instrument e This Manual e One ac Line Cord e One 3m 10 ft RG 58 U 50 ohm coaxial cable e One BNC Tee Connector e One LB1500 Cable Transformer e A rack mount kit consisting of one set of rack mount ears and associated hardware System Options Your package will include any optional DSA 2000 items ordered Complete System A complete system consists of all of the items in the Basic System plus a computer All software will have been install
81. or convenience of adjustment or due to any electrical distance restrictions The unit can be located as close as possible to the detector minimizing the length of sensitive analog signal ca bles without creating operating inconveniences In addition network operation adds to the fault tolerance of larger systems Multiple computers can be located on the network and the DSA 2000 operated from any com puter Thus if a computer fails any surviving computer can continue the operation and no counting capacity in the laboratory is lost DSA 2000 s which include an A suffix in the model number DSA 2000A have the automatic pole zero option installed For the DSA 2000A the pole zero adjustment can be performed automatically the process is initiated by software command The pole zero may also be adjusted manually by the software To verify the model please check the serial number tag located on the rear panel For the DSA 2000 without the automatic pole zero option the pole zero is adjusted manually from the software 2 Controls and Connectors Front Panel This is a brief description of the DSA 2000 s front panel LED indicators and power switch For more detailed information refer to Appendix A Specifications DSA2000 VOLTAGE kY DEADTIME 0 5 0 100 ja CO W CO WN CO PRON CO er FAULT COMM Tx COMM Rx OO a Co 13 CO WAT C AQUIRE CI poe Busy Lo sn P canserra Figure 1 Front Panel Connectors Power Switch Th
82. or use with pulsed charged restoration RESET preamplifiers HVPS RANGE 5000 1300 5000 MCS VOLTAGE LIMIT Sets maximum voltage limit range depends on RANGE selec tion 1300 to 5000 V 0 to 1300 V or 0 to 5000 V STATUS ON OFF sets the HVPS ON or OFF VOLTAGE Adjusts the HVPS output over the selected voltage range and limit HVPS RESET Resets the power supply when a fault condition has occurred INH SIGNAL Sets the pull up voltage of the HV INH connector to 5 V or 12 V All Canberra detectors and preamps use 5 V Stabilizer GAIN MODE ON OFF enables or disables the Gain Mode HOLD disables the sta bilizer Gain Mode but maintains the current Gain correction factor Centroid 0 to 16 376 channels Window 1 to 128 channels Spacing 2 to 512 channels ratio 0 01 to 100 correction rate 1 to 512 correction range of 1 of full scale for Ge and 10 of full scale for Nal detectors ZERO ON OFF enables or disables the Zero Mode HOLD disables the stabilizer Zero Mode but maintains the current Zero correction factor Centroid 0 to 16376 channels Window 1 to 128 channels Spacing 2 to 512 channels ratio 0 01 to 100 correction rate 1 to 512 correction range is 1 of full scale MCS Modes Events are counted for the duration of a programmed amount of sweeps Each SWEEP incorporates a programmed amount of channels Each channel represents a DWELL duration TTL TTL pulses
83. oughput The rise time setting can be optimized separately to achieve the best count rate resolu tion compromise However the optimum flat top for a detector depends somewhat on the rise time selection Therefore the best correction for ballistic deficit will be achieved by running the Auto BDC function again or manually checking the flat top setting if the rise time is increased or decreased by a factor of two or more Triangular shaping may give enhanced resolution performance for small detectors hav ing little variability in charge collection time To set the unit for triangular shaping ad just the rise time to the desired value and set the flat top to zero P Z metening Using a Square Wave Generator Driving the preamp test input with a square wave will allow a more precise adjustment of the preamp matching 2 The DSA 2000 s GAIN RISE TIME FALL TIME and INPUT POLARITY settings should be adjusted for the intended application 3 Adjust the square wave generator for a frequency of approximately 100 Hz 4 Connect the square wave generator s output to the Preamp s TEST INPUT 5 Remove all radioactive sources from the vicinity of the detector 89 Performance Adjustments 6 Set the scope s Channel 1 vertical sensitivity to 2 V div and adjust the main time base to 10 us div 7 Observe the Model DSA 2000 s Monitor output If you are using an LB 1502 Clamp Box set the switch in the DIRECT position Adjust the sco
84. oughput pro duce a trapezoidal pulse response which has approximately one half the processing time when compared with traditional analog Gaussian shaping amplifiers These set tings result in almost twice the throughput compared to traditional analog pulse pro cessing with little or no resolution degradation in most high energy Ge detector applications The shaping times recommended for highest Resolution produce a trapezoidal pulse response with a processing time that is equivalent to traditional analog signal process ing Longer rise time and flat top settings provide better noise filtering and reduced ballistic deficit However as the system count rate increases resolution and through put may degrade as a result of increased processing time and the effects of pulse pile up The optimum shaping time constant depends on the detector characteristics such as size noise characteristics and collection characteristics preamplifier and incoming count rate Settings for typical germanium coaxial detectors have been discussed above Table B 2 lists DSA 2000 rise time and flat top settings for other common de tectors Table B 2 Settings for Other Common Detectors Detector Rise Time Flat Top ms Scintillation Nal Tl 0 8 0 2 or 1 2 0 6 Planar Implanted Passivated Silicon PIPS 0 8 0 2 1 2 0 6 or Silicon Charged Particle 2 8 0 6 Proportional Counter 0 8 0 2 1 2 0 6 or 2 8 0 6 Lithium Drifted Silicon Si Li
