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DSA-1000 Hardware Manual

1. 18 MID editor MID wizard 2 2 ee e 13 MID wizard sos sasa wy ia ee ee 13 O t of SErVICS nb ee a ih E 27 Polarity High voltage control 91 Pole Zero Assistant 34 Pole Zero matching 49 Power Adapter so 04 a oly RIG Se 9 USNS AC fog pope ee Be we Bape eed ee 9 Range High voltage control 21 30 92 Settings High voltage 20 30 MPU Se soe ita Gros ee 26 Stabilizer 52 bes we ee eR eae S 18 Stabilizer Settings 18 System grounding 10 Voltage control high voltage 21 30 Voltage limit high voltage control 21 101 102 Notes A CANBERRA Warranty Canberra we us our warrants to the customer you your that for a period of ninety 90 days from the date of shipment software provided by us in connection with equipment manufactured by us shall operate in accordance with applicable specifications when used with equipment manufactured by us and that the media on which the software is provided shall be free from defects We also warrant that A equipment manufactured by us shall be free from defects in materials and workmanship for a period of one 1 year from the date of shipment of such equipment and B services performed by us in connection with such equipment such as site supervision and installation services relating to the equipment shall be free from defects for a peri
2. coca us Figure 4 Defining the Full Memory and Device Serial Number for USB Operation Note Memory size of 8k and 16k are selectable for PHA acquisition mode and 8k only for the MCS acquisition mode RS 232 Interface For the RS 232 Interface the setup screen will ask you to define the MCA Full Mem ory COM Port and Baud Rate as shown in Figure 5 Note Memory size of 8K and 16K are selectable for the PHA acquisition mode and 8K only for the MCS acquisition Mode 14 The MID Wizard MID Setup Wizard Step 2 Figure 5 Defining the MCA Full Memory COM Port and Baud Rate for RS 232 Click on the COM Port Box to select the desired COM port and Baud Rate box to se lect the baud rate The DSA 1000 supports baud rates of 2400 4800 9600 19200 38400 57600 and 115200 as shown in Figure 6 MID Setup Wizard Step 2 Figure 6 Setting the Baud Rate for RS 232 Operation 15 User Interface and Controls Note Baud rates higher than 57 kbaud may require the use of special hardware and or device drivers installed in your computer 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 1000 Step 5 The Step 5 screen in Figure 7 asks you to define the high voltage power supply s Range Voltage Limit and Voltage Click on the Range Box to select the desired volt age range The DSA 1000 supports four voltages ranges 5000 V dc 1300 V dc 5000 V de
3. 5 5 V HV INH Accepts input from the detector preamplifier to shut down the HVPS in the event of a detector warm up polarity is user selectable to match the preamplifier rear panel BNC connector Positive polarity for all Canberra preamplifiers Enable condi tion cold detector is an open circuit or active high gt 1 2 V to 24 V Inhibit condi tion warm detector is 24 V to lt 1 2 V or ground Negative polarity for all preamplifiers and LN monitors where enable condition cold detector is 24 V to lt 1 2 V Inhibit condition warm detector is open circuit or active high gt 1 2 V to 24 V With Negative selected an open input will disable the high voltage MCS MCS counts input TTL compatible maximum rate lt 1 MHz minimum pulse width 220 ns logic low lt 0 8 V logic high 2 2 V rear panel BNC connector DC PWR DC power input from supplied ac adapter 2 5 5 5 mm rear panel connec tor Nominal 7 5 V dc at 0 75 amps HV Dual range and polarity high voltage power supply voltage range and polarity selected by programming modules 10 to 1300 V de or 1300 to 5000 V dc rear panel SHV connector Low end of the 5000 V range is limited to 1300 V by software RS 232 RS 232 interfaces to host personal computer software selectable baud rate 2 4K to 115K supported rear panel 9 pin male D connector 63 Specifications USB High Speed USB interface for host communication rear panel USB Series B c
4. In this case the spectral 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 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 T y in Figure 29 The required guard time is determined by dividing T by the Peaking Time 1 Tas Top For example e The filter rise time is set to 5 6 us and the flat top is set to 0 8 us e 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 eve
5. Viewing the Trapezoidally Filtered Detector Pulses Figure 24 shows a display of the waveform produced by a Co source at an input count rate of 1 5k counts second For this example the DSA 1000 FILTER settings of 5 6 us Rise Time and 0 8 us Flat Top were used System gain was set so the Co 1332 keV energy peak collected at approximately 90 of full scale The scope is set to the default settings Using the Digital Oscilloscope to Verify System Setup 40 The digital oscilloscope can be used in setting up and verifying the Filter Shaping se lections Rise Time and Flat Top Pole Zero Gain and Input Polarity For informa tion on performing Pole Zero adjustment using the digital oscilloscope see Pole Zero Matching Using the Digital Oscilloscope on page 75 and also Appendix B Perfor mance Adjustment For information on optimizing the DSA 1000 adjustments when a Reset Preamplifier is connected refer to Operation with Reset Preamps on page 81 Note that unlike traditional laboratory oscilloscopes the DSA 1000 always presents one trace at a time for viewing When the Smoothing Factor is set to 2 or greater the waveform may represent the average of several pulses of varying amplitudes When high smoothing factors are selected the waveforms will fluctuate less and the pulse height will be roughly proportional to the center of mass of the MCA spectrum which depends on system gain This differs from traditional analog oscilloscope
6. 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 selections ranging from 0 to 3 Us The MCA Input Definition Editor FDisc Shaping Selects Normal or Low energy to optimize the fast discriminator shaping for the detec tor type Selecting NORMAL optimizes the fast discriminator shaping for use with Ge detectors and general gamma spectroscopy the fast discriminator filter rise time is set to 0 04 us Selecting Low energy the fast discriminator rise time is set proportional to the slow shaper rise time selection For this selection the fast discriminator shaping time increases proportionally with the slow shaper which optimizes the signal to noise ratio for improved pile up detection at low energies when using low noise low energy detectors MCS Settings If you choose the MCS mode in the Device MCA setup you II also have to select the MCS Disc Mode and Dwell time as shown in Figure 14 MCS for input DETO1 Figure 14 Choosing the MCS Disc Mode 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 Disc Mode The Disc Mode control establishes the MCS mode to be used Selecting Integral en ables the
7. LED indicators For more de tailed information refer to Appendix A Specifications DSAI000 rivas C vam 0 kV FS 0 100 13 CO O HV ON a 50 O IRC COMMC Aca CA L Pcaneeea J eee AAA Q z AAA Figure 1 DSA 1000 Front Panel Power Green LED indicates that the DSA 1000 is switched on and power is applied to the unit The Status Indicators The DSA 1000 s front panel indicators show the status of communication with host computer system diagnostics incoming count rate acquisition detector high voltage power supply and system power FAULT Yellow LED indicates a power ON diagnostic or high voltage fault has occurred HV ON Green LED indicates high voltage power status Constant ON in dicates the detector high voltage power supply is on and high voltage could be present at the rear panel high voltage connector Blinks for fault condition such as a high voltage overload or in hibit due to a detector warmup when connected HV LEVEL Green 10 segment bar graph indicates HV setting Rear Panel HIGH VOLTAGE Range and Polarity Four green LEDs indicating the selected HV range and polarity DEAD TIME Green 10 segment bar graph indicates Deadtime ICR Green LED indicates incoming count rate blink rate is propor tional to count rate COMM Green LED indicates USB or RS 232 activity ACQ Green LED indicates when data acquisition is active Rear Panel This is a brief descri
8. additional informa tion on configuring the High Voltage Settings in the MID Definition please reference page 20 For complete information on the MID Files and the Gamma Acquisition and Analysis window please reference the Genie 2000 Operations manual WARNING The DSA 1000 High Voltage Power Supply produces hazardous and lethal voltages Turn the DSA 1000 High Voltage Power Supply to OFF and main power to OFF before attempting to change the high voltage programming modules CAUTION Excessive voltage and or incorrect polarity can permanently damage the detector system It is recommended that the high voltage setting be verified prior to turning the high voltage power supply to ON HVPS Polarity and Range Configuration HVPS Polarity and Range Configuration Accessing the High Voltage Programming Modules To access the High Voltage Programming Module the following steps are performed 1 Remove the DSA 1000 front panel assembly turn the front panel thumb screws counter clockwise to remove the front panel see Figures 39 and 40 The screws are installed finger tight and should turn easily without the requirement for tools Its best to remove both screws simultaneously set the front panel aside Figure 39 Removal of the Front Panel 89 Configuring the High Voltage Power Supply Figure 40 Front Panel Removed 2 Slide the top cover forward to expose the high voltage Interlock board as shown in Figure 41 The top cover slid
9. and Appendix D Configuring the High Volt age Power Supply for configuring the HVPS range and polar ity Set the HVPS to ON the ON OFF control is located in the Status Box The High voltage output will increase to the set voltage at a con trolled ramp up rate Stabilizer Device Adjust Screen Gain Mode OFF 47 Basic Spectroscopy Operation Detector Matching 48 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 recovery due to high energy and cosmic events The Pole Zero adjustment range accommodates RC preamp fall times of 45 us to 1 7 ms When a reset preamp is used Pole Zero compensation is not required and the Pole Zero value must be set to zero 0 If the DSA 1000 is connected to a detector with a reset preamp such as the Canberra 2101 or 2008 use the MID Editor to change the preamp type in the MID Definition from RC to TRP With TRP selected the pole zero compensation is automatically set to a value of zero representing the matching required for a fall time of infinite duration which requires no compensation In this case the Pole Zero Assistant is not needed and will not be displayed If the preamplifier type selected in the MID Definition is RC and the DSA 1000 is connected to a reset preamp the P Z setting must be manually set to a value of zero 0 Please refer to the section Operation
10. and adjusting the digital oscilloscope Because the oscilloscope uses digital data overload does not occur and a high vertical sensitivity can be used to view and correct small overshoots and undershoots in the trapezoid waveform For the pole zero adjustment steps below an oscilloscope vertical sensitivity of 25 mV division is used With correct P Z adjustment spectral peaks will appear symmetrical while undercompensated P Z adjustment will produce low energy tailing Overcompensated P Z adjustment will produce high energy tailing An example of each condition is shown in Figure 30 TO Performance Adjustments 76 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 30 Pole Zero Compensation Examples Using a Ge Detector Co Source and Digital Oscilloscope Follow the steps below to optimize the Pole Zero using the Digital Oscilloscope Adjust the radiation source count rate to be between 500 counts second and 4k counts second Observe the trapezoidal waveform on the digital oscilloscope Verify that the preamp type in the MID Definition Settings DSP Filter screen is set to RC Adjust the Pole Zero slider bar located on the MCA Adjust Filter dialog second page so that the trailing edge of the trapezoid pulse returns to the baseline with no overshoots or undershoots The Digital Os
11. at 0 75 amps Preamp power 9 pin female D connector Pin Signal 1 2 AGND PISRPWR 12 V de THERM 24 V de 24 V de 12 Vdc VD AN Dn A Q Pin 3 carries 7 5 V dc Do notuse an Oxford preamp power cable because the voltage present at pin 3 may damage an Oxford preamplifier This problem is avoided by using a Canberra preamp power cable C1402 x or equivalent For information on maximum preamp current and power please refer to Appendix A Specifications Unpacking the DSA 1000 3 Getting Started Basic Hardware Setup and Configuration This chapter is a guide to unpacking and connecting the system Software installation is covered in Appendix A Software Installation of the Genie 2000 Operations Manual Unpacking the DSA 1000 When you receive your DSA 1000 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 1000 desktop Digital Spectroscopy Workstation e This manual e One ac adapter e One ac adapter line cord e One 3 m 10 ft RS 232 serial interface cable e One 3 m 10 ft USB computer cable System Options e S502C 500C Genie 2000 Basic Spectroscopy Software V2 0A or later required Complete System If you ordered a complete system it will consist of all
12. before restoring power With exception to the High Voltage programming modules as discussed in Appendix E Configuring the High Voltage Power Supply there are no internal adjustments or maintenance required 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 100 Index A AC power USIOB Adapter power C Changing the input sname D Digital Oscilloscope Controls and indicators Hiding from view LeaUnCMine bs ee ae Be a Be e Minimizing scope window Verifying system setup G Grounding the system H High voltage Changing the polarity Ranges a ds RS 21 30 setting thes g 24 eves bee ad 6 SEINES prada reci Voltage control 21 Voltage imit Host computer Connecting 10 ksa reo Connecting using the RS 232 port 9 Connecting using the USB port 10 Input Name changing Out of Service o oo ES A A ee oot Input setings s s p a o o e Input size setting the M MCA input definition MID Wizard soe spse Gee pia m ea 91 30 MCA Input definition editor See MID editor MCA Settings
13. 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 80 The following steps will demonstrate the operation of the Pileup Rejector and its abil ity to reduce spectral interference 1 Connect the DSA 1000 and set it up as described in Spectroscopy System Setup on page 42 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 6001 SF Gain 1 00 Leave the remaining functions as previously set up Verify that the LTC mode is set on the function is located on the Gain Device Adjust screen 55 PUR LTC Operation 56 Note 3 10 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 is not necessary to do it again If for some reason readjustment is necessary please refer to Detector Matching on page 48 Adjust the DSA 1000 Gain to locate the 122 keV Co 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
14. engaged in the connector sockets on the HV board Note When installing the HV Interlock board do not allow the board to rotate or twist as this might damage the wedge if equipped contact pins Reinstalling the Top Cover and Front Panel To reinstall the top cover and front panel the following steps are performed 1 Carefully slide the top cover back on toward the rear until it engages with the rear bezel 2 Carefully align the front panel and attach using the two thumbscrews Do not over tighten the front panel thumbscrews do not use a screwdriver they only need to be finger tight 94 Genie 2000 Software Configuration Genie 2000 Software Configuration The MID Definition may need to be configured to match the high voltage hardware setting If the MID definition and hardware configuration for the high voltage power supply do not match Genie 2000 will report a hardware verification error when at tempting to open the data source in the Acquisition and Analysis window For addi tional information on configuring the High Voltage Settings in the MID Definition please refer to page 20 High Voltage Plug in Module Part Numbers For part number information please refer to Appendix C Accessory and Cable Part Numbers 95 Connecting to the Host Computer 96 E Connecting to the Host Computer The DSA 1000 can be connected to the host computer using the RS232 serial commu nication interface or the high speed USB Universal Se
15. is open and or minimized and the following conditions occur e ICR is between 40 cps and 20 kcps e Digital oscilloscope Horizontal Scale us div is set too long resulting in a high rejection rate due to excessive pileup For additional 52 Detector Matching information on the scope pileup rejector please reference Scope Triggering and Pileup Rejector on page 41 for additional information The corrective action would be to reduce the ICR reduce the Scope Horizontal Scale setting or close the scope utility 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 cover a time constant range of 1 7 ms to 45 us When the value 0 is set no compensation is applied This is the proper setting for reset preamps and may be used if RC is selected as the preamp type instead of RESET in the MID Definition There are several ways to change the Pole Zero setting You can click on the scroll arrow buttons at each end of the slider bar click on the scroll bar between the slider box and the left right arrow buttons or click on the slider box button and drag to the desired value Clicking on the left right arrow buttons increments the Pole Zero setting one adjustment step at a time Clicking on the scroll box region between the slider box and the left right arrow buttons changes the Pole Zero setting by
16. of infinite duration which requires no compensation As a result it s not necessary to adjust the pole zero setting the Pole Zero Assistant screen is not required and is not displayed For this case the digital os cilloscope icon can be added to the main toolbar by choosing the Commands tab on the Display Preferences Toolbar Setup screen Choose the MCA Category icon group and drag the oscilloscope icon to the toolbar This pushbutton will now be avail able for starting the digital oscilloscope To remove the colored title bar just above the icon click in the colored area with the left mouse button and drag it down The toolbar can now be saved by pressing the Save button on the Display Preferences screen For more information on adding command buttons to the toolbar see Toolbar Setup in the Genie 2000 Spectroscopy System Operations Manual in the Display Preference sec tion of the Gamma Acquisition and Analysis section Minimizing or Hiding the Scope From View Note The Digital Oscilloscope update rate may be impacted by having MCA Ac quire set ON For best speed performance it is recommended the MCA Ac quire be set off when using the Digital Oscilloscope utility Minimizing or Hiding the Scope From View Each time the Digital Oscilloscope is opened its controls are set to the default settings This may be inconvenient if you are using a specific scope setup and you need to switch between various Adjust screen and the scope during the
