A Comparison of Analog and Digital Pulse-Shape-Discrimination Systems … · 2019. 9. 10. · FOM =...
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FOM = 0.90 FOM = 1.05 Ratio (tail/total) TAC (volts) A Comparison of Analog and Digital Pulse-Shape-Discrimination Systems for Organic-Liquid Scintillators Charles Sosa (PhD Candidate), Dr. Marek Flaska and Dr. Sara Pozzi Department of Nuclear Engineering & Radiological Sciences, University of Michigan, Ann Arbor, MI 48109 • Pulse-shape-discrimination (PSD) systems can used with some scintillators to discriminate between neutrons and gammas • The motivation behind this work is to quantify the best PSD system that most accurately discriminates • The PSD performance of a digital, charge- integration PSD system (CAEN V1720) is compared against an analog, zero- crossing PSD system (Mesytec MPD-4). • Measurements were performed using an organic liquid scintillator (EJ-309) coupled with a photo-multiplier tube (ETL-9821B). • A Cf-252 spontaneous-fission source was used to provide neutrons and gammas. • Figures of merit (FOM) were used to assess and compare the performance of the PSD systems • Under the measurement constraints, digital PSD system out-performed analog PSD by approximately 15%. Project Overview Measurement Results Figure.3: Comparison of analog (left column) and digital (right column) PSD plots, with the PSD images shown in the top row and PSD separation images shown in the bottom row. Analog PSD separation was done using a histogram of TAC values while digital PSD separation was done using a histogram of the ratio values (i.e., tail to total integral values) Background AMPL = Fast component (20 ns integration window) Before 6 th order Filter After 6 th order Filter (assists discrimination) Ref: A. Ruben et al., A New Four Channel Pulse Shape Discriminator, (2007) Total Integral Tail Integral Voltage Time Digital Method Organic scintillator Pulse (artistic rendition) Analog Method TAC = time at zero crossing NDIS (green) for Triggering purposes Figure.1: Digital charge integration PSD Figure.2: Analog zero-crossing PSD Experimental Procedure • MPD-4 settings were optimized in order to produce the best possible PSD performance (table 1) using the following FOM equation: Parameter Value Range WALK (influences curvature of clusters at low energies) 100 (default) [50,150] THRESHOLD (serves as an energy cut-off) 0 [0,255] GAIN (influences curvature of clusters at high energies) 0 [0,15] QWIN (affects walk parameter, manual suggests to avoid adjusting) 100 (default) [0,200] NDIS (moves TAC values up and down for discrimination purposes in fast mode (0.91V)) 183 [0,255] Table.1: MPD-4 Settings (grayed rows not used) Future Work Acknowledgements This work was supported by the National Science Foundation and the Domestic Nuclear Detection Office of the Department of Homeland Security through the Academic Research Initiative Award # CMMI 0938909. FOM = Distance between gamma and neutron peaks FWHM gamma + FWHM neutron • The V1720 outperformed the MPD4 by 15% and future work will include using a larger dynamic range (8V instead of 2V)
Transcript of A Comparison of Analog and Digital Pulse-Shape-Discrimination Systems … · 2019. 9. 10. · FOM =...
FOM = 0.90 FOM = 1.05
Ratio (tail/total)TAC (volts)
A Comparison of Analog and Digital Pulse-Shape-DiscriminationSystems for Organic-Liquid Scintillators
Charles Sosa (PhD Candidate), Dr. Marek Flaska and Dr. Sara PozziDepartment of Nuclear Engineering & Radiological Sciences, University of Michigan, Ann Arbor, MI 48109
• Pulse-shape-discrimination (PSD) systemscan used with some scintillators todiscriminate between neutrons andgammas
• The motivation behind this work is toquantify the best PSD system that mostaccurately discriminates
• The PSD performance of a digital, charge-integration PSD system (CAEN V1720) iscompared against an analog, zero-crossing PSD system (Mesytec MPD-4).
• Measurements were performed using anorganic liquid scintillator (EJ-309)coupled with a photo-multiplier tube(ETL-9821B).
• A Cf-252 spontaneous-fission source wasused to provide neutrons and gammas.
• Figures of merit (FOM) were used toassess and compare the performance ofthe PSD systems
• Under the measurement constraints,digital PSD system out-performed analogPSD by approximately 15%.
Project Overview Measurement Results
Figure.3: Comparison of analog (left column) and digital (right column) PSD plots, with the PSD images
shown in the top row and PSD separation images shown in the bottom row. Analog PSD separation was done
using a histogram of TAC values while digital PSD separation was done using a histogram of the ratio values
(i.e., tail to total integral values)
Background
AMPL = Fast component(20 ns integration window)
Before 6th
order FilterAfter 6th order Filter
(assists discrimination)
Ref: A. Ruben et al., A New Four Channel Pulse Shape Discriminator, (2007)
Total Integral
Tail Integral
Voltage
Time
Digital Method
Organic scintillator Pulse (artisticrendition)
Analog Method
TAC = time at zero crossing
NDIS (green) for Triggering purposes
Figure.1: Digital charge integration PSD Figure.2: Analog zero-crossing PSD
Experimental Procedure
• MPD-4 settings were optimized in order toproduce the best possible PSD performance(table 1) using the following FOM equation:
Parameter Value Range
WALK (influences curvature of clusters at low energies)
100 (default)
[50,150]
THRESHOLD (serves as an energy cut-off) 0 [0,255]
GAIN (influences curvature of clusters at high energies)
0 [0,15]
QWIN (affects walk parameter, manual suggests to avoid adjusting)
100 (default)
[0,200]
NDIS (moves TAC values up and down for discrimination purposes in fast mode (0.91V))
183 [0,255]
Table.1: MPD-4 Settings (grayed rows not used)
Future Work
AcknowledgementsThis work was supported by the National ScienceFoundation and the Domestic Nuclear Detection Office ofthe Department of Homeland Security through theAcademic Research Initiative Award # CMMI 0938909.
FOM =Distance between gamma and neutron peaks
FWHMgamma + FWHMneutron
• The V1720 outperformed the MPD4 by 15% and future workwill include using a larger dynamic range (8V instead of 2V)