85. ount rate range The restorer can also be set to three manual settings SOFT MEDIUM and HARD These setting can be used with detectors having exceptionally stable baselines at all rates or with detectors which at high rates develop unusual noise requiring a some what lower restoration rate than provided by AUTO Rate The SOFT selection signifi cantly reduces the baseline restorer s restoration rate This may prove to be advantageous in some low count rate low energy applications With the SOFT se lected the restorer s low frequency noise suppression effectiveness is reduced The ambient low frequency noise and the implementation of noise reduction techniques re garding setup can easily be assessed and tested For situations where a higher than normal restoration rate is required the restorer rate may be set to MEDIUM or HARD which increases restoration rate proportionately This can improve performance at extremely high input counting rates or where more control is required to maintain the baseline such as with some NalI TI scintillation de tector systems Manual Fast Discriminator Threshold 92 In some cases you may want to set the Fast Discriminator threshold manually For best performance set the threshold just above the system noise level 1 Set the Amplifier Gain and shaping as required 2 Set the FDisc Mode in the Gain Device Adjust screen to Manual 3 Remove all excitation sources from the vicinity of the d
86. ower On LED and one of the High Voltage Range LEDs will remain on unless otherwise programmed by the host computer the DSA 2000 defaults to the 1 3 kV range In addition the Comm Tx and Comm Rx LEDs may flash indicating that communication with the host computer is taking place If the DSA 2000 detects a communications error with the host computer the Fault LED will remain illuminated This could result from a fault in the DSA 2000 hardware or a Ethernet communication problem with the network or host computer 4 User Interface and Controls This chapter provides basic information on the user interface and functional operation of the setup controls for the Model DSA 2000 Digital Spectrum Analyzer Additional details and discussion can be found in Chapter 6 Basic Spectroscopy Operation Chap ter 7 PUR LTC Operation and Appendix B Performance Adjustments Unless noted otherwise all controls are programmable through the host computer soft ware For specific details on using the host computer software please refer to the ap propriate software user s manual MID Wizard or MID Editor The first step in using your DSA 2000 is to let it know the number and types of MCAs that are installed in or connected to your system by way of an MCA Input Definition MID For most Genie 2000 based systems you ll want to use the MID Wizard to help you set up your DSA 2000 s Input Definition quickly and easily If your Input Definition is mor
87. p inhibit input BNC connector HV INH Logic low or ground inhibits the HV output AMP IN Detector Preamplifier signal input BNC connector PREAMP Provides power to standard detector preamplifier output 9 pin female D connector MONITOR Monitor output allows examination of sampled data recon structed in time serves as a user aid to assist with setup BNC connector ICR Incoming count rate output provides a standard TTL logic pulse frequency corresponds to the input count rate BNC connector GATE Gate signal input accepts positive logic pulse or de level for co incidence and anti coincidence gating BNC connector Internal Controls Precision Pulser Connectors LSP Reserved for control of future precision pulser MSP Reserved for control of future precision pulser MCS PHA Start Stop Connectors MCS IN MCS count input BNC connector MCS S S External MCS start stop input BNC connector PHA S S External PHA start stop input BNC connector Sample Changer Connectors RDY Sample Changer Ready input BNC connector ADV Sample Changer Advance output BNC connector Ethernet Connectors AUI Ethernet AUI output 15 pin female D connector 10Base2 Thin wire Ethernet output BNC connector Note The Ethernet station address for this unit is located near these connectors Diagnostic Connector Bidirectional RS 232 diagnostic port 9 pin male D connector Power Entry Module Power entry module with integral IEC 320 c
88. parameters are grouped into six device types MCA Sample Changer Stabilizer High Voltage Gain and Filter For this quick setup and check of the DSA 2000 many of the parameters may not require adjustment leave them set to the default values Parameters marked with an asterisk indicate factory default settings If the setup parameters were previously changed and saved using the MID File Save command the host computer will down load the last value s saved 6 MID Editor Settings Please verify or set the following setup parameters in your Genie Spectroscopy System s MCA Input Definition MID Editor For complete information on editing MID files refer to the MID Editor chapter in your Genie manual set 6a DSP Filter Gain Settings Preamp Type RC Inp Polarity Set Positive or Negative to match the preamp signal polarity of the intended detector 55 Inh Polarity Coinc mode 6b HV Settings Range Voltage Limit Voltage INH Signal Basic Spectroscopy Operation If the detector has an RC type preamp this function is not applicable and it is not necessary to make selections or changes If the detector has a reset preamp set Positive or Negative to match the polarity of the inhibit signal generated by the preamp The Canberra 2101 TRP and 2008 preamps produce a positive Inhibit signal Anti Sets the HV Range to match the high voltage requirements of the intended detector The choices are 5000 13
89. pe and resolution Detector Matching Scope Vert 50 mV div Horiz 10 us div Source Co 1 33 MeV peak at 6 V amplitude Count rate 2 kcps Shaping 5 6 us rise time 0 8 us flat top ail Somv amp M toys CRT 7 138mV Figure 41 Correct Pole Zero Compensation Scope Vert 50 mV div Horiz 10 us div Source Co 1 33 MeV peak at 6 V amplitude Count rate 2 kcps Shaping 5 6 us rise time 0 8 us flat top Figure 42 Undercompensated Pole Zero 63 64 Basic Spectroscopy Operation Scope Vert 50 mV div Horiz 10 us div Source Co 1 33 MeV peak at 6 V amplitude Count rate 2 kcps Shaping 5 6 us rise time 0 8 us flat top F T138mV Figure 43 Overcompensated Pole Zero Automatic Ballistic Deficit Correction In order to optimize performance with detectors of different sizes and varying charge collection times the DSA 2000 and DSA 2000A includes Automatic Ballistic Deficit Correction BDC Ballistic deficit occurs when the signal from a detector is passed through a filter whose shaping time is too short When this happens the filter is unable to completely process all of the charge collected by the associated detec tor preamplifier This can cause a deficit in the pulse height value which does not accurately represent the energy of the event Because the collection time of a detector can vary from one pulse to the next ballistic deficit may lead to loss of resolution an