17. of the items in the Basic System plus a computer All software will have been installed on the computer and the system will have been configured and tested at the factory Getting Started Basic Hardware Setup and Configuration Initial Setup To properly install and apply power to the DSA 1000 Digital Spectroscopy Workstation please verify the following Operating Environment Be sure you are in the operating environment specified for the instrument The temper ature and humidity specifications can be found in Appendix A Specifications High Voltage Power Supply Configuration Please consider and or verify the high voltage range and polarity requirements for the intended detector application at this time Turning the high voltage power supply ON or OFF and setting the output voltage set ting are programmable through the computer and Genie 2000 software environment However the polarity and range are manually configured using programming mod ules the programming modules are conveniently located inside the DSA 1000 The high voltage range and polarity are preset at the factory for the positive 5000 volt range which is compatible with many Ge detector applications If your detector re quires negative polarity or the higher current 1300 volt range please reference Appen dix D Configuring the High Voltage Power Supply for instructions on changing the DSA 1000 s high voltage range and polarity Please consult your detector s manu
18. or Appendix A Specifications for instructions for matching the polarity selection to the 43 Basic Spectroscopy Operation 44 Note intended detector preamplifier All Canberra detector preamps use the Positive polarity setting Turn on the DSA 1000 At power up the DSA 1000 will go through an initialization and self diagnostic process as described in Initialization and Self Diagnostics on page 11 The setup instructions that follow will allow you to get the DSA 1000 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 mV MeV and a Co radioactive source will acquire in channel 6500 to 7200 on the MCA when setup for a 8192 memory or spectrum size The programmable parameters are grouped into five Adjust Screen types Stab HVPS MCS Gain and Filter The MCS Adjust Screen is only available if the MCS acquisition mode is se lected in the MID Definition otherwise the MCS select button and Adjust Screen are hidden from view For information on setting the acquisition Mode in the MID Definition please reference MCS Settings on page 25 For this quick setup and check of the DSA 1000 many of the parameters may not require adjustment leave them set to the default values Parameters marked with an asterisk indicate initial factory default settings If the setup parameters were previously changed and saved using the MID F
19. 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 en ergy 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 Shorter shaping times such as 2 8 us rise time and 0 6 us flat top may degrade low count rate resolution performance slightly but re sults in less resolution 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 longer 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 Rise Time and Flat Top Adjustments For most Ge detector applications digital trapezoidal shaping provides Gaussian equivalent resolution with half the processing time Faster processing time means the DSA 1000 provides significantly greater throughput than a
20. the installation of the Genie 2000 software the user interface and operation of the setup controls for the Model DSA 1000 Desktop Spectroscopy Workstation Additional details and discussion can be found in Chapter 6 Basic Spectroscopy Operation Chapter 7 PUR LTC Operation and Ap pendix B Performance Adjustments With exception to the High Voltage Power Supply range and polarity configuration all controls are programmable through the host computer software For specific details on using the host computer software please refer to software documentation provided with the Genie 2000 V1 4 and higher installation CD For information on config uring the High Voltage Power Supply refer to Appendix D Configuring the High Voltage Power Supply Software and USB Driver Installation If your system wasn t integrated by Canberra please follow the instructions on the Ge nie 2000 installation CD to install the Genie 2000 software and purchased options If you plan to interface the DSA 1000 to the host computer using the USB port you need to first install the USB driver If this has not already been done please follow the directions below for setting up the USB driver under Windows 98 1 Connect the DSA 1000 to the host computer using the USB ports and the supplied USB cable Please reference Connecting the USB Cable on page 10 and Using the USB Port on page 98 for additional information 2 Turn the DSA 1000 power to ON 3 Window
21. to 5 kcps The 1173 2 keV Co reference peak should be at approximately 80 of the spectral full scale range If necessary adjust the DSA 1000 gain to properly locate the peak Once in place the source should not be moved or altered in any way for the re mainder of the experiment Clear the MCA and acquire a spectrum for 500 live seconds Record the net area of the 1173 2 keV Co peak source A To the Co source add approximately 25 kcps of Cs to make the total incoming rate 30 kcps Clear the MCA Collect a new spectrum for 500 live seconds and record the net area of source A Compare the net area of the 1173 2 keV Co peak acquired in step 6 and compute the percentage change 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 500 PUR Guard 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 decrease the system dead time and counts in the reference peak area at high count rates Likewise increasing the LT Trim will increase the system dea
22. to choose the highest Fine Gain which com bined with the Coarse and Super Fine Gains will produce the total desired gain The Coarse Gain allows selection of x2 5 through x1280 Fine Gain Sets the device s Fine Gain multiplier the adjustment range is x0 900 to x1 900 S Fine Gain Sets the device s Super Fine Gain multiplier the adjustment range is x0 9975 to x1 0025 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 Thattop For additional information on using the PUR Guard feature please refer to PUR Guard on page 59 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 O to 100 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 32 Acquisition Window Adjust Dialogs LT Trim Allows adjustment of the trapezoid pulse evolution time or dead time to optimize LTC performance The adjustment range is 0 to 1000 the default value of 500 p
23. us Rise Time and 0 6 us Flat Top were used System Gain was set so the Co 1332 keV energy peak collected in approximately 70 of full scale Baseline Restorer The digital baseline restorer in the DSA 1000 is flexible and allows adjustment for varying baseline conditions affected by detector type noise and count rate The base line 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 count rate range The restorer can also be set to three manual settings SOFT MEDIUM and HARD These setting can be used to manually optimize the BLR response for a specific detec tor and count rate application or system noise condition 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 cont
24. verses spectral size and incoming count rate For the measurements in Table 2 the Genie 2000 was running on a PentiumPro 200 MHz computer the RS 232 baud rate was set to 57 6 kbaud the Acquire mode was PHA and a Nal detector and Co source was used as the input source Table 2 Performance Comparison of RS 232 and USB DSA 1000 Configuration ICR 0 cps ICR 6300 cps RS 232 at 16K channels 1 11 sec 2 55 sec RS 232 at 8k channels 0 62 sec 1 39 sec USB at 16K channels 0 95 sec 1 19 sec USB at 8k channels 0 56 sec 0 70 sec Though the DSA 1000 is capable of serial communications at up to 115 kbaud most notebook computers don t work well at such fast data transfer rates In addition most notebooks have a smaller communication buffer which means that even if capable of a high baud rate they will slow down dramatically if asked to communicate with an other device such as a printer while the DSA 1000 is acquiring data Interestingly trying to run at a rate that is too fast actually slows the system down This is because the communications circuitry is not keeping up drops characters er rors are generated and the system retries The repeated retries consume considerable CPU resources Under these circumstances a system that may update the screen in 2 1 2 seconds at 19 2 kbaud may slow down to 10 20 seconds at 57 kbaud or in ex treme cases may lose communications entirely You c
25. vertical sensitivity of the digital oscilloscope in volts div This may be ad justed from 0 005 to 2 volts div The full scale reference is 10 V representing the height of a pulse which collects in the highest MCA channel Vertical Offset Adjusts the vertical position for viewing different portions of the waveform without changing the vertical scale 37 Using the Digital Oscilloscope Function 38 m Vertical Scale m Display Options 2 1 TF Zoom On volts M Grid Lines 0 005 Vertical Offset Trigger Select e Fast Discriminator LT Smoothing Factor Horizontal Scale Horizontal Delay Foo man y Defaults 100 0 5 microseconds div microseconds Figure 24 Digital Oscilloscope Screen Showing Detector Trapezoid Waveform Smoothing Factor Allows averaging up to 32 pulse waveforms to reduce noise Selection of 1 turns av eraging off Horizontal Scale Sets the horizontal time scale in microsecond div and the duration of the viewable por tion of the waveform Adjustable from 0 5 to 100 microsecond div Horizontal Delay Positions the waveform horizontally without changing the horizontal scale Delay is adjustable from 0 to 32 microseconds Display Options Zoom On Allows magnification of a small portion of the waveform To use the Zoom mode first check the Zoom On box Then press the left mouse button and drag the magnifying glass icon over the portion of the waveform of interest To le
26. 000 s s osos o e o 98 USB Standard Class and Cable Information 0 000000084 99 F Installation Considerations lt 100 INGEN se a a ee Oe eS ee Se AR a 101 1 Introduction The DSA 1000 is a full featured 16K channel integrated Multichannel Analyzer based on advanced digital signal processing techniques DSP When paired with the com puter of choice the DSA 1000 becomes a complete spectroscopy workstation capable of highest quality acquisition and analysis The instrument interfaces to all existing de tector technologies like HPGe Nal Si Li CAT or Cd Zn Te In many laboratories today spectroscopists are finding themselves constrained both in terms of available funds and physical space The DSA 1000 offers cost effective no compromise DSP quality spectroscopy in a very compact package The DSA 1000 is operated through the Genie 2000 spectroscopy software which pro vides the user with ultimate flexibility A wide range of application specific software options are available under the Genie 2000 family The excellent performance of the DSA 1000 derives from the application of DSP tech nology Earlier analog spectroscopy systems were prone to count rate and environmen tal instabilities that required continual adjustment of the signal processing subsystem and often compromised analysis results With the DSA 1000 these problems are dra matically reduced without bulky packages o
27. 2 Figure 33 Overcompensated Pole Zero For the examples in Figures 31 through 33 the DSA 1000 Filter settings of 5 6 us Rise Time and 0 8 us Flat Top were used System Gain was set so the Co 1332 keV energy peak collected in approximately 90 of full scale Adjustment Tips 1 When beginning the pole zero adjustment its best to start off with a high Vertical Scale setting such as 0 250 volts div Increase the vertical sensitivity lower Vertical Scale setting as you approach and get close to the desire optimal pole zero adjustment 2 Try setting the Smoothing Factor to a lower value when using Rise Time settings longer than 20 us Using a Nal TI Detector Co Source and Digital Oscilloscope When adjusting the pole zero matching using an Nal T1 detector follow the steps 1 and 2 from Using a Ge Detector Co Source and the Digital Oscilloscope on page 76 Due to AC coupling between the photomultiplier tube and the detector preamplifier signals from Nal T1 detectors often contain a second time constant which causes undershoot and a delay in the return to baseline after each pulse This coupling time constant cannot be removed using the pole zero compensation but with proper adjustment the main preamplifier time constant can be removed and the overall return to the baseline can be adjusted for minimal overshoot and undershoot Figure 34 shows the correct setting of the P Z adjustment for a typical Nal Tl detector wi
28. 2 4 4 8 9 6 14 4 19 2 28 8 38 4 57 6 and 115 2 kbaud can be selected the DSA 1000 automatically senses the baud rate setup at the host computer Note Baud rates higher than 57 kbaud may require the use of special hardware and or device drivers installed in your computer Low baud rate selections may degrade performance such as Genie 2000 command re sponse time spectral and digital scope display update rates For best performance se lect the highest baud rate supported by the host computer For slower computers that cannot keep up with a selected baud rate communication retries may begin to occur which will also degrade performance If this is suspected try using a lower baud rate and check for an improvement in performance Note The power management on some Lap Top computers may power down the RS 232 port which will disrupt the serial data stream the DSA 1000 If you ex perience random or periodic communication errors this may be due to the Lap Top computer power manager For this case it is recommended to disable the Power Management Features on your Lap Top computer Please consult the User Manual for your Lap Top computer for specific instructions to disable the Power Management Feature 97 Connecting to the Host Computer Connecting Multiple DSA 1000 s If you have more than one DSA 1000 each one will have to be connected to a differ ent COM port such as COM1 and COM2 Each DSA 1000 must be assigned to the COM port tha
29. A 1000 or adjusted manually using the adjustments located on the fourth page of the MCA Adjust Gain screen in the Acquisition and Analysis window Automatic Inhibit Mode For automatic inhibit set the Inhibit Mode to Auto this is the default setting When using the Auto mode the correct system inhibit time is automatically set It is not nec essary to make critical adjustments of the inhibit signal at the preamp However if the reset preamp is equipped with an adjustable inhibit signal pulse width it should be set to its minimum value Please consult the Detector Preamp Operator s manual for this adjustment Note When using the Automatic Reset inhibit mode the total system inhibit dura tion is the time interval automatically generated by the DSA 1000 OR the external preamp inhibit duration whichever lasts longer For proper auto matic operation set the preamp inhibit time to minimum or it can override the optimum inhibit time generated by the DSA 1000 Manual Inhibit Mode The Inhibit time can also be set manually by changing either the DSA 1000 Inhibit Setting adjustment or the inhibit pulse width adjustment on the preamp For certain de tector characteristics and applications it may be necessary to set the Inhibit time inter val longer then provided by the Automatic mode Manual adjustment may be necessary if the preamp signal contains extra time constants resulting in abnormal be havior which extends the overload r
30. DSA 1000 Digital Spectrum Analyzer Hardware Manual 9233800D ISO 9001 SYSTEM C E CERTIFIED Copyright 2005 Canberra Industries Inc All rights reserved The material in this document including all information pictures graphics and text is the property of Canberra Industries Inc and is protected by U S copyright laws and international copyright conventions Canberra expressly grants the purchaser of this product the right to copy any material in this document for the purchaser s own use including as part of a submission to regulatory or legal authorities pursuant to the purchaser s legitimate business needs No material in this document may be copied by any third party or used for any commercial purpose or for any use other than that granted to the purchaser without the written permission of Canberra Industries Inc Canberra Industries 800 Research Parkway Meriden CT 06450 Tel 203 238 2351 FAX 203 235 1347 http www canberra com The information in this document describes the product as accurately as possible but is subject to change without notice Printed in the United States of America Table of Contents Te INTOQUCION os aia a AA A AA 1 How to Use this Mantal 2 2 Controls and Connectors sosoo 008 ee a 4 Pront Ranol 300 Sw is So G Ae ad a ae ea ee a e es De e 4 Rear Panels panadero a e 5 3 Getting Started Basic Hardware Setup and Configurat
31. Disc 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 Reset Inhibit signal polarity to either Positive or Negative If you are using a TRP preamplifier set the Reset Inhibit polarity of the device to match the po larity of the preamp s Inhibit output Canberra Reset preamps use a positive Inhibit po larity LLD Mode Selects Automatic and Manual LLD modes the digital Lower Level Discriminator se lects minimum input acceptance level With Auto select the LLD cutoff is automati cally optimized just above the spectral noise threshold Manual allows the LLD cutoff to be set manually using the LLD slider bar as a percentage of the full scale spectral size or range The LLD slider bar does not function when Auto is selected LLD Active when the Manual LLD Mode is selected sets the minimum input acceptance level range is 0 to 100 DSP Filter Settings The DSP Filter settings screen Figure 13 for th
