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LIGHT-OUTPUT SIMULATIONS FOR NEDA Andrea Gottardo Università di Padova

LIGHT-OUTPUT SIMULATIONS FOR NEDA Andrea Gottardo Università di Padova. “ Universa Universis Patavina Libertas ”. Plan of presentation. Introduction : The importance of light-output response in scintillators Calculations for light-output produced by neutrons Light-output spectra

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LIGHT-OUTPUT SIMULATIONS FOR NEDA Andrea Gottardo Università di Padova

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  1. LIGHT-OUTPUT SIMULATIONS FOR NEDA Andrea Gottardo Università di Padova “Universa Universis Patavina Libertas” NEDA meeting

  2. Plan of presentation • Introduction : The importance of light-output response in scintillators • Calculations for light-output produced by neutrons • Light-output spectra • First estimations of efficiency and cross-talk for NEDA • Conclusions NEDA meeting

  3. Light-output response: why? The light-output response of a scintillator has to be addressed carefully when estimating the efficiency or the cross-talk effect In fact, the actual signal intensity from a PMT depends on the light-output. Scintillator PMT light charge Neutron electronics Neutrons with the same energy do not always produce the same light output, i.e. the same signal intensity NEDA meeting

  4. Scintillator light response • The energy of the particle(s) scattered by collisions with the incoming neutrons • The kind of the particle(s) scattered by collisions with the incoming neutrons • Other characteristics of the scintillator such as the optical coupling to the PMT, the light transport and reflection in the scintillator itself… The light-response depends on: NEDA meeting

  5. Light-output importance for NEDA Realistic estimation of the intensity of output signals Simulation for neutron detector J. Ljungvall et al., NIM A 528 (2004), 741. The final goal is to obtain a credible evaluation of some key parameters such as efficiency and cross talk NEDA as multiplicity filter to select n-rich reaction channels NEDA meeting

  6. Light-output definition The light-output L is usually given in MeVee: the particle energy required to generate 1 MeVee of light is defined as 1 MeV for fast electrons e- @ 1 MeV Light: 1MeVee PMT e- range L is generally less for heavier particles such as protons, deuterons, alphas, beryllium, carbon… Therefore, the light output L in a certain path dx is a function of the deposited energy E in dx: L(E) NEDA meeting

  7. Light-output estimation The Birks-Chou formula provides a theoretical description of the light emission However, an easier phenomenological formula is also available E - ΔE ΔL = light output of the particle scattered by a neutron in a single ith step of its stopping process E NEDA meeting

  8. Light output parametrization (1) Dekempeneer et Liskien NIM A 256 (1987) 489-498: NE213 The light-output function provided for protons is a polynomial one (3rd order ) : LP(E)=A0+A1E+A2E2+A3E3 Carbon, Boron: L(E) = 0.0097 E Deuteron: L(E) = 2 Lp(E/2) Be: L(E) = 0.013E • 0.0201E1.871 E < 6.76 MeV • -0.6278+0.1994 E E ≥ 6.76 MeV Alpha: L(E) = NEDA meeting

  9. Light output parametrization (2) Many parameterizations exist in literature, also for energies above 16 MeV. R.A. Cecil et al. NIM 161 (1979) 439-447, for example N.P. Hawks et al., NIM A 476 (2002) 190 D. Cano-Ott and collaborators, private comm. NEDA meeting

  10. Light output parametrization (3) µ = 0.045 β = 0.075 Y = 0.002 Gaussian resolution for L H. Schölermann and H. Klein, NIM 169 (1980), 25 The resolution describes: Light transmission from different points (µ)‏ Statistical effects on light production (β)‏ Noise (Y)‏ NEDA meeting

  11. Light output for 10 MeV neutrons(electrons) Light output Deposited energy 10* keV 10 * keVee 16/06/2009 NEDA meeting NEDA meeting 11

  12. Light output for 10 MeV neutrons(protons) Deposited energy Light output 10 * keV 10 * keVee NEDA meeting

  13. Light output for 10 MeV neutrons(carbon) Deposited energy Light output 10 * keV 10 * keVee NEDA meeting

  14. Light output for 10 MeV neutrons(alphas from 12C+n->9Be+4He) Light output Deposited energy 10 * keV 10 * keVee NEDA meeting

  15. Light output for 10 MeV neutrons(9Be from 12C+n->9Be+4He) Light output Deposited energy 10 * keV 10 * keVee NEDA meeting

  16. Light output for 10 MeV neutrons(deuterons) Light output Deposited energy 10 * keV 10 * keVee NEDA meeting

  17. Light output for 10 MeV neutrons(all) Light output Deposited energy 10 * keV 10 * keVee NEDA meeting

  18. Efficiency The efficiency of the NEDA prototype is calculated for an emission at 1m distance with an angular aperture of θ =14° θ Tayfun Huyuk, private comm. source 1 m The efficiency has been calculated for 4 different thresholds as: NEDA meeting

  19. Threshold (MeVee)‏ Efficiency % 0 74.6 0.25 6.5 0.50 6.0 0.75 5.5 Threshold (MeVee)‏ Efficiency % 0 63.6 0.25 40.1 0.50 36.2 0.75 33.1 Efficiency: results 1 MeV n 0.75 0.50 0.25 10 keVee 8 MeV n 0.25 0.75 0.50 10 keVee 16/06/2009 NEDA meeting NEDA meeting 19

  20. Cross talk Cross talk: the same neutron can be scattered and detected among different scintillators n' Cross talk: n Tayfun Huyuk, private comm. We calculated it for 19 detectors, in the same conditions as the efficiency simulation NEDA meeting

  21. Cross talk: results 1 MeV n 0.75 0.50 0.25 10 keVee 8 MeV n 0.25 0.75 0.50 10 keVee NEDA meeting

  22. Conclusions and open problems We have implemented in Narray code the calculations for the light output of a scintillator, considering the different kinds of recoils involved. HOWEVER… • What parameterization to be used? Several available, situation more confused for energies above 16 MeV 2. Is the light-output really a universal function? 3. Need to test the scintillator to validate simulations? NEDA meeting

  23. Light output for 10 MeV neutrons(photons) Light output Deposited energy 10 keV 10 keVee 16/06/2009 NEDA meeting NEDA meeting 23

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