90. pe overload For additional discussion on Pole Zero verification and manual adjustment refer to Manual Pole Zero Matching on page 61 Manual Pole Zero Matching At high count rates the Pole Zero P Z matching adjustment is extremely critical for maintaining good resolution and low peak shift For a precise and optimum setting of the P Z matching a scope vertical sensitivity of 50 mV div should be used With correct P Z spectral peaks will appear symmetrical while under compensated P Z will produce low energy tailing Over compensated P Z will produce high energy tailing An example of each condition is shown in Figure 40 With correct P Z spectral peaks will appear symmetrical Undercompensated P Z will produce low energy tailing Overcompensated P Z will produce high energy tailing Figure 40 Examples of Pole Zero Compensation 61 62 Basic Spectroscopy Operation Higher mV div scope settings sensitivity can also be used but this will result in a less precise P Z matching adjustment Most scopes will overload for a 10 V input sig nal and will exhibit overload aftereffects when the signal returns to the baseline Thus the P Z matching will be incorrectly adjusted resulting in a loss of resolution at high count rates To prevent scope overload and increase the P Z matching accuracy a clamping circuit such as the Canberra Model LB1502 Schottky Clamp Box should be connected at the scope input For additiona
91. pe triggering so that the positive trapezoid output is observed then set the square wave generator s amplitude control attenuator for an amplitude of 6 V 8 Change the scope vertical sensitivity to 50 mV div To prevent scope overload clamp the Monitor output signal by moving the LB 1502 Clamp Box switch to the CLAMP position Adjust the Pole Zero slider bar for correct pole zero compensation Figure 47 shows the correct P Z setting Figures 48 and 49 show over and under compensation for the preamplifier decay time constant As illustrated in Figure 47 the monitor output signal should have a clean re turn to the baseline with no bumps overshoots or undershoots Scope Horiz 20 mV div Vert 10 us div Figure 47 Correct Pole Zero Compensation 90 P Z Matching Using a Square Wave Generator Scope Horiz 20 mV div Vert 10 us div Figure 48 Overcompensated Pole Zero Scope Horiz 20 mV div Vert 10 us div Figure 49 Undercompensated Pole Zero 91 Performance Adjustments Baseline Restorer The digital baseline restorer in the Model DSA 2000 is flexible and allows adjustment for varying baseline conditions affected by detector type noise and count rate The baseline restorer rate is selected using the BLR mode drop down menu in the Filter Device Adjust screen With the Baseline set to AUTO the digital baseline restorer is automatically set for optimum performance throughout the usable input c
92. power cord before working on the unit Leaving the ac input power connected while working on the power entry module can result in serious injury or death Connecting to the Ethernet The following discussion will guide you in connecting your DSA 2000 Digital Spec trum Analyzer for communications over the Ethernet Figures 3 and 4 show typical Ethernet connections e Locate the desired Ethernet port on the DSA 2000 s rear panel Both 10Base2 and AUI connectors are available e Connect the appropriate cable Setup and Configuration Ethemet Tee Tranceiver Connector 10 Base 2 DSA 2000 DSA 2000 Figure 3 Multiple DSA 2000s in an Existing Network e Identify the unique Ethernet station address assigned to the DSA 2000 the four characters such as 07C6 on the label next to the Ethernet port Connecting to the Ethernet Each DSA 2000 is shipped with a 3 m 10 ft RG 58 U coax cable and a Tee connec tor for connecting to the Thinwire 10 base 2 network If the DSA 2000 is to be con nected directly to its host computer you need only the coax cable your system 50 ohm terminators and the Tee connector However if the DSA 2000 is going to be con nected in a network with other devices on the Ethernet you may need additional ca bles and connectors Note A BNC Tee connector and 3 m 10 ft RG 58 U coaxial cable are provided with the DSA 2000 The following hook up examples assumes using your sys tem 50
93. pplications LTC MODE ON Enables pileup rejector and live time corrector LTC LTC gener ates dead time to extend the acquisition time to compensate for events that are piled up and rejected OFF Pileup rejector and LTC disabled Filter RISE TIME 35 rise and fall times ranging from 0 4 us to 28 us step size dependent on rise time range may be viewed on the MONITOR output FLAT TOP 21 flat top time selections ranging from 0 to 3 us increment size de pendent on flat top range may be viewed on the MONITOR output BLR MODE AUTO The baseline restorer is automatically optimized as a function of the trapezoid shaping time and count rate HARD MEDIUM or SOFT Sets the baseline restorer to fixed rates POLE ZERO Displays the current Pole Zero setting value ranges from 0 to 4095 1 to 4095 represents 1 7 ms to 40 us a value of zero sets the pole zero compensation off or to infinity adjustment enabled when RC preamp type is selected increment decre ment value using the associated slider bar BDC Computer command to optimize the trapezoidal flat top parameters to match the charge collection time of the detector Auto P Z DSA 2000A only Available only for the DSA 2000A with automatic pole zero option installed Computer command initiates the automatic process PREAMP TYPE Selects the pole zero mode RC pole zero can be adjusted by com puter command range 40 us to infinity RESET Sets pole zero at infinity f
94. ptimized for resolution For this case the trapezoidal rise time parameter is increased so that the processing time and throughput are equivalent to Gaussian shaping Table B 1 lists the DSA 2000 Rise Time and Flat Top settings which optimize perfor mance for high throughput good resolution and optional setting for best resolu tion lower throughput when using Germanium Coaxial detectors Table B 1 Gaussian Shaping vs Throughput and Resolution Gaussian Highest Throughput Highest Resolution Shaping us Rise Time Flat Top Rise Time Flat Top 0 5 us 0 8 us 0 2 us 1 2us 0 2 us 1 0 us 1 2 us 0 6 us 2 8 us 0 6 us 2 us 2 8 us 0 6 us 5 6 us 0 6 us 4 us 5 6 us 0 8 us 12 us 0 8 us 6 us 8 8 us 1 2 us 18 4 us 1 2 us 12 us 16 8 us 2 4us 28 us 2 4 us Note 1 Optimized for high throughput good or equivalent Gaussian shaping resolution Note 2 Optimized for highest resolution equivalent Gaussian shaping processing time throughput 87 Rise Time and Flat Top Adjustments Table B 1 lists settings for optimizing throughput or resolution Of course a setting in between can be chosen to optimize performance for a specific application The Gaussi an Equivalent Shaping Times are suggested as starting values You may change these values to enhance throughput or resolution as required by your application As previously mentioned the shaping times recommended for highest thr