32. Function 36 Minimizing or Hiding the Scope From View 00000000 bee eee 37 Digital Oscilloscope Controls and Indicators o o e e o 37 Viewing the Trapezoidally Filtered Detector Pulses o o 40 Using the Digital Oscilloscope to Verify System SetUP o o oo oo 40 Scope Triggering and Pileup Rejector gt o esos oneco o o 41 Basic Spectroscopy Operation 42 Initialization and Self Diagnostics atPowerOn 2 o o 200000000004 42 Spectroscopy System Setup 2 2 e 42 Detector Matching ss s iue au dee a ek ow a ee we ee a i 48 Pole Zero Matching using the Pole Zero Assistant o o e 49 Matching Rise Time and Flat Top Settings to the Detector o 53 Acquiring a SPEC UM s o e sobera e a Ab BA oe a See A a 54 AULOLLD i 5 6 ie Ske as e e as A e e a ade A 54 PUR LTC Operation 55 Pileup Rejection With a Live Source o ee 55 Live Time Correction With a Live SQurCe o ee ee 57 PUR Guatd ec eede se Pee dee BR eh DER OR EEE A ie eS 59 PUR Guard Setup todos ar Gh Gy Seah Soe Oh a ae ee bee Bane ee 61 PUR Guard Adjustment Using a Live Spectrum 2 000 61 Specifications 63 Inputs Outputs gt s e pe ewe rr ED RE EEE Re eR wee REG eS 63 Indicators putos We aves are Gee Goa eee a ee Be ee oe na 64 ConttolS 2 6 bee eee Dee eee Ke Shee RR ORE EE See he EE Dew eS ed 64 Programmable Con
33. HV Polarity Module and remove by lifting up and away from the Main HV board Rotate 180 degrees 91 Configuring the High Voltage Power Supply 92 so that the polarity marking is positioned toward the polarity identifier arrow on the printed circuit board see Figure 43 Carefully reinstall the high voltage Polarity Module into the printed circuit board Make certain the Polarity Module is aligned and fully engaged with the associated connector pin sockets on the high voltage board Figure 43 Changing the High Voltage Polarity Verify the module is installed correctly Check that the polarity identifier arrow on the printed circuit board is pointing to the intended polarity on the HV Polarity Module Changing the High Voltage Range To change the High Voltage Range the following steps are performed Range markings 1 3 KV for 1300 volts and 5 KV for 5000 volts are located on each end of the High Voltage HV Range Module The Polarity identifier arrow is located on the high voltage printed circuit board The identifier arrow pointing to the range marking on the HV Range Module determines the range configuration In Figure 42 the identifier arrow is pointing to the 5 KV marking on the HV Range Module the power supply is configured for the 5 kV full scale range To change the HV Range carefully grasp the HV Polarity Module and remove by lifting up and away from the Main HV board Rotate 180 degrees so that the 1 3 KV polarity m
34. ION 1 part in 4096 all modules RIPPLE 1300 V dc range lt 25 mVpp in 50 MHz bandwidth at maximum voltage and full load 5000 V dc range lt 50 mVpp in 50 MHz bandwidth at maximum volt age and full load TEMP COEFFICIENT lt 50 ppm C after 15 minute warm up 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 15 minute warm up VOLTAGE ACCURACY 5 of setting REGULATION lt 5 variation in output voltage over the load range at constant am bient temperature OVERLOAD PROTECTION The high voltage power supply will withstand any overload including a short circuit for an indefinite period Cables Cables RS 232 provided Used for connecting the instrument to an industry standard com puter 9 pin serial port 3 m 10 ft baud rates supported are 2400 4800 9600 14 4 k 19 2 k 28 8 k 38 4 k 57 6 k and 115 2 k USB provided Used to connect the host industry standard computer USB port to the DSA 1000 rear panel USB port 3 m 10 ft shielded cable Environmental OPERATING TEMPERATURE 0 to 50 C OPERATING HUMIDITY Up to 80 non condensing Physical Metal and Plastic enclosure SIZE 7 1 x 19 1 x 22 6 cm 2 8 x 7 5 x 8 9 in WEIGHT 1 3 kg 2 8 Ib Ordering Information Requires Genie 2000 V2 0A or later 71 Performance Adjustments B Performance Adjustments This appen
35. 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 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 27 aii A PA E vi With PUR ON Figure 27 Comparing Co Spectra w PUR On and Off Live Time Correction With a Live Source 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 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 deploye
36. MCA you want to create a definition for If you are connecting your DSA 1000 to the host computer using the RS 232 interface choose DSA 1000 via D1K 232 If using the USB interface then choose DSA1000 via D1K USB When done making your selection click on the Next button MID Setup Wizard Step 1 Select MCA To start select an MCA device from the list below r Available MCAS H E Network MCAs amp USB MCAS DS4 11000 via D1K USB 12K Simulator InSpector 2000 via I2K USB BY R5232 MCAs JY Desktop inSp Y BSE ector D1K 232 541000 JY Inspector JY InSpector 2000 via 12K 232 Y Nal Inspector E ES Plugin Board MCAs Sf IEEE 488 MCAS Unknown MCAS Figure 3 Selecting the MCA 13 User Interface and Controls Note Figure 3 shows the MID Editor s Add MCA dialog for Genie 2000 V2 1 and later Earlier versions of the MID Editor do not group MCAs by board type Step 2 The step 2 screen will vary depending on your previous selection of the computer in terface type USB Interface For the USB Interface the setup screen will ask you to define the MCA Full Memory the Device Serial Number and Acquisition Mode as shown in Figure 4 The Device Serial Number is the 8 digit serial number located on the bottom of the DSA 1000 in strument MID Setup Wizard Step 2 Enter the serial number of the MCA MCA Full Memory CT 2h Device Serial Number Acq Mode 00000000 PHA C MCS l
37. MCS s Integral mode all valid gamma events processed by the DSP that would otherwise be stored in PHA spectral memory are counted Selecting TTL en ables 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 25 User Interface and Controls 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 15 These commands are not avail able in the Acquisition and Analysis application Define Input Input name DETO m Input Size Channels DetectorT ype Ge y 8192 TF Out of Service K Memory groups 1 256 OK Apply to All Cancel Figure 15 The Define Input 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 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
38. S 232 or USB interface or connecting multiple DSA 1000 s please refer to Appendix E Connecting the Host Computer Serial RS 232 Computer Interface The RS 232 cable is 3 m 10 ft long it allows transfer of computer commands and spectral data between the DSA 1000 and the host computer Getting Started Basic Hardware Setup and Configuration 10 Note The power management on some Lap Top computers may power down the RS 232 port which will disrupt the serial data stream the DSA 1000 If you ex perience random or periodic communication errors this may be due to the Lap Top computer power manager For this case it is recommended to disable the Power Management Features on your Lap Top computer Please consult the User Manual for your Lap Top computer for specific instructions to disable the Power Management Feature Connecting the USB Cable The USB cable is 3 m 10 ft long it allows transfer of computer commands and spec tral data between the DSA 1000 and the host computer Both ends have USB connec tors which are defined by the USB standard one end is rectangular the other end is square Connect the square end to the USB port located on the rear panel of the DSA 1000 connect the rectangular end to the USB port on the host computer Connecting to the Detector Connect the PREAMP power output of the DSA 1000 to the detector using a 9 pin D connector cable assembly Canberra part number C1402 X where x denotes the cable leng
39. Stab C HYPS C Gain Filter Next Gain centroid gt Gain window gt y Gain spacing Gain mode 7680 ch DK 8 chs 64 chs a a VV 9 10 16376 1 128 2 512 Hold Figure 16 Adjust Screen s Stabilizer Settings Acquisition Window Adjust Dialogs Figure 17 shows the relationship between the Stabilizer s Centroid Window and win dow Spacing on a typical peak Centroid Figure 17 Relationship Between Stabilizer Functions 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 adjustment to 0 29 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 stabilizat
40. ables the instrument power is off or the instrument serial number was incorrectly entered when con figuring the MCA Devices dialog box For this case the problem must be cor rected before the data source can be opened If you get a Hardware Verification Error there is a mismatch between the MID Definition setup and the hardware configuration Likely causes are the High Voltage Power Supply configuration or the hardware settings have been changed You can choose to accept or not accept the verification error in the associated dialog box If you select NO a RED error box will appear in the top left corner of the Acqui sition and Analysis window You can determine the source of the verification error by looking at the Status Page which you can access by clicking MCA Status The prob lematic item will be marked with an asterisk The following section describes those parameters for the DSA 1000 that can be ac cessed from the acquisition windows Adjust dialog screen click on MCA Adjust Note that the Adjust screen for a given device may actually be composed of several screens which are accessed by using the Next Prev pushbuttons More detail informa tion about specific function can be found in Chapter 6 Basic Spectroscopy Operation Chapter 7 PUR LTC Operation and Appendix B Performance Adjustments Stabilizer Parameters The Stabilizer settings screen Figure 16 for the DSA 1000 contains the following controls
41. al for its specific high voltage bias requirements The high voltage range and polarity can be verified by physically viewing the high voltage module installation or by viewing the DSA 1000 s front panel HV Status LEDs when the DSA 1000 power is switched ON Again please reference Appendix D Configuring the High Voltage Power Supply for instruction on verifying and chang ing the DSA 1000 s high voltage range and polarity If the DSA 1000 is already oper ational with the computer and Genie 2000 software the high voltage configuration and settings can be verified by reviewing the MCA Front End Hardware Status report in the Gamma Acquisition and Analysis application The Status report can be opened by clicking on MCA and then Status in the drop down menu If the MID definition and the high voltage power supply configuration do not match Genie 2000 will report a hardware verification error when attempting to open the data source For complete in formation on the MID Files and the Gamma Acquisition Analysis application please refer to the Genie 2000 Operations manual It is recommended that the high voltage setting be verified prior to turning the high voltage power supply to ON CAUTION Excessive voltage and or incorrect polarity can permanently damage the detector system Connecting the System Cables Power Connection The AC Power Adapter The DSA 1000 operates by using an ac adapter The AC Power Adapter is connected to the DC PWR
42. an optimize your DSA 1000 s communications by making several trials to look for the best performance Start at a high baud rate and if you don t get performance as good as or better than that shown in Table 2 try a lower baud rate Repeat this until you see an improvement Be sure the tests are made under your standard operating conditions For example if you are going to print while acquiring data you will probably need to lower the baud rate The same is true if you are using the S500 Genie 2000 Basic Spectroscopy software with its copy protection key instead of the S504 InSpector Ba sic Spectroscopy software C Accessory and Cable Part Numbers This section includes part numbers for all accessories cables and HVPS modules in cluded with the DSA 1000 Ttem Canberra Part Number Standard Accessories AC Adapter 95200437 AC Adapter Line Cord 10150007 RS232 Serial Interface cable C1715 10 USB Computer Cable 10302002 HV Power Supply Plug In Modules HV Interlock Board 96_31632 HV Polarity Module 96_31433 HV Range Module 96_31434 Note An underscore _ is included in some part numbers as a place holder for the latest revision letter 87 Configuring the High Voltage Power Supply D Configuring the High Voltage Power Supply 88 gt The high voltage range and polarity should be verified and or setup prior to connecting the DSA 1000 to detector and turning power on Turning the high voltage power supply ON
43. and 1300 V dc Both the positive and negative 5000 volt ranges are adjust able from 1300 volts to 5000 volts and provides up to 20 WA of current suitable for most HPGe detector applications MID Setup Wizard Step 5 13004 1300 0v 0 0v y ok Km gt 1300 0 1300 Voltage limit Voltage il Cancel Help Figure 7 Defining the High Voltage Parameters Both the 1300 volt ranges are adjustable from 10 volts to 1300 volts and provides up to 300 uA of current for detectors requiring lower voltages and or higher current such as Nal or Cd Zn Te 16 The MID Wizard The voltage range and polarity should be set to match the configuration of the high voltage power supply If there is a mismatch the Genie 2000 environment will report a hardware verification error when attempting to open the Data Source in the Gamma Acquisition and Analysis Application To configure the high voltage power supply please refer to Appendix D Configuring the High Voltage Power Supply MID Setup Wizard Step 6 Input Name r Number of Channels l P8192 Detector Type E M El Cancel Help Figure 8 Assigning the Detector Type 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 Ending the Definition To complete your Input Definition select Finish The input that you just defined will be stored as an MID file na
44. approximately 30 adjustment steps at a time The value arrived at by the Pole Zero Assistant may vary slightly when successive adjustments are made this is normal and results from statistical variation associated with the algorithm and system baseline noise Verifying Pole Zero Accuracy The precision of the Pole Zero Assistant operation can be verified by observing the Trapezoid waveform using the digital oscilloscope see Viewing the Trapezoidally Filtered Detector Pulses on page 40 Observe the trailing edge of the Trapezoid waveform as it returns to the baseline It should return with no over or undershoot Set the digital oscilloscope vertical range to an appropriate sensitivity For additional discussion on pole zero verification and manual adjustment refer to Pole Zero Matching Using the Digital Oscilloscope on page 75 Matching Rise Time and Flat Top Settings to the Detector The DSA 1000 allows optimization of the trapezoid filter shape for a variety of detec tors and applications Proper matching will depend on detector characteristics energy range and count rate The digital filter in the DSA 1000 features independent adjust ment of the rise time setting and flat top Therefore the rise time setting which deter mines the noise filtering properties of the digital filter can be optimized independently of the flat top which is set to allow for full collection of detector charge and to reduce the effects of ballistic def
45. arking is positioned toward the polarity HVPS Polarity and Range Configuration identifier arrow on the printed circuit board see Figure 44 Carefully reinstall the high voltage Range Module into the printed circuit board Make certain the Range Module is aligned and fully engaged with the associated connector pin sockets on the high voltage board Figure 44 Changing the High Voltage Range Verify the module is installed correctly Check that the range identifier arrow on the printed circuit board is pointing to the intended range on the HV Range Module Reinstalling the High Voltage Interlock Board To reinstall the High Voltage Interlock board the following steps are performed 1 The High Voltage Interlock Board has four connector pins which must be aligned and engaged with the associated receptacle on the High Voltage Board Orient the Interlock Board so that the caution arrows point toward the rear panel see Figure 45 93 Configuring the High Voltage Power Supply Figure 45 Reinstalling the High Voltage Interlock Board 2 Grasp the HV Interlock board with two hands align the connector pins with the associated connector sockets on the HV board Gently begin engaging the connector pins into the associated connector sockets While monitoring the alignment of the connector pins continue with the installation of the Interlock Board until the connector pins are fully engaged Check to make certain the four pins are aligned and
46. ave the zoom mode clear the Zoom On box Grid Lines Adds a reference grid to aid in waveform measurement The default setting is ON To remove the grid lines clear the Grid Lines box Digital Oscilloscope Controls and Indicators Trigger Select Sets the oscilloscope s trigger source When set to Fast Discriminator the digital os cilloscope will display trapezoid pulses that are detected by the fast discriminator When set to Inhibit the digital oscilloscope will display the trapezoid filter signal during and immediately after the filter overload caused by a preamplifier reset This allows you to view the filter baseline during the reset recovery period The Inhibit setting is used with reset preamplifiers only Notes The Inhibit Trigger select button is active only if TRP is selected as the Preamp Type in the Setting DSP Filter Device of the MID definition If RC Preamp Type is selected the Inhibit button will be grayed out Scope does not trigger With the Trigger Select set to Inhibit the Digital oscil loscope will not get triggered and the wrong error message may be displayed unless the Reset Preamplifier s Inhibit Signal is connected to the Reset input on the DSA 1000 and the Inhibit Polarity is set correctly For additional in formation on connecting and using the Reset Inhibit function please reference Using the Reset Inhibit Function on page 82 Digital Oscilloscope Error messages If for some rea
47. cilloscope Smoothing Factor can be increased if necessary to remove noise which may obscure the shape of the undershoot or overshoot Notes If the Pole Zero was previously set using the Pole Zero Assistant this setting can be modified or optimized further using the Pole Zero slider bar and the Digital Oscilloscope function If this result differs from that obtained using the Pole Zero Assistant the LED adjustment indicators should be ignored Some systems may exhibit undershoots or other secondary time constant anomalies as the trapezoid signal returns to the baseline Short fast secondary time constants sometimes result from parasitic effects stray inductance capac itance associated with the feedback resistor The waveforms shown in Figures 31 through 33 exhibit a short time constant which is typical of this effect If the fast decay time constant is less than 20 mV refer to the digital scope vertical scale its impact on performance is insignificant Pole Zero Matching Using the Digital Oscilloscope Undershoots with longer time constants may also occur due to excessive di electric absorption associated with the preamp feedback capacitor or preamp differentiator circuit Nal detectors also produce short secondary time con stants due to the scintillation material and light decay time constant These short time constants are not associated with the preamp decay time and cannot be corrected using the pole zero compensation However 1f p
