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Investigate the possibilities of discriminating neutrons and gamma rays using tracking methods and various conditions. Test experiment with AGATA triple cluster, 252Cf source, and BaF2 detector. Simulation results and analysis.
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AGATA Demonstrator Test With a 252Cf Source: Neutron-Gamma Discrimination Menekşe ŞENYİĞİT
Investigation the possibilities of discriminating neutrons and gamma rays are important ! Methods for neutron-gamma discrimination with tracking: • The energy deposited in the first and second interaction points; • The difference in incoming direction of the gamma ray ; • Selection based on the FM value
To check our methods, we consider an experiment with AGATA triple cluster , 252Cf source and BaF2 detector. BaF2 detector is used for timing. Test period is about 3-4 hours. BaF2 60Co source 252Cf source Lead Shield ( cm3) Loss in gammas ~92-99% Loss in neutrons ~47-50% AGATA single cluster
Counts Neutron Energy (MeV) Simulations Simulations Geant4 with AGATAtriple cluster • Simulated data: • About 1 MeV -rays • Neutrons emitted from 252Cf source with 2.95 Ci (at LNL) Tracking with MGT code
Gamma-ray energy spectrum after tracking (mgt) counts Eγ (keV) • Neutrons emitted from 252Cf source with PHDEF • Distance between lead shield and AGATA triple clusteris 60 cm Number of events: 35046000 Neutron multiplicity: 4 Run time: 3 hours Tracking efficiency for gammas: 0.97
Gamma-ray energy spectrum after tracking (mgt)* Neutrons emitted from 252Cf source with PHDEF and 1 MeV -rays* Distance between lead shield and AGATA triple cluster is 60 cm total peak 834 keV bump 1 MeV gamma 834 keV No conditions θg - θc 43 25 61 10 With conditions Efirst 17 3 45 1 θg – θc or Efirst 46 26 69 11 θg – θc or Efirstor Esecond or FM 57 43 85 19 834 keV, 72Ge counts Eγ (keV)
-rays Neutrons Time of Flight Spectra for 70 cm • In this experiment we would also like to use the TOF technique in order to know when a neutron is hitting detectors to check how succesful our methods are. • One problem is that one don’t know the time resolution of the AGATA detectors. • Without PSA, it may be around 10 ns but this may be reduced very much by the PSA. • Time resolution is energy dependent. Counts TOF
-rays -rays -rays Neutrons Neutrons Neutrons Time Resolution Since we don’t know what the time resolution will be for AGATA detectors, we made TOF simulations by using different resolution values. Counts Counts Counts TOF, Time resolution = 5 ns TOF, Time resolution = 1 ns TOF, Time resolution = 3 ns
-rays -rays Neutrons Neutrons Counts Counts TOF, Time resolution = 10 ns TOF, Time resolution = 15 ns
Conclusions • We developed 3 methods for neutron-gamma discrimination by using tracking. We would like test these methods in a real test experiment where we shall use a 252Cf neutron source, one triple Agata detector and a BaF2 detector for timing. • We made some simulation in order to check the effect of our methods. • We checked the effect of different time resolution. • We are preparing a proposal for this test experiment which can be run just after the summer.