95. r Interface and Controls Loading Multiple Definitions Though you will usually use only one definition at a time there may be times when you want to load more than one definition To do this be sure that the Input name in each of the Definition Files is unique If you try to load an Input Definition which contains a duplicate Input name you ll see an error message telling you that the requested Definition can t be loaded Unloading the Database Though some of the programmable front end controls such as ADC Gain or Amplifier Gain are initially set with the MCA Input Definition Editor many may also be ad justed in the Acquisition and Analysis application while you re collecting data These adjustments can be stored in the database with File Save and when you Unload the database are saved in an Input Definition File for future sessions The Unload Process To unload a Database click on the Database menu s Unload from command which will bring up the Dialog Box shown in Figure 28 If several choices are listed there are multiple definitions in the database Unload Definition from Database File Name Figure 28 The Unload Dialog Click on the one you want to unload then click on the Unload from button Note that this menu item is disabled if the MCA Runtime Configuration Database is currently being used by another application 38 Acquisition Window Adjust Screen Acquisition Window Adjust Screen The fo
96. r Window Note that the phrase local Untitled in the title bar means that the MID Editor is con nected to the local VDM and that no file is currently open this is the default condition in a non networked environment Building an MCA Definition Building an MCA Definition means e Selecting the MCA and front end hardware to be used for each input through the Device Menu e Defining the operating characteristics and modes for each MCA and its front end hardware through the Settings Menu In this section we ll explain how to add and delete the MID editor s MCA entries and will explain what the definition entry consists of and the next section tells how to define the DSA 2000 MCAs 17 User Interface and Controls The remainder of this chapter discusses how the definition is saved to a disk file how a definition can be edited and how to use a definition by loading the file into the MCA Runtime Configuration Database Adding an MCA The Edit menu shown in Figure 10 is used to add MCA hardware to or delete MCA hardware from an MCA Input Definition Figure 10 The Edit Menu To add an MCA select the Add MCA command in the Edit menu to see the Add MCAs to Definition Table Dialog Box Figure 11 Figure 11 shows a typical Add MCA list box allowing you to add an DSA 2000 MCA to the MCA Definition Table You can add more DSA 2000 MCAs to the definition at any time with this command To add an MCA to your def
97. r rise time settings offer a better signal to noise S N ratio and longer flat top settings reduce the effects of ballistic deficit However as the system count rate increases resolution may degrade more rap idly due to increased processing time and the effects of pulse pile up Performance Adjustments For most Ge detector applications digital trapezoidal shaping provides Gaussian equivalent resolution with half the processing time Faster processing time means the DSA 2000 provides significantly greater throughput than a traditional analog system with its processing or shaping times set for equivalent resolution When using small Ge detectors which are optimized for high count rate performance throughputs of 100 kcps can be achieved To achieve 100 kcps and higher throughput the highest spectral peak must not exceed 80 of full scale For more information on count rate perfor mance refer to Canberra s Application Note Performance of Digital Signal Proces sors for Gamma Spectroscopy Please contact your sales representative to request a copy However the settings which realize reduced processing time high throughput and equivalent resolution for Ge detectors may be a bit aggressive for some low energy ap plications For these applications which include LEGe Si Li and X ray detectors resolution will be equal to or better than that obtained with traditional analog systems when the Rise Time and Flat Top filter parameters are o
98. rt 101 DSA 2000 Architecture eee 101 Initialization 4 5 AA AS a wd Oo Madd he e eR BabA A G 101 The DSA2000 s Initialization Sequence 0 00000 0000048 102 Installation Considerations 108 1 Introduction This manual is a comprehensive reference covering the capabilities and operation of the DSA 2000 Digital Signal Analyzer Introduction This chapter is an introduction to the manual s contents and an overview of the DSA s features Controls and Connectors You ll find a brief description of the front and rear panels indicators and connectors here Setup and Configuration Read this chapter for instructions on unpacking and setting up your system including how to connect it to an Ethernet User Interface and Controls This chapter tells you how to easily configure your system using the MID Wizard but also covers using the MID Editor for more complex configurations Using the Monitor Output The DSA s Monitor Output presents an analog signal representing the sampled digital filtered signal This chapter discusses how to use it in setting up the DSA 2000 and verifying system gain Setup and Operation This is the heart of the manual covering day to day basic spectroscopy operation pole zero matching your DSA 2000 to the detector for maximum resolution and ac quiring a spectrum PUR LTC Operation This chapter detail
99. s a large signal to the DSA 2000 driving it into severe overload The DSA 2000 automatically senses preamplifier reset events and gates off pulse processing during the associated overload event However to obtain optimum performance especially at high count rates it is recommended the preamplifier s Inhibit signal be connected to the Inhibit Input on the DSA 2000 Figure 50 shows Trapezoid Signal Preamp Output and Inhibit Signals Amp Out i en ee Output Reset inhibit Figure 50 Monitor Output TRP Output TRP Inhibit Operation with Reset Preamps The DSA 2000 system inhibit is initiated or derived from the preamp inhibit signal The optimum system inhibit time can be set automatically by the DSA 2000 or ad justed manually For automatic inhibit set the Inhibit Mode Gain Device Adjust screen to Reset When using the RESET mode of operation the correct system in hibit time is automatically set It is not necessary to make critical adjustments of the inhibit signal at the preamp However the preamp inhibit signal should be set to its minimum value Please consult the Detector Preamp Operator manual for this adjust ment Note When using the automatic RESET inhibit mode the system inhibit is the time interval automatically generated by the DSA 2000 OR the external inhibit duration which ever lasts longer For proper operation set the preamp inhibit time to minimum or it can override the optimum inhibit ti