48. cilloscope open competes for computer resources which may slow down the PZA Quality Indicator update rate For optimal PZA performance temporarily set the MCA Acquire to OFF and minimize or close the scope window Pole Zero Assistant Error Messages If the Pole Zero Assistant PZA is unable to accurately measure the pole zero value one of the messages below will appear below the Quality Indicator display The error message will extinguish when the error condition is corrected Count Rate Too Low If this message appears the Input Count Rate ICR is too low or the DSA 1000 is not connected to the detector or test pulser The PZA requires a minimum ICR of 40 cps to operate correctly The corrective action would be to verify the detector is properly connected and or adjust the source count rate Count Rate Too High This message appears for the following conditions e The ICR is above 20 kcps e The Fast Discriminator Mode is set to Manual and the Fast Discriminator Threshold is set too low into the noise For this condition the fast discriminator function is responding to noise producing an ICR rate above 20 kcps The corrective action is to lower the count rate and or set the FDisc Mode to Auto or raise the FDisc Setting if the FDisc Mode must remain set to Manual For information on setting up the Fast Discriminator please refer to the DSP Gain Parameters on page 31 Invalid Data This message may appear if the Digital oscilloscope
49. copy Workstation Host Computer COMMUNICATION INTERFACE DETECTOR and PREAMP 2101 TRP USB 10302002 Cable RS232 C1715 10 Cable Figure 25 Typical Gamma Spectroscopy Connect the intended Preamp to the DSA 1000 Preamp power is provided by means of a 9 pin female D connector Connect the DSA 1000 s AMP IN connector to the Preamp s Output signal connector If the detector preamp is a reset type connect the RESET connector to the preamp s Inhibit connector 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 resolution 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 3 Connect one end of high voltage cable to the SHV connector on the DSA 1000 and the other end to the HV In connector on the preamp If using the High Voltage Inhibit Function connect the cable from the DSA 1000 HV INH connector to the preamp s HV INHIBIT connector This signal shuts down the high voltage power supply if the detector warms up The High Voltage Inhibit input can be programmed for Positive or Negative polarity Please refer to Inh signal on page 22
50. criminated Gamma events counted if they occur within the programmed ROI win dow Programmable Settings 68 Dwell Time Settings 5 00 ms to 10 0 s in 14 steps 5 00 ms 10 0 ms 20 0 ms 40 0 ms 80 0 ms 100 0 ms 200 0 ms 400 0 ms 800 ms 1 0 s 2 0 s 4 0 s 8 0 s and 10 0 s Dwell Time Resolution Less than 10 us Sweep Counter 65 535 sweeps ROI Disc Window 1 to 8192 channels Sweep Mode Sweep Counter or Sweep Forever MCS Channel Range 256 to 8192 START STOP CONTROL Software Performance Performance 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 8 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 NON LINEARITY lt 0 025 of full scale over the top 99 of se lected range DIFFERENTIAL NON LINEARITY lt 1 over the top 99 of the range includ ing the effects from integral non linearity GAIN DRIFT lt 33 ppm C after 15 minutes of operation ZERO DRIFT lt 3 ppm C after 15 minutes of operation Typically less than 1 channel over full temperature range 8K Spectrum OVERLOAD RECOVERY Recovers to within 1 of full scale output from x1000 overload in 2 5 non overlapped pulse widths at full gain at an
51. d Filter Reset Period Selecting and Optimizing the Genie 2000 Display Preferences The DSA 1000 s performance is most affected by the communications burden being placed on the system The more communications you demand of your system the slower the response will be For instance the software is at its busiest when the DSA 1000 is acquiring data and scaling it for display To get the best absolute best performance set your system up as follows e Under Display Preferences set the plot mode to Normal Plot which is meant to be used during data acquisition Using the Full Plot mode which is meant for close interaction with an acquired spectrum may reduce the spectral update rate performance e You should normally turn off the Marker Info status page during acquisition When this page is displayed the system has to calculate centroids area integral etc at each update This adds a processing burden that slows the update rate If you do not need the Marker Info page to monitor an ROI for instance make sure the markers are set around the ROI If you leave the markers set to full spectrum there is more data to analyze which will make your screen update noticeably slower 85 Performance Adjustments 86 e The spectral update rate depends on the selection of RS 232 or USB computer interface spectral size and incoming count rate ICR Table 2 below illustrates typical spectral transfer rates for the RS 232 and USB
52. d by computer control range 45 us to infinity a digital oscilloscope and Pole Zero Assistant is provided as a user aid when optimizing the pole zero setting The Pole Zero Assistant measures and analyzes the tail of the trapezoid signal and pro vides visual feedback showing the quality of the pole zero adjustment via a simulated null meter or Pole Zero Quality Indicator PREAMP TYPE RC RESET selects the pole zero mode RC pole zero can be ad justed manually by computer command range 45 us to infinity RESET Sets pole zero at infinity for use with pulsed charged restoration RESET preamplifiers Digital Oscilloscope Allows examination of the digital trapezoid signal reconstructed in time to assist and verify instrument setup pole zero optimization and manual Reset Preamp INHIBIT adjustments HVPS VOLTAGE RANGE Programmable Modules Output voltage range and polarity selected by plug in programming modules 10 to 1300 V dc 1300 to 5000 V dc 10 to 1300 V de and 1300 to 5000 V dc module configuration is read by firm ware and displayed on the front panel and through the host application Low end of the 5000 V range is limited to 1300 V VOLTAGE LIMIT Sets maximum voltage limit of voltage range selected 10 to 1300 V dc 1300 to 5000 V dc 10 to 1300 V de or 1300 to 5000 V dc Volt age range and polarity selected by plug in programming modules STATUS ON OFF sets the HVPS ON or OFF VOLTAGE Allo
53. d off or set to zero On the DSA 1000 this is accomplished by setting the preamp type to RESET The preamp type is selected in the Settings DSP Filter device of the MID Definition 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 required If the RC Preamp Type is se lected the pole zero value on the second page of the MCA Adjust Filter dialog must be manually set to zero Using the Reset Input and Inhibit Function During the preamp reset interval the preamp reset event produces a large signal driv ing the DSA 1000 into severe overload The DSA 1000 automatically senses 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 that the preamplifier s Inhibit signal be connected to the Reset Inhibit input on the DSA 1000 and the Inhibit Polarity be set appropriately Figure 37 shows a representa tion of the Trapezoid signal at the output of the digital filter as well as the Preamp Output and Inhibit signals Amp Out o ee Output Reset inhibit Figure 37 Monitor Output TRP Output TRP Inhibit Operation with Reset Preamps The DSA 1000 system inhibit is initiated or derived from the Inhibit signal generated by the Reset Preamp The optimum system inhibit time can be set automatically by the DS
54. d on both traditional analog electronic and the DSA 1000 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 of the DSA 1000 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 tim ing resolution the fast channel employs little or no noise filtering As a result the sig nal 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 1000 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 The LT Trim has an adjustment value of 0 to 1000 and the default value is 500 which gives good Live Time correction performance for most applications In the steps that follow Live T
55. d time and counts in the reference peak area 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 count 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 ballis tic 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 Tp T pjat Top Where GT PUR Guard Time selection 8 selections ranging from 1 1 to 2 5 are provided Tp Filter Rise Time selection Triat 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 28 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 expec
56. dix describes how to make several performance adjustments adjusting the rise time and the flat top optimizing the pole zero manually setting the baseline re storer setting the fast discriminator threshold operating the DSA 1000 with reset preamps and selecting and optimizing the Genie 2000 Display Preferences Rise Time and Flat Top Adjustments 72 The digital filter employed in the DSA 1000 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 Digital Filter while the Flat Top allows for the charge collection time of the particular detector Independent adjustment of the flat top allows the shaping function to be opti mized for detectors with long charge collection time without a large increase in the overall processing time For small detectors with minimal charge collection time varia tion 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
57. djustments be sure to save the MID File 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 8a Gain Device Adjust Screen Coarse Gain Fine Gain S Fine Gain FDisc Mode LT TRIM LTC Mode PUR Guard Inp Polarity LLD Mode x10 x1 0001 x1 000002 Auto 500 On 1 1x Set Positive or Negative to match the signal polarity from the detector preamp Auto 8b 8c 8d Spectroscopy System Setup Filter Device Adjust Screen Rise Time 5 6 us Flat Top 0 8 Us BLR Mode Auto Pole Zero 3200 Note Please see Rise Time and Flat Top Adjustments on page 72 for additional information on setting the Rise Time and Flat Top settings and their relationship to traditional Gaussian shap ing times High Voltage Device Adjust Screen Set the Voltage setting to the operating bias voltage required for the intended detector The Voltage scroll bar sets the output voltage of the HVPS between the voltage limit s minimum and maximum setting The voltage can also be typed in from the keyboard then accepted with the OK button within the control Note The voltage range polarity and maximum setting are selected in the MID Definition For additional information please refer ence High Voltage Settings on page 20 for configuring the MID Definition
58. e DSA 1000 contains the following controls 23 User Interface and Controls 24 DSP Filter for input USB_RC RC 0 8 C TRP X 5 6 Rise Time BLR mode Auto Fi type a Top FDisc shaping C Low energy Apply to All Figure 13 The DSP Filter Settings 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 40 rise fall times ranging from 0 4 to 38 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 72 BLR Mode Sets the baseline restorer mode When set to AUTO the baseline restorer is automati cally optimized as a function of trapezoid shaping time and count rate With settings of SOFT MEDIUM and HARD the baseline restorer is set to fixed rates as selected Preamp Type Selects the Preamplifier type as either TRP Transistor Reset Preamp type or RC resistor capacitor feedback type RC enables the Pole Zero Assistant function and Pole Zero setting slider bar in the MCA Adjust Filter Device screen Selecting TRP disables the Pole Zero Assistant function the Adjust Screen becomes hidden and enables the TRP Inhibit settings in the MCA Adjust Filter Device screen This control can only be set via the MID Editor
59. e Quality Indicator pointer variation and history bar are approximately centered around the target vertical centerline When this is attained the Pole Zero is properly adjusted and further adjustment is not necessary Adjustment Tips 1 Start the adjustment by grabbing the pole zero slider bar tab button with the mouse pointer Without releasing slide the tab in the direction that moves the Quality Indicator pointer in the desired direction Do not release the slider bar tab yet move the slider bar tab until the Quality Indicator pointer moves back and forth around the target null point or centerline When this is accomplished release the pole zero setting slider bar tab Finish the adjustment by clicking in the adjustment area of the slider bar 30 adjustment steps or the left right arrows for fine adjustments In general the adjustment is complete if the pointer remains near the centerline null point The pointer on the PZA Quality Indicator will vary slightly as a function of time This is normal and results due to the influence of noise as described above 51 Basic Spectroscopy Operation 2 The PZA Quality Indicator incorporates averaging it may respond slower and lag behind quick changes made to Pole Zero Setting Don t make changes to the pole zero setting too quickly allow sufficient time for the Quality Indicator to catch up for an accurate pole zero measurement and indication 3 Having the MCA in Acquire or the Digital Os
60. e greater of the external Reset signal OR the Internal Inhibit Time MANUAL functionality same as Auto mode except the signal processor is inhibited for the greater of the user se lected Inhibit Setting OR the external Reset signal OR the Internal Inhibit Time INHIBIT SETTING Active when the MANUAL Reset Preamp Inhibit Mode is se lected sets the Inhibit Time range 0 to 160 us in increments of 1 us LTC MODE ON OFF ON Enables pileup rejector and live time corrector LTC LTC generates dead time to extend the acquisition time to compensate for events that are piled up and rejected OFF pileup rejector and LTC disabled LT TRIM Allows adjustment of the trapezoidal pulse evolution time or dead time to optimize Live Time Correction LTC performance The adjustment range is 0 to 1000 the default value of 500 provides good LTC performance for a wide range of ap plications Filter 66 Note Filter output Trapezoid Signal may be displayed on the Host computer using the digital oscilloscope feature RISE TIME 40 rise and fall times ranging from 0 4 to 38 us FLAT TOP 21 flat top time selections ranging from 0 to 3 us BLR MODE AUTO HARD MEDIUM SOFT AUTO The baseline restorer is au tomatically optimized as a function of trapezoid shaping time and count rate HARD MEDIUM or SOFT Sets the baseline restorer to fixed rates as selected Programmable Controls POLE ZERO Pole zero is adjuste
61. e refer to the specific USB hub user manual As with connecting a single DSA 1000 using the USB port a hardware configuration must be created in the MID Definition The DSA 1000 devices are uniquely identified using the hardware serial numbers The serial number is an 8 digit number that is af fixed to the bottom of each DSA 1000 Please refer The MID Wizard on page 13 for instruction on configuring the hardware for USB operation USB Standard Class and Cable Information USB standard Class and Cable Information The DSA 1000 is compatible with the Universal Serial Bus Specification Rev 1 1 The USB specifications are available from the USB Web Site at USB ORG e All Canberra USB devices are configured as a Vendor Specific Interface Class the DSA 1000 belongs to the MCA subclass e The DSA 1000 conforms to the Low Power Function defined by the USB spec e The DSA 1000 is a high speed USB function which operates at 12 MB s rate in accordance with the USB standard e The maximum cable length supported by USB is 5 meters 99 Installation Considerations F Installation Considerations This unit complies with all applicable European Union requirements Preventive Maintenance Preventive maintenance is not required for this unit When needed the front panel of the unit may be cleaned Remove power from the unit before cleaning Use only a soft cloth dampened with warm water and make sure unit is fully dry
62. ecovery time beyond the norm The effect often becomes more noticeable at high gains To use the DSA 1000 manual inhibit adjustment set the Inhibit Mode to Manual This setting can be changed on the third page of the MCA Adjust Gain screen Before adjusting the Inhibit Setting the Preamp Type must have been previously set to TRP using the Settings DSP Filter device in the MID Definition If this is not first done the inhibit controls are not available in the MCA Adjust Filter dialog The Inhibit Setting slider bar can adjust the inhibit duration between 0 and 160 us and becomes active in the Manual Inhibit Mode The optimum Inhibit time is determined using the DSA 1000 Digital Oscilloscope first launch the oscilloscope application See Chapter 5 Using the Oscilloscope Func tion for further information on the Digital Oscilloscope With the MID Definition configured for Reset type preamps the Digital Oscilloscope is launched by pressing the Digital Oscilloscope icon button on the toolbar If the Digital Oscilloscope icon is not already available on the main toolbar it can be added by following these steps 83 Performance Adjustments 84 1 Choose the Commands tab on the Gamma Acquisition and Analysis window s Display Preferences Toolbar Setup screen 2 Choose the MCA Category icon group and drag the oscilloscope icon to the toolbar This pushbutton will now be available for launching the digital oscilloscope 3 T
63. ector Matching on page 48 or Pole Zero Matching Using the Digital Oscilloscope on page 75 Pileup Rejection With a Live Source 7 PUR LTC Operation The Model DSA 1000 Digital Spectrum Analyzer includes a pileup rejector and live time corrector The pile up rejector inspects for pulse pileup and allows only 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 DSA 1000 generates a dead time DT signal which extends the collection 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
64. es in channels provided on each side of the aluminum base Its not necessary to fully remove the cover but if it inadvertently comes off make certain it engages the channels on each side of the base when reinstalling it Figure 41 High Voltage Interlock Board Exposed 90 HVPS Polarity and Range Configuration 3 Carefully grasp the High Voltage HV Interlock Board with both hands lift to disengage from the High Voltage Power Supply area as shown in Figure 42 Figure 42 High Voltage Interlock Board Removed For safety the HV Interlock Board removes power from the high voltage power supply if the DSA 1000 Power is inadvertently left on Set the HV interlock board aside Approximately 20 seconds are required for the high voltage to bleed down to safe value after the high voltage is shut off Changing the High Voltage Polarity To change the High Voltage Polarity the following steps are performed 1 Polarity markings for positive and for negative are located on each corner of the high voltage HV Polarity Module The Polarity identifier arrow is located on the high voltage printed circuit board The identifier arrow pointing to the polarity marking on the HV Polarity Module determines the polarity configuration In Figure 42 the identifier arrow is pointing to the marking on the HV Polarity Module the power supply is configured for negative high voltage 2 To change the HV Polarity carefully grasp the
