1、qIntroductionqHardware SystemqData Processing SoftwareqTest and PerformanceqSummary and Prospects22022-7-232Measuring-decay radionuclides radioactivity4-coincidence counting and efficiency extrapolation method Traditionally,analog plug-ins:one measurement one coincidence resultDigital way:one measur
2、ement unlimited groups of coincidence resultThe system is developed for National Institutions of Metrology(NIM)of China32022-7-232022-7-234-decay radioactive sourcePb shield4 proportional counter(PC)Photomultiplier Pre-amplifier and shaping amplifier Multi-channel DAQ deviceData processing software2
3、022-7-235Front-End SubsystemDAQ SubsystemFront-End Subsystem2022-7-236CANBERRA Model 2006 Proportional Counter PreamplifierCANBERRA Model 2026 Shaping Amplifier ORTEC 572A Shaping Amplifier HAMAMATSU CR160 photomultiplier 2022-7-237DAQ DeviceBased on PXI platformConsists of five 3U size module cards
4、One Time Synchronize Card(TSC)generates clock and synchronize signal for other moduleTwo High Speed Acquisition Cards(HSAC)with two 8-bit 500MSPS DAQ channels per cardTwo Normal Speed Acquisition Cards(NSAC)with two 16-bit 62.5MSPS DAQ channels per cardThe slot0 system controller configures each mod
5、ule card and accepts data from them via PCI bus2022-7-238DAQ ControllingUsing WinDriver for driver developmentControlling and Monitoring the whole DAQ procedureOff-line Data ProcessingDeveloped with C+and Microsoft Foundation Class(FMC)Pulse peak finding moduleData conversion moduleDead-time process
6、ing moduleMulti-channel coincidence moduleEfficiency Extrapolation module 2022-7-239Measurement Theory2022-7-2310Simplified Processing Procedure Data conversion procedureDead-time processing procedureExtract pules features and pack them in unified format.Every element in the pulse feature sequence o
7、nly contains arrival time,rise time and the pulse amplitudeSimulate the dead-time losses of the real measurement system under the different triggering thresholds and dead-time situations2022-7-2311Redraw pules waveformDraw energy and delay-time spectrums Deadtime analysisCoincidence countingTwo kind
8、s of efficiency extrapolation Obtain absolutely radioactivityMulti-thread CPU and GPU computing 2022-7-2312radioactive source:60CoHalf-life value:5.26 yearsReference radioactivity:4686.6 Bq 2022-7-2313Relative errorJust 0.40%2022-7-2314Test result indicates that this system works well in absolute de
9、termination of radioactivity of-decay radionuclides such as 60Co and 59Fe.This work is going to be published on TNS.Under the support of researchers in NIM China,we developed an absolutely radioactivity measurement system for-decay radionuclides using 4-coincidence counting method.This system is the first digital 4-coincidence counting system of NIM China.In the future,we will focus on the development of digital liquid scintillation measurement system
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