100. s chapter is a quick setup guide and outlines the operation of the Model DSA 2000 Digital Spectrum Analyzer More detailed information about specific functions can be found in Chapters 2 through 5 Chapter 7 and the Appendices Following the proce dures below will make you familiar enough with the instrument to be able to use it ef fectively Initialization and Self Diagnostics at Power On When power is first applied to the Model 2000 it will go through an initialization and self diagnostics process During this initialization period indicated by the Power On LED blinking the DSA 2000 is running internal diagnostic routines to verify correct operation of the hardware These routines require 15 to 20 seconds to complete The front panel hardware is tested next with the front panel LEDs and bar graph displays turning on sequentially for approximately 2 to 5 seconds As the bar graph sequently illuminates each segment it will pause briefly at half scale If the diagnostics were successful and communication with the host computer is estab lished the Power On LED and one of the High Voltage Range LEDs will remain on unless otherwise programmed by the host computer the DSA 2000 defaults to the 1 3 kV range In addition the Comm Tx and Comm Rx LEDs may flash indicating that communication with the host computer is taking place If the DSA 2000 detects a hardware or communication error with the host computer the Fault LED will remain illu
101. s how and why you use the DSA 2000 s Pulse Pileup Rejector and Live Time Corrector PUR LTC feature which improves both measurement and anal ysis The Appendices The appendices offer useful information not usually needed in day to day operation Introduction The DSA 2000 Digital Spectrum Analyzer is a fully integrated high performance mul tichannel analyzer All of the subsystems required for high quality spectrum acquisi tion are integral to the unit digital signal processor DSP high voltage power supply HVPS digital stabilizer MCA memory and Ethernet network interface The instru ment is suitable for applications involving virtually all gamma and most X ray detec tor types The heart of the DSA 2000 is the Digital Signal Processor subsystem Unlike conven tional systems which digitize the detector preamplifier signals at the end of the signal processing chain the DSA 2000 digitizes the detector preamplifier signals at the front end of the signal processing chain This approach eliminates significant amounts of an alog circuitry at the front end of the instrument resulting in increased stability accu racy and reproducibility The signal processing subsystem in the DSA 2000 also includes automatic Ballistic Deficit Correction Auto BDC When an Auto BDC optimization is started the sys tem monitors the rise time of the incoming detector preamplifier pulses and automati cally adjusts the flat top setting to acco
102. sed for this particular entry in the table Input This is the name that will be used to refer to this specific hardware entry in the table The MID Editor automatically assigns these names sequentially as DETnn starting with nn 01 As we ll see in Input Name on page 33 you can easily change these names to something you find more meaningful Size This shows the number of data channels assigned to this input ADC This column displays the type of ADC associated with the DSA 2000 MXR The MXR column isn t used by the DSA 2000 Stab This column describes the Stabilizer associated with the DSA 2000 Amp This column describes the amplifier associated with the DSA 2000 HV This column describes the High Voltage Power Supply associated with the DSA 2000 Gain This column describes the DSP Gain device associated with the DSA 2000 Deleting an MCA If you change your mind and want to remove an MCA that you have added to the defi nition you can do it easily by Defining an MCA 1 Selecting the table entry you want to delete 2 Clicking on the Delete MCA command in the Edit menu to see the Dialog Box in Figure 13 Click on OK to remove the entry Delete MCA Delete the following MCA and its inputs Input Size ADC MXR Figure 13 The Delete MCA Dialog Defining an MCA This section discusses setting up a DSA 2000 MCA which has a fully programmable front end That is its DSP Gain DSP Filter Digital Sta
103. slightly before or after each of the main spectral peaks If you are using a Canberra Model 2101 preamplifier disable the Reset Delay using these three steps 1 Remove all signal and power connections from the preamp 2 Remove the preamp cover and change jumper plug W1 from position A to position B Jumper plug W1 is located on the main PC board next to RV1 3 When done reinstall the preamp cover and reconnect the preamp to the DSA 2000 as before or as indicated in Spectroscopy System Setup on page 53 and in Figure 39 on page 54 For additional information on the Reset Delay feature and jumper plug W1 please refer to the Model 2101 User s Manual 93 Performance Adjustments Pole Zero Setting for Reset Preamps Since the Reset Preamp output signal is a step function instead of the classical tail pulse with exponential decay Pole Zero compensation is not required For this appli cation the Pole Zero should be set off or to infinity On the DSA 2000 this is accom plished by setting the preamp type to RESET The preamp type can be changed in the Filter Device MID Editor If RESET is selected the Pole Zero is automatically set to a value of zero corresponding to a fall time of infinity and no further adjustment is re quired If RC is selected the pole zero value in the Filter Device Adjust screen must be manually set to zero Using the Reset Inhibit During the preamp reset interval the preamp reset event produce
104. ss Hex 1212 Cancel Help Figure 15 The MCA Device Setup Dialog Type of Input Select the DSA 2000 s input type here PHA MCS or Both Sample Changer This screen lets you set the polarity Normal or Inverted of the sample changer s Ad vance and Ready control signals The Settings The following section describes those parameters for the DSA 2000 that can be ac cessed from the MID Editor via the Settings menu Figure 16 23 24 User Interface and Controls MCA Sample Changer ADC MA Stabilizer ae ee Amplifier Ls High Voltage Power Mgmt ASC DSP Gain DSP Filter Figure 16 The Settings Menu MCA Settings The only setting you can change here is the Input Type PHA MCS or Both Stabilizer Settings The Stabilizer maintains the stability of high resolution spectroscopy in applications involving long count times or high count rates It accomplishes this by using reference peaks in the spectrum and correcting the ADC s conversion gain or its zero intercept or both to keep these peaks from drifting The count rates in these reference peaks should be high enough to be significantly more than the background in their chosen stabilizer windows Selecting the Stabilizer command pops up the Dialog Box shown in Figure 17 Note This window s initial focus is on the Cancel button pressing the keyboard s ENTER key after making changes in this dialog box will cancel