65. etailed information on using the MID Editor Note MCS will be available only if the MCA Acq Mode under Devices was previ ously configured for MCS otherwise is grayed out See Figure 9 MCA Settings This device has no adjustable controls 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 a refer ence peak in the spectrum and correcting the system gain to keep the peak from drift ing The count rates in the reference peak should be high enough to be significantly more than the background in the chosen stabilizer window The MCA Input Definition Editor Settings Summary Help MCA Sample lLHanger ADE MEE Stabilizer Amplifier High Voltage Power feign ACUUT DSF Gain DSF Filter HES Pulser Input Figure 9 The Settings Menu Selecting the Stabilizer command pops up the Dialog Box shown in Figure 10 Digital Stabilizer for input USB Gain centroid 7680ch Ok q ae 1 8193 Gain window Gain spacing Gain ratio al 1 8 chs 64 chs 1 000 C CE E E gt 128 2 512 0 01 100 00 Gain rate div Correction rng DK soon r Figure 10 Stabilizer Settings Dialog 19 User Interface and Controls Note This window s initial focus is on the Cancel bu
66. from 10 volts 1300 volts and provides up to 300 uA of current for detectors requiring lower voltages and or higher current such as Nal or Cd Zn Te The Range control must be set before the Voltage Limit or Voltage Control is ad justed this automatically changes the upper value for the Voltage Limit and Voltage controls This control can be set only in this Dialog Box it cannot be changed in the Acquisition 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 voltage of the HVPS between 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 con trol The MCA Adjust HVPS dialog in the Acquisition and Analysis application al lows you to adjust the output voltage as well as turn the HVPS on and off and reset it 21 User Interface and Controls Inh Signal Sets the polarity of the HV Inhibit input All Canberra detectors and preamps use the Positive setting For additional information refer to Appendix A Specifications DSP Gain Settings The DSP Gain settings screen Figure 12 for the DSA 1000 contains the fo
67. fy correct operation of the hardware The instrument s internal self di agnostics will activate the following indicators for approximately one second POWER FAULT High Voltage Level bar graph 1 3 kV 1 3kV 5 kV 5 kV HV Status LEDs and the DEAD TIME bar graph During power on diagnostics the FAULT LED is illuminated If the diagnostics were successful the POWER LED and one high voltage polar ity range indicator should remain active The FAULT LED will extinguish If during diagnostics a fault was detected the FAULT LED will remain on In addition the actions of the POWER and ACQ LEDs will aid with identifying the potential prob lem area A FAULT LED and blinking POWER LED indicates a problem with the ac adapter or signal processing logic A FAULT LED and blinking ACQ LED indicates a problem was detected with the microprocessor ram data memory loading the FPGA logic or FPGA communication After the self diagnostics completes or any time thereafter a FAULT LED in conjunc tion with a blinking HV LED indicates a HV Inhibit or high voltage power supply fault If the POWER LED remains on no fault condition was detected and the DSA 1000 instrument is configured in the MID Definition the DSA 1000 is ready for operation Please refer to Chapter 4 User Interface and Controls for configuring the Genie 2000 MID Editor 11 User Interface and Controls 4 User Interface and Controls 12 This chapter provides basic information on
68. g the Preamp Reset Mode o e moa a a a E 81 Pole Zero Setting for Reset Preamps o oo 0000 ee eee ee 82 Using the Reset Input and Inhibit Function 2 2 o e e 82 Automatic Inhibit Modes sa 2 acep m ade a oa a e aa a D e a ae aai a AA 83 Manual Inhibit Mode was ce o o cese serenos 83 Selecting and Optimizing the Genie 2000 Display Preferences o o 85 C Accessory and Cable Part Numbers 87 D Configuring the High Voltage Power Supply 88 HVPS Polarity and Range Configuration e 89 Accessing the High Voltage Programming Modules o o 89 Changing the High Voltage Polarity o o a 91 Changing the High Voltage Range a 92 Reinstalling the High Voltage Interlock Board o o 93 Reinstalling the Top Cover and Front Panel 2 2 o o ee 94 Genie 2000 Software Configuration 2 0 ee 95 High Voltage Plug in Module Part Numbers so cocs apona secante a a 95 E Connecting to the Host Computer 96 Using the RS232 POM co rra is EG Bk Pe oe A oe e wpe a A 97 Connecting to the Host Computer 2 2 ee 97 Connecting Multiple DSA 1000 s 1 2 20 0 0 20 00 02 0000 0000 98 Using the USB Port scs sesia Gh ae oo Bere d Cae ee ode eM AR a a Ghee OE 98 Connecting to the Host Computer 2 2 0 2 2 2000000000000 e a 98 Connecting Multiple DSA 1
69. hat it can be used by the Genie2000 applications Use the Load To command in the Database menu to load the definition Refer to the MCA Input Definition chapter of the Genie 2000 Operations Manual for additional information regarding saving and loading definition files as well as editing existing files More Information on the MID Editor You can find information on Changing the Editor s Summary View Editing an MCA Definition and Using MCA Definition Tables in the MCA Input Definition chapter of the Genie 2000 Operations Manual Acquisition Window Adjust Dialogs The Adjust dialogs are found under the MCA menu in the Acquisition and Analysis application The datasource for the specific instrument must be opened To open a datasource select File Open Datasource then select Detector in the Type box Next select the datasource file and select open In the following Adjust Screen discussion the MCS Adjust Screen and the associated selection button are available only if MCS was selected as the Acquisition Mode when setting up the MCA controls in the Devices MCA screen of the MID Editor If MCS was not selected the selection button and adjust screen are hidden form view 27 User Interface and Controls 28 Notes If you get a Required Hardware Unavailable error likely causes are you may have selected the wrong data source for the instrument there is a problem with the RS 232 or USB communication interface check the c
70. he DSA 1000 executes a set of internal diagnostic analyses checking the status of the microprocessor and its components as well as the signal pro cessing logic A complete set of front panel indicators provides real time information on the DSA 1000 s HV setting system dead time and overall system status How to Use this Manual This manual is a comprehensive reference covering the capabilities and operation of the DSA 1000 2 Controls and Connectors You ll find a brief description of the front and rear panels indicators and connectors here 3 Getting Started and Setup Configuration Read this chapter for instructions on system setup and configuration How to Use this Manual 4 User Interface and Controls This chapter continues with more setup information Most of the controls discussed here are programmable through the host computer s software 5 Using the Digital Oscilloscope This chapter discussed the DSA 1000 s digital scope function 6 Setup and Operation This is the heart of the manual day to day basic spectroscopy operation 7 PUR LTC Operation This chapter details how and why you use the DSA 1000 s Pulse Pileup Rejector and Live Time Corrector PUR LTC feature The Appendices The appendices offer useful information not usually needed in day to day operation Controls and Connectors 2 Controls and Connectors Front Panel This is a brief description of the DSA 1000 s front panel
71. he oscilloscope pile up rejector is turned off when the Trigger select is set to inhibit When viewing and measuring the overload recovery characteristics its best to set the ICR to a low rate between 1 and 5 kcps Otherwise pile up will make it difficult to view the recovery characteristic On some reset preamps the Inhibit signal pulse width is adjustable For preamps with this provision the preamp inhibit time can also be set to inhibit pulse processing during the reset period Consult the Detector Preamp Operator s manual for this adjustment Note that when the DSA 1000 Inhibit Mode is set to Manual the system inhibit dura tion will be the time interval set by the DSA 1000 Inhibit Setting slider bar OR the external preamp inhibit duration whichever lasts longer Selecting and Optimizing the Genie 2000 Display Preferences As shown in Figure 38 the overload recovery time is approximately 70 us with the DSA 1000 Rise Time set to 5 6 us Flat Top set to 0 8 us Coarse Gain of x320 and us ing a Canberra Model 2101 preamp and Co source For this example the Inhibit Time should be set to approximately 70 us Digital Oscilloscope Vertical Scale Display Options T Zoom On 0 050 M Grid Lines Trigger Select Discriminator Inhibit Horizontal Scale Horizontal Delay 20 0 y 5 1 Defaults microseconds div 100 0 microseconds Exit Help te Figure 38 Digital Oscilloscope Waveform Showing Trapezoi
72. her purpose Revised 1 Apr 03
73. hroughput good or equivalent Gaussian shaping resolution Note 2 Optimized for highest resolution equivalent Gaussian shaping processing time throughput Table 1 lists settings for optimizing throughput or resolution Of course a setting in be tween can be chosen to optimize performance for a specific application The Gaussian Equivalent Shaping Times are suggested as starting values You may change these val ues to enhance throughput or resolution as required by your application 73 Performance Adjustments 74 As previously mentioned the shaping times recommended for highest throughput 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 characteri
74. icit in germanium detectors The rise time and flat top set tings are generally a compromise between optimizing for throughput or resolution For a full discussion these settings refer to Pole Zero Matching Using the Digital Oscil loscope on page 75 53 Basic Spectroscopy Operation Acquiring a Spectrum 54 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 1000 setup performed in Spectroscopy System Setup on page 42 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 1000 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 Auto LLD If you have selected the Auto LLD Mode the LLD cutoff is automatically adjusted just above the spectral noise threshold However if the trapezoid signal has excessive undershoot resulting from incorrect Pole Zero adjustment the low end spectral cutoff may be affected when using the Auto LLD Mode If the low end spectral cutoff is higher than expected with Auto LLD selected verify and or adjust the Pole Zero as de scribed in Det
75. if adjustment or repair is required because of damage caused by other than ordinary 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 Service 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 ot
76. ilable only if MCS was selected as the Acquisition Mode when setting up the MCA con trols in the Devices MCA screen of the MID Editor If MCS was not selected the selection button and adjust screen are hidden form view Dwell Time Sets the dwell time value There are 14 selections ranging from 5 ms to 10 seconds Disc Mode The Disc Mode control establishes the MCS mode to be used Selecting Integral en ables the MCS s Integral mode all valid gamma events processed by the DSP that would otherwise be stored in PHA spectral memory are counted Selecting TTL en ables 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 DSP Gain Parameters The DSP Gain settings screen Figure 20 for the DSA 1000 contains the following controls The combination of Coarse Fine Gain and Super Fine Gain SFG sets the overall sys tem gain to match the requirements of the detector and energy application overall gain is continuously variable from x2 24 to x2438 31 User Interface and Controls E Filter Fine gain S fine gain 1 4001 0 999998 m ma eee J 1 900 0 9975 1 0025 Figure 20 Adjust Screen s Gain Settings Coarse Gain Sets the device s coarse gain It s best
77. ile Save command the host computer will down load the last value s saved MID Definition Settings Please verify or set the following setup parameters in your Genie Spectroscopy System s MCA Input Definition MID For complete information on editing MID files refer to the MID Editor chapter in your Genie manual set Ta DSP Filter Gain Settings Preamp Type RC Inp Polarity Set Positive or Negative to match the preamp signal polarity of the intended detector This parameter can be set only in the MID Definition Inh Polarity 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 require a positive Inhibit setting Spectroscopy System Setup This parameter can be set only in the MID Definition 7b HVPS Configuration Please consider and or verify the high voltage range and polarity re quirements for the intended detector application at this time Turning the high voltage power supply ON or OFF and setting the op erating voltage are programmable through the computer and Ge nie 2000 software environment However the polarity and range are manually configured using programming modules the programming modules are conveniently located inside the DSA 1000 The high voltage range and pola
78. ime 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 reference peak area variation using the default LT Trim setting is typically less than 3 for dead times of 50 The dis criminating user can improve performance further for the intended application by cal ibrating the system using the Two Source Method and optimizing performance using the LT Trim 57 PUR LTC Operation 58 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 Co 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 Cs at 2 x 661 6 1323 2 keV would in terfere with the measurement Note 10 Connect and set up the Model DSA 1000 as described in Spectroscopy System Setup on page 42 Verify LTC is set ON Pole Zero Compensation The Pole Zero was previously adjusted and it is not necessary to do it again If for some reason readjustment is necessary refer to Detector Matching on page 48 Set the MCA s preset to 500 Live seconds Position the Co source near the Ge detector and adjust for an incoming count rate of 2
79. in jack located on the rear panel 1t will supply power to the DSA 1000 Use only the DSA 1000 AC Power Adapter Connect the DC jack of the power adapter to the DSA 1000 Connect the power adapter to a suitable AC power source DC power requirements Nominal 7 5 V dc at 0 75 Amps using AC Power Adapter Connecting the System Cables This section provides a step by step instructions for connecting the system cables to the DSA 1000 s rear panel connectors See Figure 2 DSA 1000 Rear Panel on page 5 Connecting to the Host Computer The DSA 1000 supports two serial computer interface systems RS 232 and high speed USB Connect the DSA 1000 to the host computer using the RS 232 or USB in terface as described below If your computer supports USB this would be the better choice since it is a high speed interface which significantly increases the DSA 1000 to host computer response time and data transfer rate The communication interface must be defined and configured in the Genie 2000 MID definition When using RS 232 a baud rate for the COM port must be selected When using USB the DSA 1000 serial number must be entered into the MCA Input Defini tion MID Configuration to allow the Genie 2000 software to identify the specific in strument If this has not already been done please refer to The MID Wizard on page 13 for instruction on defining the DSA 1000 MID input definition for RS 232 or USB operation For more information on using the R
80. in 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 Inputs Outputs A Specifications Inputs Outputs AMP IN Accepts positive or negative signals from an associated detector preamplifier amplitude for full scale conversion 10 V divided by selected gain max imum input signal dc for linear operation is dependent on the Input Attenuator set ting Attenuator OFF x1 4 V Attenuator ON x 0 25 12 V de coupled and protected to 24 V maximum rise time less than the selected Rise Time Flat Top settings acceptable preamplifier decay time constant 45 us to infinity Z is 1 3 KQ rear panel BNC connector RESET Accepts a standard TTL Logic signal functionality is dependent on the Re set Preamp Inhibit mode selected disables pulse processing extends the system dead time resets the pileup rejector and gates off the baseline restorer rear panel BNC con nector Auto System is gated off for the greater of the external Reset signal OR the Internal Inhibit time Manual Functionality same as Auto mode except the signal pro cessor is inhibited for the greater of the user selected Inhibit Setting OR the Internal Inhibit Time OR the external Reset signal Positive true or negative true signal po larities user selectable minimum pulse width is 100 ns logic high 2 2 V logic low lt 0 8 V maximum input voltage
81. ion 7 Unpackinethe DSAS1000 205 ccs we a a a Sa Se ee 7 Initial SUD cercar A Aa AA 8 Power Connection ic ar Qo A cee in oa ee AA ee 9 Connecting the System Cables o eee 9 Connecting to the Host Computer ee 9 Grounding th Systeme sos res ta rd cd oh we a a ee a e 10 Power Ole wid a a ar AO A Gale ao SS ee 11 4 User Interface and Controls 002 0000 0 12 The MUD Wizards ae i ae sire ek BO eo p p a ae en a ea A 13 The MCA Input Definition Editor s ss e s owce sawe ee 18 Editing The MID Settings 2 2 o 18 MCA Settings eo ae A a ee ee et he 18 Stabilizer Settings 2 face Odeo dee eee dee aaa 18 High Voltage Settings e a ee d ee 20 DSP Gain Settings sg sos 3 8 de OS ey a BoE Sw ee doe eS 22 DSP Filter Settings acne waded Renee ARR eee ete eae bea HO 23 MCS Settings uu rc ai he A Pa ee wd a ed ow a A 25 Input SCCM ES e aaee e a oa cael a ent ada 26 Saving and Loading the Input Definition o e e 27 More Information on the MID Editor gt s s s s soemo ee e e 27 Acquisition Window Adjust Dialogs 2 2 ee 27 Stabilizer Parameters o oe errada a a a a Be aoa 28 High Voltages sx a ane ew dk e me ew de ale la ws ge 30 MCS Parametersss x eric Gao oe eo ie ew ote ol te ates Gate Fe Grae or Eat 31 DSP Gain Parameters s o pe eR RO HDR TR HES Oe eS 31 DSP Filter Parameters ocio siuen ake ae A ae ee ee EE ck cas a 33 Using the Digital Oscilloscope
