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Monte Carlo simulation of liquid scintillation neutron detectors: BC501 vs. BC537

Monte Carlo simulation of liquid scintillation neutron detectors: BC501 vs. BC537. J.L. Tain tain@ific.uv.es Instituto de Física Corpuscular C.S.I.C - Univ. Valencia. 1keV. 1MeV. BC537 as low neutron sensitivity -ray detector.

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Monte Carlo simulation of liquid scintillation neutron detectors: BC501 vs. BC537

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  1. Monte Carlo simulation of liquid scintillation neutron detectors: BC501 vs. BC537 J.L. Tain tain@ific.uv.es Instituto de Física Corpuscular C.S.I.C - Univ. Valencia

  2. 1keV 1MeV BC537 as low neutron sensitivity -ray detector State of the art detectors for (n,) measurements using the Pulse Height Weighting Technique at time-of-flight facilities (n,n) (n,) C6D6 detectors at n_TOF-CERN

  3. BC501 BC537 Motivation: En=2.5MeV 102.5cm !? En=4.3MeV From S. Williams (TRIUMF) : (@ Warsaw, Oct 2007) DESCANT: DEuterated SCintillator Array for Neutron Tagging

  4. BC501/NE213 liquid scintillators 5cm5cm C1H1.212  = 0.874g/cm3 n (@425nm) = 1.53  = 3.2 (32.3, 270) ns NIMA476 (02) 132 Mono-energetic neutron response 255cm

  5. n A min Neutron scattering s-wave (l=0) elastic scattering: Energy-momentum conservation: Isotropic in CMS: There is a minimum neutron energy (maximum recoil energy) after the collision, A dependent: 1-: H (1.0), D(0.89), C(0.28), Fe(0.069), Pb(0.019)

  6. 1H 2H CM system ELASTIC SCATTERING ANGULAR DISTRIBUTION 12C 208Pb

  7. Angular distribution in the LAB reference frame 1H En = 1MeV 2H En = 5.5MeV

  8. Monte Carlo simulations of liquid scintillation neutron detectors • General purpose codes: GEANT3, Geant4,… and specific codes: NRESP, SCINFUL, … ENDF/B-VII.0 • Requires nuclear reaction data (missing information on 12C(n,n3), …) • Requires material response (light production, …)

  9. Luminescence in organic materials The non-radiative transfer mechanism between excited centers induces an energy-loss dependent light production … … and a varying time distribution Several time components

  10. Light production curves: p, , 12C in NE213: Dekempeneer et al. NIM A256 (1987) 489 d in NE230: Croft et al. NIM A316 (1992) 324 Simulations with GEANT3/GCALOR  (In reality there is some dependence on chemical composition, fabrication, age, …) (assumed same  and 12C light curves in BC501 & BC537)

  11. (10x10cm)

  12. “ENERGY CALIBRATION”

  13. CONCLUSION: !? Neutron interaction time t=5ns: C6D6: 98.3% BC501: 95.6% C6D6 =12.2% BC501=17.7% (Eth=100keVee)

  14. Does the use of C6D6 diminishes the cross-talk? • Simulation: • cluster of 7 hexagonal detectors • diameter: 15 cm • length: 5 cm and 15 cm • maximal illumination of central detector • source at 1 m • neutron energies: 1 MeV and 5 MeV

  15. Eth=100keV En = 1 MeV En = 5 MeV

  16. Eth=100keV En = 1 MeV En = 5 MeV

  17. Ratio of counts scattered to outer detectors respect to central detector in the energy window [Emax/2,Emax] 15cm15cm En = 1 MeV En = 5 MeV

  18. Conclusion: The use of deuterated scintillators does not seem to represent an advantage with respect to hydrogenated scintillators in order to reduce the inter-module neutron scattering

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