105. t only in this Dialog Box it cannot be changed in the Ac quisition and Analysis application Voltage Limit The Voltage limit control establishes the HVPS s maximum output voltage within the selected range It must be set before the Voltage control is adjusted This control can be set only in this Dialog Box it cannot be changed in the Acquisition and Analysis application Voltage After setting the Voltage Limit the Voltage scroll bar sets the output of the HVPS be tween the Voltage Limit s minimum and maximum settings The voltage can also be typed in from the keyboard then accepted with the Ok button within the control The Acquisition and Analysis application allows you to adjust the output voltage as well as turn the HVPS on and off and reset it Inh Signal Sets the pull up voltage of the HV INH connector to 5 or 12 V All Canberra detec tors and preamps use 5V DSP Gain Settings The DSP Gain settings screen Figure 20 for the DSA 2000 contains the following controls Coarse Gain Sets the device s coarse gain It s best to choose the highest Fine Gain which com bined with the Coarse and Super Fine Gains will produce the total desired gain Fine Gain Sets the device s Fine Gain multiplier S Fine Gain Sets the device s Super Fine Gain value Defining an MCA Coarse gain DSP Gain for input DETO1 Fine gain 1 6000 lt A 0 400 1 600 S fine gain 0 03 Coinc mode
106. t to 0 39 User Interface and Controls On enables gain stabilization allowing the Stabilizer to compare the incoming data to the gain Centroid and Window settings then compensate for data below or above the Centroid Hold disables gain stabilization but maintains the current correction adjustment at the Stabilizer s output Gain Ratio The Gain ratio value is interpreted by the stabilizer as the ratio to maintain between the two gain windows ratio upper window lower window For instance a value of 1 would be appropriate for a pure Gaussian peak Zero Centroid Sets the centroid in channels of the reference peak at the low end of the spectrum for zero intercept stabilization Zero Window Sets the width in channels of the upper and lower sampling windows on either side of the zero reference peak Zero Spacing Sets the spacing in channels between the upper and lower sampling windows The windows should be placed so that a shift in the reference peak reflects a significant change in count rate through the window For broad peaks the spacing should be set so that the windows edges are not on the flat part of the peak Zero Mode Sets the Zero Stabilization mode to Off On or Hold Off disables zero stabilization and sets the correction adjustment to 0 On enables zero stabilization allowing the Stabilizer to compare the incoming data to the zero Centroid and Window settings then compensate for data below
107. the LTC set OFF Set the LTC to OFF clear the memory and set acquire to ON Accumulate a spectrum with the LTC OFF Compare the two spectra LTC On and LTC Off overlapping them with the compare function as seen in Figure 44 The spectra shown in the comparison are for an ICR of 50 kcps and 4 us Gaussian Equivalent Processing Time Rise Time 5 6 us and Flat Top 0 8 us Note the reduction in magnitude of both the sum peaks and background counts Also note the improved resolution of the sum peaks The background reduction and improved resolution are directly indicative of the Pileup Rejector s capabilities since only sum peak pulses which are indeed 100 in coincidence are processed Live Time Correction With a Live Source With PUR OFF VE Soa SS i A ng With PUR ON Figure 44 Comparing Co Spectra with PUR On and Off Live Time Correction With a Live Source To compensate for events rejected due to pile up and processing time a system dead time is derived by the live time correction function The dead time signal controls the MCA Live Time clock which extends the acquisition time by the appropriate amount The accuracy of the Live Time Correction LTC deployed on both traditional analog electronic and the DSA 2000 Digital Spectrum Analyzer is dependent on the operation of the Fast Discriminator fast channel and the pulse evolution time or dead time of the shaped signal slow channel In the case
108. the changes Be sure to click on the OK key to accept the changes Defining an MCA Digital Stabilizer for input DETO1 Gain centroid Gain window Gain spacing Gain ratio 7680 ch 8 chs 64 chs 1 000 LT T Db AUO ETT I Pp fT P 10 16376 1 2 512 0 01 100 00 Zero centroid Zero window Zero spacing Zero ratio 8 chs 64 chs 1 000 ET K CITI P ELI P 10 16376 1 2 512 00 100 00 Gain rate div Zero rate div 1 CT P 1 512 1 Figure 17 The Stabilizer Settings Dialog Figure 18 shows the relationship between the Stabilizer s Centroid Window and win dow Spacing on a typical peak Spacing A MMMNN 7 Figure 18 The Relationship Between Stabilizer Functions 25 26 User Interface and Controls Gain Centroid Sets the centroid in channels of the reference peak at the high end of the spectrum for gain stabilization Gain Window Sets the width in channels of the upper and lower sampling windows on either side of the gain reference peak Gain Spacing Sets the spacing in channels between the upper and lower sampling windows The windows should be placed so that a shift in the reference peak reflects a significant change in count rate through the window For broad peaks the spacing should be set so that the windows edges are not on the flat part of the peak Gain Rate Div The Gain Rate Divisor sets the count rate dividers at the input to the correction register for Gain For high co