82. ion If TRP Preamp type is selected the Pole Zero setting is set to Infinity and the Pole Zero Assistant Adjust Screen is hidden from view 34 Acquisition Window Adjust Dialogs The Pole Zero is manually adjusted using the P Z slider bar The adjustment range is 45 us to infinity The Pole Zero Assistant and Digital Oscilloscope are provided as user aids when optimizing the pole zero setting The Pole Zero Assistant provides visual feedback of the Pole Zero convergence qual ity via the Quality Indicator The Pole Zero Assistant measures and analyzes the tail of the trapezoid signal and provides visual feedback showing the quality of the pole zero adjustment via a simulated Null Meter or Pole Zero Quality Indicator For additional information on adjusting the pole zero using the Pole Zero Assistant please refer to Detector Matching on page 48 The digital oscilloscope can be opened by clicking on the Oscilloscope icon in the right top corner of the Pole Zero Assistant box When using the Oscilloscope function stop any MCA acquisitions in process to maximize the scope update rate For addi tional information on using the digital Oscilloscope please reference Chapter 5 Using the Digital Oscilloscope Function and Pole Zero Matching Using the Digital Oscil loscope on page 75 35 Using the Digital Oscilloscope Function 5 Using the Digital Oscilloscope 36 Function The digital oscilloscope is provided as a visual aid to a
83. ion 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 High Voltage The High Voltage command shown in Figure 18 adjusts the High Voltage Power Supply HVPS HVPS C Gain Filter Voltage ox gt 1300 1300 Reset HWPS Reset Figure 18 Adjust Screen s HVPS Settings Status This control allows you to turn the HVPS on off Voltage The Voltage scroll bar sets the output voltage of the HVPS between the Voltage Limit s minimum and maximum settings The voltage setting can also be typed in from the keyboard then accepted with the OK button within the control Note The maximum setting may be limited by the Voltage Limit setting in the MID Editor HVPS Reset This control resets any HVPS fault condition for example inhibit or overload 30 Acquisition Window Adjust Dialogs MCS Parameters The MCS settings screen Figure 19 for the DSA 1000 contains the following con trols C Stab C HYPS MCS C Gain Filter Dwell time isc Mode ROI Start ROI End j are 2 ax LE CE a l Help 1 16384 1 16384 Figure 19 Adjust Screen s MCS Setting Note The MCS Adjust Screen and the associated selection button are ava
84. ion rocker switch located on rear panel Programmable Controls Programmable Controls Gain The combination of Coarse Gain Fine Gain and Super Fine Gain SFG set the overall system gain to match the requirements of the detector and energy application overall gain is continuously adjustable from x2 24 to x2438 COARSE GAIN x2 5 x5 x10 x20 x40 x80 x160 x320 x640 x1280 FINE GAIN Range is x0 9 to x1 9 SUPER FINE GAIN Range is x0 9975 to x1 0025 GAIN ATTENUATOR ON OFF When ON selected enables a divide by four in put attenuator to minimize overload due to preamp signals with large dc offsets and Reset Preamps with large output ramp dynamic range Coarse Gain settings displayed include the effects of the attenuator the Coarse Gain selections reduce from 10 to 8 covering a range of x2 5 to x320 When OFF is selected the signal attenuation is re moved MCA INPUT SIZE PHA MODE Selections of 256 512 1024 2048 4096 8192 or 16 384 channels Support for two memory groups of 8192 or less channels MCS MODE Selections of 256 512 1024 2048 4096 or 8192 channels support for two memory groups of 8192 or less channels LLD MODE Selects Automatic or Manual LLD mode AUTOMATIC the LLD cut off is automatically set just above the spectral noise threshold MANUAL allows the LLD cutoff to be set manually as a percentage of the full scale spectral size or range LLD SETTING Active when the Manual LLD mode i
85. ium detector or Nal 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 11 adjusts the High Voltage Power Supply HVPS Note The voltage range and polarity should be set to match the hardware configura tion of the HVPS If there is a mismatch the Genie 2000 environment will re port a hardware verification error when attempting to open the datasource in the Gamma Acquisition and Analysis Application To configure the HVPS please refer to Appendix D Configuring the High Voltage Power Supply 20 The MCA Input Definition Editor High Voltage Supply for input DETO1 00 Ok Positive gt C Negative 0 1300 1 300v 1300 0v 4 gix 0 1300 Range Voltage limit ee OK Apply to Al Figure 11 The High Voltage Settings 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 Range Click on the Range Box to select the desired voltage range The DSA 1000 supports four voltages ranges 5000 V dc 1300 V dc 5000 V dc and 1300 V dc Both the positive and negative 5000 volt ranges are adjustable from 1300 volts to 5000 volts and provides up to 20 uA of current suitable for most HPGe detector applications Both the 1300 volt ranges are adjustable
86. llowing controls DSP Gain for input DETO1 Gain Attenuator _ s Coarse gain Fine gain r S ine gain Off x40 1 4000x 1 000000x on Se a o 0 900 1 900 0 9975 1 0025 FDisc Mode r FDisc Setting Inp Polarity minh polarity Auto 1 0 Positive Positive C Manual Kim C Negative C Negative LLD Mode LLD Auto 0 1 9 mos ms Figure 12 The DSP Gain Settings The combination of Coarse Fine and Super Fine Gain SFG sets the overall system gain to match the requirements of the detector and energy application overall gain is continuously variable from x2 24 to x2438 Gain Attenuator ON enables a divide by four input attenuator to minimize overload due to preamp sig nals with large dc offsets and Reset preamps with large output dynamic range overall gain settings reduce by a factor of four When OFF is selected the signal attenuator is removed 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 The Coarse gain allows selections of x2 5 through x1280 Fine Gain Sets the device s Fine Gain multiplier the adjustment range is x0 900 to x1 900 22 The MCA Input Definition Editor S Fine Gain Sets the device s Super Fine Gain multiplier the adjustment range is x0 9975 to x1 0025 F
87. med inputname MID and automatically loaded into the MCA Runtime Configuration Database When you select Finish 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 17 User Interface and Controls The MCA Input Definition Editor 18 The MCA Input Definition MID Editor allows you to create edit and manage input definitions However for most users the facilities provided in the MID Wizard are sufficient You ll have to use the MID Editor only if you wish to change any of the following parameters from their default values Digital Stabilizer Gain Rate Divider Default 1 Correction Range Default Ge High Voltage Power Supply Inhibit Signal Polarity Default Positive DSP Gain Gain Attenuator Default OFF Reset Preamp Inhibit Polarity Default Positive DSP Filter Preamp Type Default RC FDisc Shaping Default Normal Editing The MID Settings This section discusses the specific settings for the DSA 1000 in the MCA Definition To change any of them refer to the procedures described in Editing an MCA Defini tion in the MCA Input Definition chapter of the Genie 2000 Operations Manual That chapter also has d
88. nd centerline indicates the trapezoid waveform is exhibiting undershoot and the pole zero setting is low Similarly the area to the right of the target null point and centerline indicates the pole zero setting is too high there is too much compensation and the trapezoid wave form is exhibiting overshoot 49 Basic Spectroscopy Operation 50 The pointer presents the current pole zero quality as you would interpret the pole zero setting when viewing the trapezoid signal return to the baseline using the oscilloscope As with all electronic processes noise generally accompanies the signal of interest The noise component causes the instantaneous baseline value and pole zero measurement to statistically vary from the average value Smoothing or averaging is applied to the pole zero measurement algorithm however low frequency noise components statisti cally influences the measurement which cause the Quality Indicator pointer to exhibit a small variation or dither To minimize the effect of the Quality Indicator variation the history of the pointer position is painted behind the pointer The history bar pro vides the effect of additional averaging to assist with making the pole zero adjustment The objective of the pole zero adjustment is to center the Quality Indicator pointer and associated history bar around the null point or center vertical line When accomplished the pole zero adjustment is properly optimized and further adjustment is not requi
89. nts 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 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 61 PUR LTC Operation 62 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 48 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 aga
90. o remove the colored title bar just above the icon click in the colored area with the left mouse button and drag it down 4 The toolbar can now be saved by pressing the Save button on the Display Preferences screen For more information on adding command buttons to the toolbar see Toolbar Setup in the Genie 2000 Spectroscopy System Operations Manual in the Display Preferences section of the Gamma Acquisition and Analysis Once the Digital Oscilloscope is activated set the Trigger Select to Inhibit When using this trigger source make sure that the Inhibit output of the reset preamp has been connected to the DSA 1000 Reset input Otherwise the oscilloscope will not get triggered and the wrong error message may be displayed Note The Inhibit Trigger select button is active only if TRP is selected as the Preamp Type in the Settings DSP Filter device of the Mid Definition If RC is selected as the Preamp Type the Inhibit button will be grayed out The overload recovery time of the trapezoid signal is measured to set the required inhibit time The overload period is marked by the duration of the large negative overload excursion in the oscilloscope waveform Measure the duration of the overload signal in microseconds the overload signal begins with the large negative excursion and ends upon return to the baseline see Figure 38 Set the Inhibit Setting equal to the measured overload time period Adjustment Tips As mentioned in chapter 5 t
91. oached If the ICR exceeds 20 kcps the Count Rate Too High message will be posted The corrective action is to reduce the Horizontal Scale setting and or the ICR The trigger for the rejector is the fast discriminator In order to avoid rejecting reset events accompanied by fast discriminator pulses the rejector is turned off when the In hibit trigger is selected The unit will also reject any pulses which exceed its dynamic range which is somewhat larger than the full scale equivalent of 10 volts Note also that the normal trigger source for the Digital Oscilloscope is the Fast Discriminator If the Fast Discriminator is set in Manual mode then the trigger level can be controlled manually and the digital oscilloscope will display only energy pulses associated with fast discriminator pulses above the manual threshold setting 41 Basic Spectroscopy Operation 6 Basic Spectroscopy Operation This chapter is a quick setup guide and outlines the operation of the DSA 1000 More detailed information about specific functions can be found in Chapters 2 through 5 Chapter 7 and the Appendices Following the procedures below will make you famil iar enough with the instrument to be able to use it effectively Initialization and Self Diagnostics at Power On When the DSA 1000 is first turned ON it will go through an initialization and self test process During the initialization period the DSA 1000 will run internal diagnostics routine
92. od of one 1 year from the date of performance of such services If defects in materials or workmanship are discovered within the applicable warranty period as set forth above we shall at our option and cost A in the case of defective software or equipment either repair or replace the software or equipment or B in the case of defective services reperform such services LIMITATIONS EXCEPT AS SET FORTH HEREIN NO OTHER WARRANTIES OR REMEDIES 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 EXEMPLARY PUNITIVE 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 REPAIR OR REPLACEMENT OF THE SOFTWARE OR EQUIPMENT DURING THE APPLICABLE WARRANTY PERIOD AT CANBERRA S COST OR IN THE CASE OF DEFECTIVE SERVICES REPERFORMANCE AT CANBERRA S COST IS YOUR SOLE AND EXCLUSIVE REMEDY UNDER THIS WARRANTY 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 neglect or unusual physical or electrical stress as determined by our Service Personnel We are under no obligation to provide warranty service
93. onic circuit as opposed to a feedback resistor 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 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 1000 as before or as indicated in Spectroscopy System Setup on page 42 and in Figure 25 For additional information on the Reset Delay feature and jumper plug W1 please re fer to the Model 2101 User s Manual 81 Performance Adjustments 82 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 compensation should be turne
94. onnector The maximum cable length supported by USB is 5 m PREAMP Provides 24 V 5 12 V 5 and ground for standard preamplifiers overload protected 24 V at 40 mA max 24 V at 20 mA max 12 V at 80 mA max 12 V at 30 mA max Rear panel 9 pin female D connector Indicators Controls 64 POWER Green LED indicates that the DSA 1000 is switched on FAULT Yellow LED indicates a diagnostic failure at power up or high voltage fault HV ON Green LED indicates HVPS status or HV fault condition constant on indi cates HVPS is on and high voltage may be present at the rear panel SHV connector Blinks for a fault condition such as a high voltage overload or inhibit due to a detector warm up if connected HV Level Green LED bar graph indicating the high voltage present at the rear panel HV connector The bar graph full scale FS depends on the selected HV range 1 3 kV or 5 kV HIGH VOLTAGE Range and Polarity Four green LEDs indicating the selected HV range and polarity ACQ Green LED indicates MCA is acquiring COMM Green LED indicates USB or RS 232 activity ICR Green LED indicates incoming count rate blink rate proportional to count rate DEAD TIME Green LED bar graph providing a real time display of the system s dead time in percent range 0 100 linear POWER Power to the DSA 1000 is enabled when the switch is set ON T posi tion OFF for the O posit
95. or OFF and setting the output voltage set ting are programmable through the computer and Genie 2000 software environment However the polarity and range are manually configured using programming mod ules the programming modules are conveniently located inside the DSA 1000 The high voltage range and polarity are preset at the factory for the positive 5000 volt range which is compatible with many Ge detector applications If your detector re quires negative polarity or the higher current 1300 volt range please reference HVPS Polarity and Range Configuration on page 89 for instructions on changing the DSA 1000 s high voltage range and polarity Please consult your detector s manual for its specific high voltage bias requirements The high voltage range and polarity can be verified by physically viewing the high voltage module installation or by viewing the DSA 1000 s front panel HV Status LEDs when the DSA 1000 power is switched ON If the DSA 1000 is already opera tional with the computer and Genie 2000 software the high voltage configuration and settings can be verified using the Status Page associated with the Gamma Acquisition and Analysis GAA application The Status Page can be opened by clicking on MCA then Status in the drop down menu If the MID Definition and high voltage power sup ply configuration do not match Genie 2000 will report a hardware verification error when attempting to open the data source in the GAA window For
96. ption of the DSA 1000 s rear panel connectors and power switch For more detailed information refer to Appendix A Specifications O O IN INH POWER PREAMP DC PWR o de M m 5V 0 75A Figure 2 DSA 1000 Rear Panel Power Switch The DSA 1000 s power switch 1 0 located on the rear of the unit controls power to the instrument Power is enabled when the switch is in the 1 position and disabled when the switch is in the 0 position The POWER LED continuously illuminates green when the power switch is ON and the instrument is powered from the power adapter Controls and Connectors Connectors RESET MCS AMP IN HV INH HV USB RS232 DC PWR PREAMP CAUTION Reset inhibit input signal connection when using reset type preamp rear panel BNC MCS count input connector for receiving external TTL signal rear panel BNC connector Input coax connection for receiving detector preamplifier signal rear panel BNC Preamp high voltage inhibit input connection rear panel BNC High Voltage output connector rear panel SHV USB computer port for connecting to host personal computer rear panel Series B connector RS 232 computer interface for connecting to host personal com puter 9 pin male D connector rear panel auto sense selection of data rates 2 4 4 8 9 6 14 4 19 2 28 8 38 4 57 6 and 115 2 kbaud DC power input 2 5 5 5 mm rear panel connector Nominal 7 5 V dc
97. r NIM bins The heart of the DSA 1000 is the Digital Signal Processor subsystem Unlike conven tional systems which digitize the signals at the end of the signal processing chain the DSA 1000 digitizes the preamplifier signals at the front of the signal processing chain This approach minimizes the amount of analog circuitry resulting in increased stabil ity accuracy and reproducibility The use of DSP technology also improves the overall signal acquisition performance Signal filtering functions previously implemented in traditional analog electronics are limited DSP allows filtering functions and pulse shapes that are not realizable using conventional analog processing techniques The result is a more efficient trapezoidal filter function which exhibits less processing time less sensitivity to ballistic deficit and superior resolution With trapezoidal filtering the pulses can be processed more rapidly and accurately so the spectrum resolution is enhanced while throughput is in creased The DSA 1000 offers peak gain stability in some cases a factor of two to three times better than past generation analog products while Zero drift is barely measurable over the full operating temperature range of the instrument The DSA 1000 supports both the traditional Pulse Height Analysis PHA mode as well as a multichannel scaling MCS mode for time varying applications The MCS mode can display data from either an external TTL input a full spect
