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Title: Monte Carlo simulation of electron thermalization in scintillator materials: Implications for scintillator nonproportionality

Abstract

The lack of reliable quantitative estimates of the length and time scales associated with hot electron thermalization after a gamma-ray induced energy cascade obscures the interplay of various microscopic processes controlling scintillator performance and hampers the search for improved detector materials. We apply a detailed microscopic kinetic Monte Carlo model of the creation and subsequent thermalization of hot electrons produced by gamma irradiation of six important scintillating crystals to determine the spatial extent of the cloud of excitations produced by gamma rays and the time required for the cloud to thermalize with the host lattice. The main ingredients of the model are ensembles of microscopic track structures produced upon gamma excitation (including the energy distribution of the excited carriers), numerical estimates of electron-phonon scattering rates, and a calculated particle dispersion to relate the speed and energy of excited carriers. All these ingredients are based on first-principles density functional theory calculations of the electronic and phonon band structures of the materials. Details of the Monte Carlo model are presented along with results for thermalization time and distance distributions. These results are discussed in light of previous work. It is found that among the studied materials, calculated thermalization distances are positively correlatedmore » with measured nonproportionality. In the important class of halide scintillators, the particle dispersion is found to be more influential than the largest phonon energy in determining the thermalization distance.« less

Authors:
ORCiD logo [1]; ORCiD logo [2];  [3];  [4];  [1]
  1. Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, USA
  2. Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, USA
  3. National Security Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, USA
  4. Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, Michigan 48109, USA
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1426365
Report Number(s):
PNNL-SA-128275
Journal ID: ISSN 0021-8979; DN2001000
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 122; Journal Issue: 23
Country of Publication:
United States
Language:
English
Subject:
Phonons; radiation detection; scintillators; themalization; electron phonon interaction

Citation Formats

Prange, Micah P., Xie, YuLong, Campbell, Luke W., Gao, Fei, and Kerisit, Sebastien. Monte Carlo simulation of electron thermalization in scintillator materials: Implications for scintillator nonproportionality. United States: N. p., 2017. Web. doi:10.1063/1.4998966.
Prange, Micah P., Xie, YuLong, Campbell, Luke W., Gao, Fei, & Kerisit, Sebastien. Monte Carlo simulation of electron thermalization in scintillator materials: Implications for scintillator nonproportionality. United States. doi:10.1063/1.4998966.
Prange, Micah P., Xie, YuLong, Campbell, Luke W., Gao, Fei, and Kerisit, Sebastien. Thu . "Monte Carlo simulation of electron thermalization in scintillator materials: Implications for scintillator nonproportionality". United States. doi:10.1063/1.4998966.
@article{osti_1426365,
title = {Monte Carlo simulation of electron thermalization in scintillator materials: Implications for scintillator nonproportionality},
author = {Prange, Micah P. and Xie, YuLong and Campbell, Luke W. and Gao, Fei and Kerisit, Sebastien},
abstractNote = {The lack of reliable quantitative estimates of the length and time scales associated with hot electron thermalization after a gamma-ray induced energy cascade obscures the interplay of various microscopic processes controlling scintillator performance and hampers the search for improved detector materials. We apply a detailed microscopic kinetic Monte Carlo model of the creation and subsequent thermalization of hot electrons produced by gamma irradiation of six important scintillating crystals to determine the spatial extent of the cloud of excitations produced by gamma rays and the time required for the cloud to thermalize with the host lattice. The main ingredients of the model are ensembles of microscopic track structures produced upon gamma excitation (including the energy distribution of the excited carriers), numerical estimates of electron-phonon scattering rates, and a calculated particle dispersion to relate the speed and energy of excited carriers. All these ingredients are based on first-principles density functional theory calculations of the electronic and phonon band structures of the materials. Details of the Monte Carlo model are presented along with results for thermalization time and distance distributions. These results are discussed in light of previous work. It is found that among the studied materials, calculated thermalization distances are positively correlated with measured nonproportionality. In the important class of halide scintillators, the particle dispersion is found to be more influential than the largest phonon energy in determining the thermalization distance.},
doi = {10.1063/1.4998966},
journal = {Journal of Applied Physics},
number = 23,
volume = 122,
place = {United States},
year = {Thu Dec 21 00:00:00 EST 2017},
month = {Thu Dec 21 00:00:00 EST 2017}
}