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Neutron Gamma Discrimination in Agata

Neutron Gamma Discrimination in Agata. A.Ataç, A. Kaşkaş, S. Akkoyun, M. Şenyiğit, T. Hüyük, O.Kara and J. Nyberg. Possibility of discriminating neutrons and gammas by tracking Identify the neutron interaction points in Agata detectors Find a ‘pattern’ for neutron interactions.

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Neutron Gamma Discrimination in Agata

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  1. Neutron Gamma Discrimination in Agata A.Ataç, A. Kaşkaş, S. Akkoyun, M. Şenyiğit, T. Hüyük, O.Kara and J. Nyberg Possibility of discriminating neutrons and gammas by tracking Identify the neutron interaction points in Agata detectors Find a ‘pattern’ for neutron interactions NIM A, in print Aim: Reducing the background in the γ – ray spectra Agata as a neuton detector ?

  2. Cross-sections for the n + natGe reaction● elastic scattering natGe (n,n)● inelastic scattering natGe (n,n´γ) Inelastic scattering J. Ljungvall, J. Nyberg, NIM A546 (2005)553 J. Ljungvall, J. Nyberg, NIM A550 (2005)379

  3. Method 1) Simulations Geant4 with AGATA geometry J. Allison et al. NIM A506(2003)250. E. Farnea, D. Bazzacco LNL Anual Report 2003, p.158. J. Ljungvall, J. Nyberg, NIM A546 (2005)553. Geant4 correction, pulse-height defect (PHDEF) 2) Tracking MGT code, D. Bazzacco ---------------------------------------------------- First step:1 MeV neutrons on 74Ge (with and without PHDEF) 596 keV from the center of Agata Methods:• small energy deposition produced by neutrons • direction of the gammas • Figure of Merit (FM) values 1208 596 0 74Ge Second step:1 – 5 MeV neutrons on natGe Mn = 6, Mγ = 10 Eth = 5 keV, trigger threshold = 50 keV Number of neutrons 0 10 Neutron Energy (MeV)

  4. Recoil Energyinelastic scattering of 1- 5 MeV neutrons on natGe no phdef phdef 1 MeV 2 MeV 3 MeV 4 MeV 5 MeV counts

  5. 1 MeVneutrons on 74Ge, no phdef n = 6 65 keV Tracking –mgt • clustering • FM values n = 5 n = 4 n = 3 n = 2 596 keV n = 1

  6. Method 1: Energy of the first and second interaction pointsNeutrons and gammas on 74Ge 1 MeV neutron Efirst n = 2 - 6 596 keV gamma Esecond n = 3 - 6 1 MeV neutron counts 596 keV gamma Energy (keV)

  7. θgfrom the position of the interaction points θc from Compton formula Method 2:θg – θc n > 2 1 MeV neutron θg = θc 15 596 keV gamma n > 2

  8. Method 3: Figure of Merit (FM)

  9. Reduction in %1 MeV Neutrons on 74Ge, Eth = 5keV, no phdef II Gates I GatesII

  10. 596 keV line with and without PHDEF1 MeV Neutrons on 74Ge, Eth = 5keV 596 keV phdef counts nophdef bump Eγ (keV)

  11. Gamma-ray energy spectra after tracking (mgt)Neutrons on 74Ge, phdef 1204 608 5 MeV 596 596 596 608 0 74Ge 596 3 MeV 608 counts 596 2 MeV 608 596 1 MeV Eγ (keV)

  12. Gamma-ray energy spectrum after tracking (mgt)Flat distribution on 1 –5 MeV neutrons on natGe, phdef 834 keV counts No gates With gates Gates I Gates II Eγ (keV)

  13. The neutron rejection methods were tested on a case where 6 neutrons with energies between 1 to 5 MeV were emitted in coincidence with a cascade of 10 rays.

  14. At Eγ = 1MeV, PTB is ratio is increased by a factor of 2.4 and the ε is reduced by a factor of 1.25 for gates II. RPTB = PTB / PTB(after neutron rejection) Rε = ε / ε (after neutron rejection) Gates I Gates II

  15. Conclusion and Future Plans We identified the γ-rays produced by neuton inelastic scattering on Ge isotopes by checking its direction, FM value and by the small energy it deposits in the detector. The neutron rejection methods were also tested on a case where 6 neutrons with energies between 1 to 5 MeV were emitted in coincidence with a cascade of 10 rays. As a result, at a gamma-ray energy of 1 MeV, the suggested gate set increases the PTB value by a factor of 2.4, whereas the photopeak efficiency is reduced by a factor of 1.25. •En > 5MeV isbeing studied. For Giant Resonance studies • An experiment with AGATA detectors by using a 252Cfsource and BaF2 detector for TOF selection of neutrons.  Menekşe’s talk

  16. Number of interaction points in Ge after tracking n' 596 keV gamma n 596 keV gamma Counts 596 keV gamma 1 MeV neutron Number of interaction points

  17. Gamma-ray energy spectrum after tracking (mgt)Flat distribution on 1 –5 MeV neutrons on natGe, phdef Number of neutrons 0 10 Neutron energy (MeV) 596 keV, 74Ge 834 keV, 72Ge counts 1039 keV, 70Ge 608 keV, 74Ge Eγ (keV)

  18. Hittites 1650 - 1200 BC Anakara U: A.Ataç, A. Kaşkaş, S. Akkoyun, M. Şenyiğit, T. Hüyük, O.Kara Uppsala U: J. Nyberg Ceremonial Standard

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