98. red The Pole Zero Assistant will give good results for most detector applications and count rates However there may be some applications or circumstances where it may be necessary to use the Digital Oscilloscope when optimizing the pole zero compensa tion Examples include detector applications which produce excessive baseline noise high count rate operation or 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 characteristics which produce multiple time con stants making the tail pulse fall time non monotonic This behavior may become problematic at high count rates causing significant baseline perturbations and resolu tion degradation Nal detectors may have multiple time constants due to AC coupled preamps and scintillator interactions In these situations it may also be possible to opti mize performance further by fine tuning the pole zero using the Digital Oscilloscope Refer to Pole Zero Matching Using the Digital Oscilloscope on page 75 The Pole Zero Assistant automatically operates and shows the Pole Zero adjustment quality whenever RC is selected for the preamp type and the Pole Zero Assistant screen is open The Pole Zero Assistant Screen is accessed by first selecting the Ad just MCA Filter screen and then pressing the Next button The screen consists of a simulated Null Meter or Quality Indica
99. resent they should not be confused with undershoots caused by the preamp decay time which can be compensated using the Pole Zero adjustment Figure 31 below shows the correct setting of the P Z adjustment while Figures 32 and 33 show under and over compensation of the preamplifier decay time constant As illustrated for correct P Z compensation the digital oscilloscope waveform should have a clean return to the baseline with no overshoots or undershoots PA Vertical Scale Display Options T Zoom On 0 025 al oa Grid Lines iv 0 005 Vertical Offset i i i i Trigger Select e Fast Discriminator C Inhibit Smoothing Factor Horizontal Scale Horizontal Delay 8 20 0 dia Ho Defaults 05 microseconds div 100 0 microseconds Figure 31 Correct Pole Zero Compensation Digital Oscilloscope Vertical Scale Display Options T Zoom On 0 025 a F Grid Lines div H i i i 0 005 Vertical Offset Trigger Select i y e Fast A Discriminator C Inhibit Smoothing Factor Horizontal Scale Horizontal Delay 8 20 0 32 amn n Defaults 32 0 5 microseconds div 100 0 microseconds Figure 32 Undercompensation Pole Zero 77 Performance Adjustments 78 M Digital Oscilloscope Display Options T Zoom On M Grid Lines Trigger Select e Fast Discriminator Inhibit Horizontal Scale Horizontal Delay 20 0 3 2 AqA AIMM Defaults 05 microseconds div 100 0 microseconds 3
100. rial Bus communication inter face The following discussion will guide you in connecting the DSA 1000 to your host computer Information is provided below to e Help you select which communication interface to use e Connect the appropriate cable e Identify and select the appropriate communication port and baud rate when using the RS232 Port e Identify the DSA 1000 serial number which serves as the unique device number when using the USB Port On IBM compatible computers the RS232 interface is also known as a COM Port It is a bi directional serial interface for low to medium speed data transfer with peripheral devices The maximum transfer rate is depended on the capabilities of the specific computer and cable length being used but is limited to less than 115 200 bits per second Also most computers have only two COM ports which limits the number of devices that can be attached at any given time The USB Universal Serial Interface is a high performance high speed serial inter face that is available on most new computers It can accommodate a data transfer rate up to 12 megabits per second as opposed to 100 Kbits per second of the RS232 serial interface Most computers provide a minimum of two USB ports Each USB port can accommo date up to seven devices with the addition of a USB Hub The number of total USB devices can be expanded up to 127 with additional USB hub devices However in practice the actual number of DSA 1000 inst
101. rity are preset at the factory for the positive 5000 volt range which is compatible with many Ge detector applica tions If your detector requires negative polarity or the higher current 1300 volt range please reference Appendix D Configuring the High Voltage Power Supply for instructions on changing the DSA 1000 s high voltage range and polarity Please consult your detector s manual for its specific high voltage bias requirements The high voltage range and polarity can be verified by physically viewing the high voltage module installation or by viewing the DSA 1000 s front panel HV Status LEDs when the DSA 1000 power is switched ON Again please reference Appendix D Configuring the High Voltage Power Supply for instruction on verifying and changing the DSA 1000 s high voltage range and polarity If the DSA 1000 is already operational with the computer and Genie 2000 software the high voltage configuration and settings can be verified using the Sta tus Page associated with the Gamma Acquisition and Analysis GAA window The Status Page can be opened by clicking on MCA and then Status in the drop down menu If the MID Definition for the high voltage power supply configuration do not match Genie 2000 will re port a hardware verification error when attempting to open the data source in the GAA window For complete information on the MID Files and the Gamma Acquisition and Analysis window please refer ence the Genie 2000 Operations man
102. rol is required to maintain the baseline such as with some Nal TI scintillation de tector systems or detectors which exhibit excessive microphonics Manual Fast Discriminator Threshold 80 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 detector 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 3 Operation with Reset Preamps 5 The following steps optimize the discriminator sensitivity to insure the threshold is at its lowest setting just above the noise level 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 1000 s GAIN is changed Operation with Reset Preamps The DSA 1000 is fully compatible with most pulsed reset preamplifiers Reset preamps use an electr
103. rovides good LTC performance for a wide range of applications For additional information on using the LT Trim function please refer to Live Time Correction with a Live Source on page 57 LLD Mode Selects Automatic or Manual LLD modes With Automatic selected the LLD cutoff is automatically set just above the spectral noise threshold Manual allows the LLD cut off to be set manually as a percentage of the full scale spectral size LLD Sets the minimum input acceptance level active only when Manual LLD mode is se lected adjustment range is 0 0 to 100 of the spectrum full scale range Note The Inhibit Adjust Screen and Inhibit controls described below are available only if TRP preamp type is selected in the Settings DSP Filter Devices in the MID Editor If RC Preamp type is selected the Inhibit Adjust Screen and con trols are hidden from view Inhibit Mode Selects the Auto or Manual Inhibit Mode AUTO gates the system off for the greater of the Reset Preamp Inhibit Time OR the internal inhibit time MANUAL gates the system off for the greater of the adjustable Inhibit Setting OR the Reset Preamp In hibit time OR the internal inhibit time Inh Setting Active when the Manual Reset Preamp Inhibit Mode is selected sets the Inhibit Time range 0 to 160 us DSP Filter Parameters The DSP Filter settings screen Figure 21 for the DSA 1000 contains the following controls Rise Time Symmetrically sets
104. rum integral or a Region of Interest ROI Introduction Two methods of host communications are supported The preferred method is the Uni versal Serial Bus USB interface which provides fast host communications at 12 Mbits second USB provides the additional capability of having multiple units at tached to a single host port via a USB hub USB requires the use of either Windows 98 Windows Me or Windows 2000 operating environments The second method of host interface is a standard RS 232 serial connection Due to the communications rate constraints of serial ports the DSA 1000 has been designed for highly compressed optimized communications To facilitate optimal pole zero adjustment the DSA 1000 is equipped with a Pole Zero Assistant PZA feature The PZA allows the user to adjust the pole zero cancellation circuit while the DSA 1000 analyzes and displays the degree of overshoot and under shoot exhibited by the filtered signal The user simply moves the P Z control until the PZA indicator is centered indicating optimal adjustment Purists who wish to view the actual signal while adjusting pole zero or other parame ters will use the digital oscilloscope function implemented with the DSA 1000 and host computer software With the digital oscilloscope the user views a graphical reconstruction of the digi tized filtered signal Scaling and trigger functions are similar to those of an actual os cilloscope Upon initial power up t
105. ruments will be limited by host computer performance and available USB bandwidth The USB port is plug and play which makes adding peripheral devices easy there is no need to set DIP switches or IRQ s The only requirement is that Genie 2000 soft ware be configured with the unique DSA 1000 device serial number Using the RS232 Port Hot swapping is another advantage of USB you can plug and unplug USB periph eral devices while the computer is on The USB also distributes and powers USB com patible peripheral devices The computer automatically senses the device power requirement and delivers it to the device The DSA 1000 uses only a small amount of power from the USB buss total power consumption from the USB buss is less than 1 USB unit load which is less than 100 WA Note Canberra s USB driver is a Microsoft Win32 Driver Model WDM compati ble with Windows 98 and future versions of Windows i e Windows 2000 However Windows 95 is not supported since not all the driver functions are supported under WDM for Windows 95 Using the RS232 Port Connecting to the Host Computer The RS232 cable is 3 m 10 ft long it allows transfer of computer commands and spectral data between the DSA 1000 and the host computer The communication interface must be defined and configured in the Genie 2000 MID Definition Please refer to The MID Wizard on page 13 for instruction on assigning COM ports and baud rates Baud rates of
106. s which dis play many traces at once typically grouped around the energy peaks Note If your detector is neutron damaged or exhibits excessively long charge collec tion time it is recommended the scope averaging be set off Otherwise the long tails associated with the long collection times will be averaged into the smoothed trapezoid signal and give the wrong impression regarding the pole zero setting Scope Triggering and Pileup Rejector Scope Triggering and Pileup Rejector In order to prevent piled up pulses from distorting the waveform viewed on the digital oscilloscope and to prevent extraneous pulses from disturbing the baseline before and after the pulse the digital oscilloscope incorporates a pulse rejector The rejector al lows pulses to be displayed only if there is a clear period before and after each pulse The pile up reject window is dependent on the horizontal display size The probability of pulse pileup and the rejection rate is dependent on the Horizontal Scale setting and the Incoming Count Rate ICR As the count rate increases the digital oscilloscope will reject a larger percentage of the pulses processed by the instrument If the rejection rate becomes too high the scope may stop updating and the alarm message Invalid Data will be posted just below the Trigger Select box If the ICR is increased the Invalid Data alarm message may flash on and off as a warning that the high rejection rate threshold is being appr
107. s 98 will automatically prompt you for the USB driver diskette as part of its plug and play device architecture There is no need to re boot your system 4 Follow the steps in the Add New Hardware Wizard to add your new USB driver Use the default steps by clicking Next 5 Choose Search for the best driver for your device by clicking the Next button default 6 Select the check box for specify a location type your CDROM drive letter and specify the CIUSB directory on the CDROM 7 Click Next and Finish to complete the steps to install the USB driver It is not necessary to reboot The MID Wizard Note These steps are only required once i e when Windows 98 detects that new hardware has been added to your system or if the drivers are missing or need to be re installed Creating an MCA Input Definition The first step in using your DSA 1000 is to create an MCA Input Definition MID For most Genie 2000 based systems you 1l want to use the MID Wizard to help you set up your DSA 1000 s Input Definition quickly and easily If your Input Definition is more 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 18 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 3 lets you select the
108. s selected sets the minimum input acceptance level range is 0 to 100 INP POLARITY Selects either POSITIVE or NEGATIVE input polarity INH POLARITY Selects either Active High or Active Low Reset Preamp Inhibit po larity PUR GUARD Selects Guard Time GT multiplier 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 65 Specifications FDISC SHAPING Selects NORMAL or LOW ENERGY to optimize the fast discriminator shaping for the selected detector type NORMAL The Fast Discriminator shaping is optimized for Ge detectors and general gamma spectroscopy the fast discriminator filter rise time is set to 40 ns LOW ENERGY the Fast Discriminator filter rise time is set proportional to the slow shaping rise time selection FDISC MODE Sets the Fast Discriminator Threshold mode AUTO the threshold is optimized automatically above the system noise level MANUAL allows threshold to be adjusted manually FDISC SETTING Active when manual FDISC mode is selected sets the Fast Discriminator threshold level range is 0 to 100 the front panel ICR LED serves as a user aid when manually setting the Fast Discriminator threshold INHIBIT MODE Selects AUTO or MANUAL Reset Preamp Inhibit Modes dis ables pulse processing extends the system dead time reinitializes the pileup rejector and gates off the baseline restorer AUTO System is gated off for th
109. s to verify correct operation of the hardware The instrument s internal self di agnostics will activate the following indicators for approximately one second POWER FAULT High Voltage Level bar graph 1 3 kV 1 3kV 5 kV 5 kV HV Status LEDs and the DEAD TIME bar graph During power on diagnostics the FAULT LED is illuminated If the diagnostics were successful the POWER LED and one high voltage polar ity range indicator should remain active The FAULT LED will extinguish If during diagnostics a fault was detected the FAULT LED will remain on In addition the actions of the POWER and ACQ LEDs will aid with identifying the potential prob lem area A FAULT LED and blinking POWER LED indicates a problem with the ac adapter or signal processing logic A FAULT LED and blinking ACQ LED indicates a problem was detected with the microprocessor ram data memory loading the FPGA logic or FPGA communication After the self diagnostics completes or any time there after a FAULT LED in conjunc tion with a blinking HV LED indicates a HV Inhibit or high voltage power supply fault Spectroscopy System Setup Figure 25 shows a typical gamma spectroscopy system Perform the following steps to set up your spectroscopy system 1 Ifyou are using a detector with a reset preamp please refer to Operation with Reset Preamps on page 81 for specific instructions 42 Note Spectroscopy System Setup DSA 1000 Digital Desktop Spectros
110. son the scope is not triggered one of the error messages below will appear to help diagnose the problem Count Rate Too Low This message may appear if the Input Count Rate ICR is too low or the DSA 1000 is not connected to the detector or test pulser The Digital oscilloscope requires a minimum ICR of 40 cps to operate correctly Count Rate Too High This message may appear for the following conditions e The ICR is above 20 kcps The Fast Discriminator Mode is set to Manual and the Fast Discriminator Threshold is set too low into the noise For this condition the fast discriminator function is responding to noise producing an ICR rate above 20 The corrective action is to lower the count rate and or set the FDIC Mode to Auto or raise the FDIC Setting if using the Manual Fdisc Mode For information on setting up the Fast Discriminator please refer to the DSP Gain Parameters on page 31 Invalid Data This message may appear for the following conditions 39 Using the Digital Oscilloscope Function e ICR is between 40 cps and 20 kcps e Digital oscilloscope Horizontal Scale us div is set too long resulting in a high rejection rate due to excessive pileup For additional information on the scope pileup rejector please reference Scope Triggering and Pileup Rejector on page 41 for additional information The corrective action would be to reduce the ICR reduce the Scope Horizontal Scale setting or close the scope utility
111. ssist with parameter setup and to verify operation of the DSA 1000 The digital oscilloscope reconstructs the digital filter output signal which is filtered using a trapezoidal weighting function for view ing The waveform provided by the digital oscilloscope is similar to the waveform pro duced by a traditional spectroscopy amplifier when viewed on an analog or digital oscilloscope However the DSA 1000 digital oscilloscope contains built in averaging and rejection functions to reduce noise and pileup to improve waveform fidelity This makes it easier to perform necessary adjustments quickly and accurately The Digital Oscilloscope can be launched from the Pole Zero Assistant screen or the Gamma Acquisition and Analysis application s main toolbar The Pole Zero Assistant screen is active only if RC is selected as the Preamp Type in the MID Definition The Pole Zero Assistant screen is located on the second page of the MCA Adjust Filter screen as shown in Figure 23 C Stab C HVPS C Gain Filter gt Pole Zero Assistant zwo MA al B Bt Count rate too low Figure 23 Pole Zero Assistant Adjust Screen Click on the oscilloscope icon in the right top corner of the Pole Zero Assistant box to launch the oscilloscope function If Reset is selected as the Preamp Type in the MID Definition the pole zero compensation is automatically set to a value of zero rep resenting the matching required for a fall time
112. stics such as size noise characteristics and collection characteristics preamplifier and incoming count rate Settings for typical germanium coaxial detectors have been discussed above Below is a list of DSA 1000 rise time and flat top settings for other common detectors Detector Rise Time Flat Top us Scintillation Nal TD 0 8 0 2 or 1 2 0 6 Silicon Charged Particle PIPS 0 8 0 2 1 2 0 6 or 2 8 0 6 Proportional Counter 0 8 0 2 1 2 0 6 or 2 8 0 6 Lithium Drifted Silicon Si Li 18 4 1 2 or 36 2 4 Coaxial Germanium 2 8 0 6 or 5 6 0 8 Low Energy Germanium 5 6 0 8 18 4 1 2 or 36 2 4 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 1 on page 73 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 particular detector and application Pole Zero Matching Using the Digital Oscilloscope Flat Top Setting The DSA 1000 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 If the flat top is too short 1t may result in low side spectral tailing and degraded resolution However if these symptoms occur a
