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Neutron Gamma Discrimination in Agata

Neutron Gamma Discrimination in Agata. Ay ş e Ata ç. Possibility of discriminating neutrons and gammas by tracking Identify the neutron interaction points in Agata detectors Find a ‘pattern’ for neutron interactions. Aim : Reducing the background in the γ – ray spectra

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Neutron Gamma Discrimination in Agata

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  1. Neutron Gamma Discrimination in Agata Ayşe Ataç Possibility of discriminating neutrons and gammas by tracking Identify the neutron interaction points in Agata detectors Find a ‘pattern’ for neutron interactions 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 ---------------------------------------------------- 1208 First step:1 MeV neutrons on 74Ge (with and without PHDEF) 596 keV from the center of Agata Criteria:• small energy deposition produced by neutrons • direction of the gammas 596 0 74Ge Second step:1 – 5 MeV neutrons on natGe Eth = 5 keV Mn, Mγ = 1 Number of neutrons 0 10 Neutron Energy (MeV)

  4. 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

  5. Recoil Energyelastic scattering of 1- 5 MeV neutrons on Ge isotopes JENDL 1 MeV 2 MeV 3 MeV 4 MeV 5 MeV counts Ge recoil energy Erec (keV)

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

  7. Gamma-ray spectra after tracking (mgt)1 MeVneutrons on 74Ge, no phdef bump 1208 596 n = 6 596 0 n = 5 74Ge n = 4 n = 3 n = 2 596 n = 1 n = number of interaction points

  8. 1 MeVneutrons on 74Ge, no phdef n = 6 80 keV n = 5 n = 4 n = 3 n = 2 596 keV n = 1

  9. Criteria 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)

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

  11. θg - θc n = 6 n = 5 n = 4 n = 3 n = 2 n>1

  12. total peak 596 keV bump 596 keV gamma θg - θc 41 23 63 11 efirst 38 5 62 6 θg – θc or efirst 50 26 75 15 θg – θc or efirst or esec. 57 35 88 23 Reduction in %1 MeV Neutrons on 74Ge, Eth = 5keV, no phdef No conditions With conditions 596keV counts bump Eγ (keV)

  13. 596 keV line with and without PHDEF1 MeV Neutrons on 74Ge, Eth = 5keV 596 keV phdef counts nophdef bump Eγ (keV)

  14. total peak + bump 596 keV 596 keV gamma θg - θc 26 31 11 efirst 5 6 1 θg – θc or efirst 26 31 11 θg – θc or efirst or esec. 28 33 12 Reduction in % 1 MeV Neutrons on 74GePHDEF, Eth = 5keV 596keV counts No conditions With conditions Eγ (keV)

  15. 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)

  16. 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)

  17. total peak 834 keV bump 1 MeV gamma θg - θc 32 24 51 10 efirst 10 - 37 1 θg – θc or efirst 34 25 56 11 θg – θc or efirst or esec. 38 28 69 14 Gamma-ray energy spectrum after tracking (mgt)Flat distribution on 1 –5 MeV neutrons on natGe, phdef 834 keV counts No conditions With conditions Eγ (keV)

  18. Conclusion and Future Plans We identified the γ-rays produced by neuton inelastic scattering on Ge isotopes by checking its direction and by the small energy it deposits in the detector. For En = 1-5 MeV, if the recoil energy is included in a cluster during tracking, we can eliminate 69% of the background with a loss of 14 % in good γ-rays from the target place. •We may improve the results by doing the selection during the tracking! • Mn > 1 should be studied. • An experiment with AGATA detectors by using a 252Cf source, BaF2 and plastic detectors for TOF of the neutrons.

  19. 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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