109. ting the Pole Zero please refer to Shaping Rise Time and Flat Top Adjustments on page 86 Using the Monitor Output to Verify System Gain The DSA 2000 gain settings are calibrated to produce the same system gain in keV channel as a traditional analog system with the same settings For a given detec tor radiation source and MCA setup conversion gain conversion range etc the re sultant MCA spectral peaks will be located in approximately the same MCA channel location for both the DSA 2000 and the traditional analog system The DSA 2000 gain factor can be verified using the Monitor Output However keep in mind the Monitor Output signal is reconstructed in the analog time domain and is only a visual aid to assist with setup and verify operation The Monitor Output is scaled to 8 volts full scale MCA collection as opposed to 10 volts for most traditional analog spectroscopy amplifiers This scale factor 10 8 must be taken into consider ation when verifying the DSA 2000 gain factor For example when the DSA 2000 Gain is set as follows Coarse Gain 120 Fine Gain x0 8337 SF Gain 0 0000e e The calculated gain is 120 x 0 8337 100 04 e The amplitude of the Monitor Output signal measures 4 volts The Input signal measures 0 05 volts 51 52 Using the Monitor Output e The DSA 2000 measured gain corrected for the 8 volt full scale range is 4 0 05 x 10 8 80 x 1 25 100 6 Basic Spectroscopy Operation Thi
110. tings The DSP Filter settings screen Figure 21 for the DSA 2000 contains the following controls BLR Mode Sets the baseline restorer mode With a setting of AUTO the baseline restorer is auto matically optimized as a function of trapezoid shaping time and count rate With set tings of SOFT MEDIUM and HARD the baseline restorer is set to fixed rates as selected 30 Defining an MCA DSP Filter for input DETO1 BLR mode Preamp type Flat Top Auto f RC Figure 21 The DSP Filter Settings Preamp Type Selects the Preamplifier type as either TRP Transistor Reset Preamp type or RC RC coupled preamp type RC enables the pole zero adjust screen in the MCA Ad just Filter Device screen TRP disables the pole zero adjustment This control can only be set via the MID Editor Rise Time Symmetrically sets the rise time and fall time of the digital filter time response As with conventional Gaussian shaping the degree of noise filtering is proportional to the rise time selection There are 35 rise fall times ranging from 0 4 to 28 us The rise time can also be set in the Acquisition and Analysis application for more information please refer to Rise Time and Flat Top Adjustments on page 86 Flat Top Sets the flat top portion of the digital filter time response The flat top matches the fil ter to the detector charge collection characteristics to minimize the effects of ballistic deficit There are 21 flat top time s
111. tive or negative signals from an associated detector preamplifier amplitude 10 V divided by the selected gain 12 V maximum rise time less than the selected flat top time setting decay time constant 40 us to infinity Zin Varies with Coarse Gain and Polarity settings from 500 to 2 KQ GATE Accepts a positive logic pulse or dc level high amplitude gt 2 5 V low am plitude lt 400 mV 0 to 7 V maximum de coupled open input allows PHA opera tion loading is 1 kQ to 5 V with Coincidence selected and 1 kQ to 0 V with Anticoincidence selected minimum pulse width 250 ns In COINC ANTI coinci dence mode a positive negative logic pulse or dc level during the rise time and flat top of the trapezoidal waveform will enable the conversion in process if the GATE is low high during this time the impending conversion will be disabled the recon structed trapezoidal waveform can be seen at the MONITOR output TRP INH Accepts a standard TTL logic signal functionality is dependent on which Inhibit Mode is selected NORM selected resets and inhibits the pileup rejector and extends the Dead Time signal for the duration of the INH signal RESET preamp se lected inhibits the DSA 2000 during the preamplifier reset cycle the leading edge of the INH signal resets the pileup rejector and allows the DSA 2000 to automatically disable pulse processing and extend the system dead time for the duration of the resul tant overload event The total in
112. to 3 0000e7 Offset Sets the devices digital offset in channels The digital offset shifts the memory assign ment of the device s conversions to the left e g an offset value of 4096 would shift channel 4096 down to correspond to channel zero of the memory LLD Sets the devices Lower Level Discriminator LLD as a percentage of the ADC s full scale 41 User Interface and Controls Zero Sets the device s zero intercept as a percentage of the device s full scale Conv Gain Sets the device s conversion gain It can be set from 256 to the maximum number of channels supported by the device The gain will change by a factor of two Note that this value is automatically copied down to the DSA 2000 s internal Conversion Range parameter FDisc Mode Sets the device s Fast Discriminator threshold mode AUTO allows the threshold to be optimized automatically above the system noise level MANUAL allows the threshold to be manually adjusted FDisc Setting Sets the device s Fast Discriminator threshold level when MANUAL Fdisc Mode is selected The range is 0 to 100 PUR Guard Sets the device s guard time GT multiplier to reject trailing edge pileup in the event of detector preamp anomalies The PUR guard sets the pileup reject interval which is defined by GT x TRisetime TFlattop LT Trim Allows adjustment of the trapezoid pulse evolution time or dead time to optimize LTC performance The adjustme
113. tomatic Ballistic Deficit Correction Acquiring a Spectrum PUR LTC Operation Pileup Rejection With a Live Source Live Time Correction With a Live Source 2 2 0 0 0 0 0 0 00 0000000800 ee ae PUR Guard Setup PUR Guard Adjustment Using a Live Spectrum Specifications Programmable Controls ee Programmable Settings ee Pileup Rejector Live Time Corrector Start Stop Sample Changer High Voltage Power Supply HVPS Environmental 67 67 69 71 73 74 75 75 76 77 78 79 80 80 81 81 82 82 83 83 84 84 84 85 Physical iento Eta deta eh eh eee ets o Seen he Ges 85 Ordering Information 2 2 a 85 Performance Adjustments 86 Rise Time and Flat Top Adjustments 2 2 0 0000002 0 eee eee 86 P Z Matching Using a Square Wave Generator o o e 89 Baseline Restoter s so eosa ai e a a ee a Te 92 Manual Fast Discriminator Threshold o o e e 92 Operation with Reset Preamps ee 93 Configuring the Preamp Reset Mode o e 93 Pole Zero Setting for Reset Preamps e 94 Using the Reset Inhibit o e 94 Voltage Selecione a a BT Changing the Voltage Selection o ee ee 97 US a ES a o A a bg 98 Replacing the Covert s te eo davela ei a a a ee Gas 99 Rack Mount Hardware 100 Using The Diagnostic Po