113. system setup For this case the scope can be minimized or hidden from view for either case the scope win dow is temporally removed from the Gamma Acquisition and Analysis GAA win dow to allow viewing of the spectral data and adjust screens When the scope window is maximized or restored to view it retains the setting that were last used If the scope application is open it can be hidden from view by clicking on the scope icon in the PZA adjust screen or the tool bar in the GAA window Clicking on the scope icon a second time will restore the scope window to view The scope window can also be minimized by clicking on the minimize button in the top right corner of the scope window When performed the scope window minimizes to a task bar the de fault location is at the lower left corner of the Windows Desktop To restore or close the scope window click on the appropriate button Note Clicking the scope icon will hide the scope application from view if the scope window was minimized the scope task bar will also be hidden from view Click on the icon again to restore the scope window or task bar Digital Oscilloscope Controls and Indicators The digital oscilloscope is adjusted using the following controls Refer to Figure 24 for the location of the controls Adjusting the vertical and horizontal sliding controls is accomplished by either clicking on and dragging the button or clicking in the button s travel area Vertical Scale Sets the
114. t high rates only the P Z setting may be misadjusted In this case first verify the correct P Z setting and readjust if necessary To set the flat top start with a long value then collect a spec trum and verify good resolution and peak symmetry Reduce the flat top and repeat the process Continue 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 throughput 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 manually checking the flat top setting if the rise time is increased or de creased 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 adjust the rise time to the desired value and set the flat top to zero Pole Zero Matching Using the Digital Oscilloscope At high count rates Pole Zero P Z matching adjustment is extremely critical for maintaining good resolution and low peak shift For precise and optimum setting of the P Z matching the digital oscilloscope can be used Please review Digital Oscillo scope Controls and Indicators on page 37 for information on setting up
115. t you are connected to This is done in the MID Definition please refer to The MID Wizard on page 13 for instruction on assigning COM ports and baud rates Using the USB Port 98 Connecting to the Host Computer The USB cable is 3 m 10 ft long it allows transfer of computer commands and spec tral data between the DSA 1000 and the host computer Both ends have USB connec tors which are defined by the USB standard one end is rectangular the other end is square Connect the square end of the USB cable to the USB port located on the rear panel of the DSA 1000 connect the rectangular USB connector of the cable to the USB port on the host computer When connecting to the computer using the USB port a hardware configuration must be created in the MID Definition The DSA 1000 device is uniquely identified using it s serial number The serial number is an 8 digit number that is affixed to the bottom of the instrument Please refer to The MID Wizard on page 13 for instruction on configuring the hardware for USB operation Connecting Multiple DSA 1000 s Most USB computers provide two host USB ports the ports are usually designated A and B Up to two DSA 1000 s can be supported with no additional hardware If more that two DSA 1000 s are to be connected to the same computer then a USB hub will be required Hubs are available that allow up to seven DSA 1000 s to be at tached For additional information on USB hubs pleas
116. tained using sources with a small number of peaks such as Co Cs or Co The Pole Zero Assistant operates properly with spectral peaks located within 25 to 100 of the MCA spectral range However best performance is obtained with the system gain adjusted to place the primary peaks within the top 75 to 95 of the MCA spectral range These recommendations also ap ply when adjusting the pole zero manually on systems when not using the Pole Zero Assistant Once completed replace the calibration source with the sample to be analyzed and adjust the system gain as required Adjustment Begin the adjustment by noting the Pole Zero Quality Indicator pointer position As previously mentioned the pointer position for proper pole zero is the meter null point or vertical line at the center of the meter range Using the indicator pointer and painted pointer history bar adjust the pole zero setting slider bar in the direction that brings the Quality Indicator pointer toward the target vertical center line The slider bar provides three levels of adjustment granularity Grabbing the thumb tab with the mouse allows you to drag the tab to the desired setting Clicking on the scroll box region between the slider box and the left right arrow buttons changes the pole zero setting by approximately 30 adjustment steps at a time Clicking on the left right arrow buttons increments the Pole Zero setting one adjustment step at a time Continue the adjustment until th
117. ted throughput is reduced as the Guard time and 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 59 PUR LTC Operation Trapezoid Signal gt Pile up Reject Interval m 1 PUR Guard at X1 1 Pile up Reject Interval extended by PUR Guard gt X1 1 Figure 28 PUR Reject Interval 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 evident by a short lived undershoot or ring on the trailing edge of the shaped signal see Figure 29 Figure 29 Preamplifier Secondary Time Constant 60 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
118. th If using a reset type of preamp connect the Preamp s Reset Inhibit Signal to the DSA 1000 RESET Input using a RG62 U coax cable If the detector is equipped with an LN monitor connect the detector s HV Inhibit sig nal to the DSA 1000 HV INH input Connect the detector s preamp output to the DSA 1000 AMP IN connector using a RG62 U coax cable Connect the HV output of the DSA 1000 to the detector using a RG59B U high volt age coax cable Canberra part number C123 X where x denotes the cable length For additional information please reference Chapter 6 Basic Spectroscopy Operation Grounding the System It s not necessary to ground the DSA 1000 system in most applications However in extreme environmental conditions the DSA 1000 might be susceptible to oscillations or noise due to ground loops radio frequency interference RFI or electromagnetic interference EMI When grounding the DSA 1000 is required a ground connector can be attached to bottom left screw on the rear panel A ground connection at this point makes positive electrical contact with both circuit and chassis ground Using a spade lug simplifies the operation since the screw does not require complete removal it only needs to be loosened Power On Power On When the DSA 1000 is first turned ON it will go through an initialization and self test process During the initialization period the DSA 1000 will run internal diagnostics routines to veri
119. th some undershoot while Figures 35 and 36 show under and over compensation of the preamplifier decay time constant Oscilloscope Digital Oscilloscope Vertical Scale Vertical Offset Pole Zero Matching Using the Digital Display Options F Zoom On W Grid Lines Trigger Select e Fast Discriminator Inhibit Smoothing Factor a Horizontal Scale Horizontal Delay 20 0 8 0 L Hr Figure 34 M Digital Oscilloscope Vertical Scale 0 005 Vertical Offset I f uf Defaults 0 5 microseconds div 100 microseconds Exit Correct Pole Zero Using a Nal TI Detector Display Options F Zoom On W Grid Lines Trigger Select e Fost Discriminator Inhibit Smoothing Factor Horizontal Scale Horizontal Delay 20 0 8 0 L ul 32 if Defaults 05 microseconds div 100 0 microseconds Figure 35 Undercompensated Pole Zero Using a M Digital Oscilloscope Vertical Scale 0 005 volts div 24 0 005 Vertical Offset Smoothing Factor Nal Tl Detector Display Options T Zoom On W Grid Lines Trigger Select e Fest Discriminator Inhibit Horizontal Scale Horizontal Delay 200 8 0 H Defaults microseconds div 100 0 microseconds Figure 36 Overcompensated Pole Zero Using a Nal Tl Detector 79 Performance Adjustments For the examples in Figures 34 through 36 the DSA 1000 Filter settings of 1 2
120. 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 40 rise fall times ranging from 0 4 to 38 Us 33 User Interface and Controls Y Adjust C Stab O HYPS C Gain Figure 21 Adjust Screen s DSP Filter Settings 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 The flat top time can be selected from 21 flat top selections ranging from 0 to 3 us 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 Pole Zero Assistant The Pole Zero Assistant Adjust screen Figure 22 is on the second page of the DSP Filter parameters select Next after opening the Adjust Screen to get to the second page Y Adjust C Stab C HYPS C Gain Filter Pole Zero Assistant zo M al sl Count rate too low Figure 22 Pole Zero Assistant Adjust Screen Note The Pole Zero Assistant screen is available only if RC is selected as the Preamp Type in the Settings DSP Filter Device of the MID Definit
121. the spectrum display and analysis parame ters Three choices are available Ge Nal or Alpha For additional information please refer to Genie 2000 documentation 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 26 Saving and Loading the Input Definition 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 disconnected 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 and Loading the Input Definition Having completed a definition the next step is to save it in a disk file so it can be used in the future From the File menu the command Save As saves the definition to a user defined MID file and the command Save saves the settings to an exisiting MID file After having saved the definition the next step is to load it into the run time database so t
122. tor a slider bar to adjust the pole zero setting a four digit readout indicating the current pole zero setting and a Digital Oscilloscope icon for launching the Digital Oscilloscope function If the input count rate is either too low or too high for the Pole Zero Assistant to function correctly a text message in dicating the condition will appear beneath the Quality Indicator Refer to Figure Note The speed of the Pole Zero Assistant PZA measurement may be reduced when MCA Acquire is set ON For optimal speed performance it is recom mended that MCA Acquire be set OFF The PZA measurement speed may also be somewhat slower when the Digital Oscilloscope is open The scope and PZA operate properly when both are open however the PZA measurement may be slower when the scope is open Minimizing or closing the scope appli cation will optimize the PZA measurement speed Detector Matching Pole Zero Adjustment Setup Adjust the Co radioactive source for an incoming count rate ICR between 40 counts second and 20 k counts second The Pole Zero Assistant may fail to operate properly if the incoming count rate is not within this range The incoming count rate can be verified by reading the ICR value on the MCA Status Page of the Gamma Acquisition and Analysis window Select Update to obtain a new ICR reading whenever the radioactive source is adjusted Note Although any radioactive source may be used the most accurate adjustment is ob
123. 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 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 optimized 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 1 lists the DSA 1000 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 1 Gaussian Shaping vs Throughput and Resolution Gaussian Shaping cn aimara mos 0 5 us 0 8 us 0 2 us 1 2 us 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 36 us 2 4 us Note 1 Optimized for high t
124. trols mece arses teak Go Sea A ie OSG A ee A Rk wens aa 65 A ch ee mii ey ages e gee ha AR he hk we ae SG Me mt a He a E 66 Digital Oscilloscope ss ab Bo oe ae Re oe ee ee ee a 67 HVPS ieee debe eRe eee ew ES Re KE OSS HER RE DE ee ee Oe eee 67 Stabilize eo sess ew RG ee a eee a eo a a A 68 MES dass a ee OR eS Bh ee a ee ee Be PAE se 68 Programmable Settings sea ego ecap a dei Ee ee 68 Performan re sgt rate aes Gre a da nd al ad ae aa 69 Signal PTOCESSIDS s oepa maene a A ara e iie ARA A 69 Pileup Rejection Live Time Correction o o 69 ACQUISII ON s age de a YG Se ek Be we ee a eee 2 69 HVPS 8b 442 SPR REE PESOS SEES HEADER Ew EL Eh RR ORE ERE OH 70 GABLES boc do heey oe ke he A a che wa he wet e itd Oy E 71 Environmental s se se corea Bee ae eee eS a OE eae DER ee De 71 Physical urinaria Y Be a bee ee ee ee 71 Ordering Information s s cos 2h be bok MEA ee ae BP ee Se oS 71 Performance Adjustments 72 Rise Time and Flat Top Adjustments 2 2 2 0 000 000 000 e ee eee 72 Pole Zero Matching Using the Digital Oscilloscope o o oo e 75 Using a Ge Detector Co Source and Digital Oscilloscope o o o 76 Using a Nal Tl Detector Co Source and Digital Oscilloscope 78 Baseline Restorer soe saa Ge A A A e 80 Manual Fast Discriminator Threshold o o 80 Operation with Reset Preamps o s sostas aoa aoa ee 81 Configurin
125. tton 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 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 count 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 Correction Rng Correction range Ge 1 or Nal 10 This control selects the Gain Correction range that can be provided to correct for drift Select Ge for a german
126. ual It is recommended that the high voltage setting be verified prior to turning the high voltage power supply to ON CAUTION Excessive voltage and or incorrect polarity can permanently damage the detector system 7c HV Settings Range Sets the HV Range to match the configuration of the high voltage power supply and requirements 45 Basic Spectroscopy Operation 46 Voltage Limit Voltage Inh Signal of the intended detector The choices are 5000 1300 1300 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 The voltage settings can also be typed in from the keyboard then accepted with the OK button within the control Sets the polarity of the HV Inhibit input All Canberra detectors and preamps use the Positive setting For additional information please refer to High Voltage Settings in the MID Definition and Appendix A Specifications There are many other parameters that can be adjusted in the MID Definition 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 a
127. with Reset Preamps on page 81 for additional information Note Once the Pole Zero is optimized for the intended detector the digital filter shaping parameters Rise Time and Flat Top can be changed as required with out the need to make further Pole Zero adjustments However the Pole Zero compensation must be readjusted if the detector is changed Detector Matching Pole Zero Matching using the Pole Zero Assistant Pole zero matching is adjusted manually using a slider bar located on the Pole Zero Assistant screen Figure 26 The Pole Zero Assistant and Digital Oscilloscope are provided as user aids for optimizing the pole zero setting For more information on pole zero adjustment using the Digital Oscilloscope function please refer to Pole Zero Matching Using the Digital Oscilloscope on page 75 Quality Indicator Count rate too low Figure 26 Pole Zero Assistant Screen The Pole Zero Assistant measures and analyzes the tail of the trapezoid signal and pro vides visual feedback showing the quality of the pole zero adjustment via a simulated null meter or Pole Zero Quality Indicator The center of the indicator marked with a vertical centerline serves as the target when adjusting the pole zero The pole zero is optimally set when the pointer and the target centerline null point are aligned The Quality Indicator pointer indicates the quality of the current pole zero setting The area to left of the target null point a
128. ws adjustment of the HVPS output over the voltage range selected by the HV module configuration and voltage limit selections HVPS RESET Resets a power supply fault after a fault condition has occurred INH SIGNAL Sets the polarity sense of the High Voltage Inhibit input Positive set ting for all Canberra preamplifiers Enable condition cold detector is an open circuit or active high gt 1 2 V to 24 V Inhibit condition warm detector is 24 V to lt 1 2 V or ground Negative setting all preamplifiers and LN monitors where enable condi tion cold detector is 24 V to lt 1 2 V Inhibit condition warm detector is open cir cuit or active high 2 1 2 V to 24 V With Negative selected an open input will disable the high voltage 67 Specifications Stabilizer MCS GAIN MODE ON OFF HOLD ON OFF enables or disables the Gain Mode HOLD disables the stabilizer 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 Rate Div 1 to 16 Correction Range of 1 for Ge and 10 for Nal detectors MODES TTL Integral ROI Discrimination Events are counted for the duration of a programmed number of sweeps Each SWEEP incorporates a programmed number of channels Each channel represents a DWELL duration TTL TTL pulses counted from MCS IN connector Integral Total gamma events counted from DSP spectrum ROI Dis
129. y shaping processing time and with pole zero properly set Pileup Rejection Live Time Correction PULSE PAIR RESOLUTION Better than 500 ns with NORM Detector Type se lected DEAD TIME CORRECTION Extended live time correction accuracy of reference peak area changes 5 3 typical at up to 50 system dead time with a setting of 5 6 Us rise time and 0 8 us flat top Acquisition DATA MEMORY GROUPS 1 16K PHA Channels or 2 8K PHA channels sin gle mode only 28 bits per channel 10 year data retention power loss Divisible into halves quarters eighths and sixteenths 2 8K MCS channels 28 bits per channel 10 year data retention power loss STORAGE MODE PHA or MCS 69 Specifications Note Simultaneous operation of PHA MCS is not supported PRESET MODES PHA Mode Live or True Time Counts in single channel Counts in ROI Counts in multiple ROIs MCS Mode Sweeps Count greater or equal to preset Counts Count greater or equal to preset ROI Counts TIME RESOLUTION 0 01 s live and true time PRESET TIME 1 to gt 4 x10 s PRESET SWEEPS 1 to 65 535 HVPS 70 Plug in programming modules select the maximum voltage range and polarity The ac tual HV range and polarity is displayed on the front panel and reported by the soft ware 1300 Volt Range 10 V to 1300 V or 10 V to 1300 V dc at 300 WA 5000 Volt Range 1300 V to 5000 V de or 1300 V to 5000 V dc at 20 uA ADJUSTMENT RESOLUT

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