A Study on Non-proportionality of Phoswich Detector Using Monte Carlo Simulation

몬테칼로 전산모사를 이용한 Phoswich 계측기의 비선형성 연구

  • Published : 2004.12.30

Abstract

Using the Monte Carlo simulation, a study on the lion-proportionality of the prototype phoswich detector with $2'{\times}2'$ CSI(Tl) and plastic scintillator, which was made by KAERI, has been carried. The defector response functions (DRFs) calculated by simulations were compared with the experimental measurement on the $^{137}Cs\;and\;^{60}Co$. To precisely simulate the DRF for the phoswich, the CSI(Tl) non-proportionality was calculated using the electron response and the simplified electron cascade sequence for treating the photoelectric absorption event. The resulting DRFs of $^{137}Cs\;and\;^{60}Co$ sources obtained by simulations were compared with experiments for verification. For $^{137}Cs$, gamma-ray responses simulated by MCNP5 are generally good agreement with the measured ones. But the DRF of $^{60}Co$ does not match well with the results of experiment in the energy region below second peak due to the coincidence effect of two gamma-rays (1.17 MeV and 1.33 MeV). Through the analysis of the non-proportionality of CsI(Tl) in the prototype phoswich, the improved DRFs considering non-proportionality were produced and the simulation results were verified using the experimental measurements. However, to more precisely reproduce the DRF for the phoswich, further studies in relation to the electron channeling effect and the Doppler broadening effect of a scintillator are still needed as well as considering that effect of the transfer contribution.

References

  1. Rooney, B.D. and Valentine, J.D., 'Scintillator light yield nonproportionality: calculating photon response using measured electron response', IEEE transactions on nuclear science, v.44 no.3 pt.l, pp.509-516(1997)
  2. Mengesha, W., Taulbee, T.D., Rooney, B.D., and Valentine, J.D., 'Light Yield Nonproportionality of CsI(T1), CsI(Na), and YAP', IEEE transactions on nuclear science, v.45 no.3 pt.I, pp.456-461(1998)
  3. Moszynski, M, 'Inorganic Scintillation Detectors in gamma-ray spectrometry', Nuclear instruments & methods in physics research Section A, Accelerators, spectrometers, detectors and associated equipment, v.505 no.1/2, pp.101-110 (2003)
  4. Gardner, R.P. and Sood, A.A, 'Monte Carlo simulation approach for generating Nal detector response functions (DRFs) that accounts for non linearity and variable flat continua', Nuclear instruments & methods in physics research Section B, Beam interactions with materials and atoms, v.213, pp.87-99(2004)