114. tween the two zero windows ratio upper window lower window For instance a value of 1 would be appropriate for a pure Gaussian peak Correction Rng Correction range 1 Ge or 10 Nal This control selects the Gain Correction range that can be provided to correct for drift Select 1 for a germanium detector or 10 for a sodium iodide detector This control can only be set via the MID Editor High Voltage Settings The High Voltage command shown in Figure 19 adjusts the High Voltage Power Supply HVPS High Voltage Supply for input DETO1 Range Voltage limit Voltage C 5000v Inh signal 1300 0v Ok 1300v D C 5000y 1300 Apply to All Cancel Figure 19 The High Voltage Settings Note This window initial focus is on the Cancel button pressing the keyboard s ENTER key after making changes in this dialog box will cancel the changes Be sure to click on the OK button to accept the changes 27 User Interface and Controls Range The Range control must be set before the Voltage Limit or Voltage Control is ad justed sets HV Power Supply s absolute voltage limit to positive 1300 volts for a so dium iodide or cadmium telluride detector or positive or negative 5000 volts for a detector requiring no more than 100 uA of bias current such as a germanium detector This automatically changes the upper value for the Voltage Limit and Voltage con trols This control can be se
115. umper at the AUI device In some cases the switch or jumper can be accessed with out removing the AUI s cover In others cases internal access to the AUI is re quired and the unit s operator manual should be consulted Both the AIM556A and DSA2000 modules require that the heartbeat opera tion be enabled in order to pass their internal loopback diagnostic whenever a AUI device is used If the heartbeat in the AUI is not present or enabled the internal self test cannot operate properly thereby making it impossible to au tomatically determine the attached medium The heartbeat is enabled automat ically in the internal transceiver to satisfy the condition when the module is used in 10Base2 Thinnet applications because no external AUI device is re quired For proper operation connect either Thinwire or AUL not both Existing Thinwire Connection 1 Connect a BNC Tee connector to the existing Thinwire coax cable 2 Attach the BNC Tee connector with Thinwire coax cable attached to each end to the 10 Base 2 connector on the DSA 2000 s rear panel Local Thinwire Connection To Host Computer 1 Attach a 50 ohm terminator to one side of a BNC Tee connector and one end of the 50 ohm coax cable to the other side 11 Setup and Configuration 2 You can either completely uncoil the cable or only as much is needed to reach the host computer 3 Attach the BNC Tee connector with coax cable and terminator attached to the 1
116. unt rate With the LTC set ON changes in the reference peak net area will be significantly reduced The Live Time corrector extends the collection time compensating for signal processing time and events rejected due to pileup Note Performance may vary and is dependent on factors such as spectrum energy distribution detector characteristics such as geometry size and detector bal listic deficit PUR Guard The PUR Guard Time GT function is provided to optimize the performance of the Pileup Rejector The pile up reject interval is defined as GT x Tr T pa Top Where GT PUR Guard Time selection 8 selections ranging from 1 1 to 2 5 are pro vided 71 72 PUR LTC Operation Tp Filter Rise Time selection Trtat Top Filter Flat Top selection With the default minimum PUR GT setting 1 1x the pile up reject interval and the Peaking Time are the same see Figure 45 Trapezoid Signal I e Peaking Time 1 1 Tr Trrat top Pile up Reject Interval l goer we I PUR Guard at X1 1 Pile up Reject Interval extended by PUR Guard gt X1 1 Figure 45 The PUR Reject Interval Subsequent events arriving within the PUR reject interval are rejected events occur ring afterwards are accepted Increasing the Guard Time extends the pile up rejection interval to protect subsequent events from being corrupted by anomalies associated with the tail of the previous event As expected throughput is reduced as the Guard time and
117. unt rate reference peaks increasing the Divider value will smooth out the correction applied to the system and minimize any peak broadening This con trol can only be set via the MID Editor Gain Ratio The Gain ratio value is interpreted by the stabilizer as the ratio to maintain between the two gain windows ratio upper window lower window For instance a value of 1 would be appropriate for a pure Gaussian peak Zero Centroid Sets the centroid in channels of the reference peak at the low end of the spectrum for zero intercept stabilization Zero Window Sets the width in channels of the upper and lower sampling windows on either side of the zero reference peak Zero Spacing Sets the spacing in channels between the upper and lower sampling windows The windows should be placed so that a shift in the reference peak reflects a significant change in count rate through the window For broad peaks the spacing should be set so that the windows edges are not on the flat part of the peak Defining an MCA Zero Rate Div The Zero Rate Divisor sets the count rate dividers at the input to the correction register for Zero intercept For high count rate reference peaks increasing the Divider value will smooth out the correction applied to the system and minimize any peak broaden ing This control can only be set via the MID Editor Zero Ratio The Zero ratio value is interpreted by the stabilizer as the ratio to maintain be
118. use or if the equipment is serviced or repaired or if an attempt is made to service or repair the equipment by other than our personnel without our prior approval Our warranty does not cover detector damage due to neutrons or heavy charged particles Failure of beryllium carbon composite or polymer windows or of windowless detectors caused by physical or chemical damage from the environment is not covered by warranty We are not responsible for damage sustained in transit You should examine shipments upon receipt for evidence of damage caused in transit If damage is found notify us and the carrier immediately Keep all packages materials and documents including the freight bill invoice and packing list Software License When purchasing our software you have purchased a license to use the software not the software itself Because title to the software remains with us you may not sell distribute or otherwise transfer the software This license allows you to use the software on only one computer at a time You must get our written permission for any exception to this limited license BACKUP COPIES Our software is protected by United States Copyright Law and by International Copyright Treaties You have our express permission to make one archival copy of the software for backup protection You may not copy our software or any part of it for any other purpose Revised 01 00

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