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Title: Experimental and computational results on exciton/free-carrier ratio, hot/thermalized carrier diffusion, and linear/nonlinear rate constants affecting scintillator proportionality

Abstract

Models of nonproportional response in scintillators have highlighted the importance of parameters such as branching ratios, carrier thermalization times, diffusion, kinetic order of quenching, associated rate constants, and radius of the electron track. For example, the fraction ηeh of excitations that are free carriers versus excitons was shown by Payne and coworkers to have strong correlation with the shape of electron energy response curves from Compton-coincidence studies. Rate constants for nonlinear quenching are implicit in almost all models of nonproportionality, and some assumption about track radius must invariably be made if one is to relate linear energy deposition dE/dx to volume-based excitation density n (eh/cm3) in terms of which the rates are defined. Diffusion, affecting time-dependent track radius and thus density of excitations, has been implicated as an important factor in nonlinear light yield. Several groups have recently highlighted diffusion of hot electrons in addition to thermalized carriers and excitons in scintillators. However, experimental determination of many of these parameters in the insulating crystals used as scintillators has seemed difficult. Subpicosecond laser techniques including interband z scan light yield, fluence-dependent decay time, and transient optical absorption are now yielding experimental values for some of the missing rates and ratios neededmore » for modeling scintillator response. First principles calculations and Monte Carlo simulations can fill in additional parameters still unavailable from experiment. As a result, quantitative modeling of scintillator electron energy response from independently determined material parameters is becoming possible on an increasingly firmer data base. This paper describes recent laser experiments, calculations, and numerical modeling of scintillator response.« less

Authors:
; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1130729
Report Number(s):
PNNL-SA-99335
NN2001000
DOE Contract Number:
AC05-76RL01830
Resource Type:
Conference
Resource Relation:
Conference: Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XV, August 25, 2013, San Diego, California. Proceedings of the SPIE, 8852:Paper No. 88520J
Country of Publication:
United States
Language:
English

Citation Formats

Williams, Richard, Grim, Joel, Li, Qi, Ucer, K. B., Bizarri, G. A., Kerisit, Sebastien N., Gao, Fei, Bhattacharya, Pijush, Tupitsyn, Eugene, Rowe, Emmanuel, Buliga, Vladimir M., and Burger, Arnold. Experimental and computational results on exciton/free-carrier ratio, hot/thermalized carrier diffusion, and linear/nonlinear rate constants affecting scintillator proportionality. United States: N. p., 2013. Web. doi:10.1117/12.2027716.
Williams, Richard, Grim, Joel, Li, Qi, Ucer, K. B., Bizarri, G. A., Kerisit, Sebastien N., Gao, Fei, Bhattacharya, Pijush, Tupitsyn, Eugene, Rowe, Emmanuel, Buliga, Vladimir M., & Burger, Arnold. Experimental and computational results on exciton/free-carrier ratio, hot/thermalized carrier diffusion, and linear/nonlinear rate constants affecting scintillator proportionality. United States. doi:10.1117/12.2027716.
Williams, Richard, Grim, Joel, Li, Qi, Ucer, K. B., Bizarri, G. A., Kerisit, Sebastien N., Gao, Fei, Bhattacharya, Pijush, Tupitsyn, Eugene, Rowe, Emmanuel, Buliga, Vladimir M., and Burger, Arnold. Tue . "Experimental and computational results on exciton/free-carrier ratio, hot/thermalized carrier diffusion, and linear/nonlinear rate constants affecting scintillator proportionality". United States. doi:10.1117/12.2027716.
@article{osti_1130729,
title = {Experimental and computational results on exciton/free-carrier ratio, hot/thermalized carrier diffusion, and linear/nonlinear rate constants affecting scintillator proportionality},
author = {Williams, Richard and Grim, Joel and Li, Qi and Ucer, K. B. and Bizarri, G. A. and Kerisit, Sebastien N. and Gao, Fei and Bhattacharya, Pijush and Tupitsyn, Eugene and Rowe, Emmanuel and Buliga, Vladimir M. and Burger, Arnold},
abstractNote = {Models of nonproportional response in scintillators have highlighted the importance of parameters such as branching ratios, carrier thermalization times, diffusion, kinetic order of quenching, associated rate constants, and radius of the electron track. For example, the fraction ηeh of excitations that are free carriers versus excitons was shown by Payne and coworkers to have strong correlation with the shape of electron energy response curves from Compton-coincidence studies. Rate constants for nonlinear quenching are implicit in almost all models of nonproportionality, and some assumption about track radius must invariably be made if one is to relate linear energy deposition dE/dx to volume-based excitation density n (eh/cm3) in terms of which the rates are defined. Diffusion, affecting time-dependent track radius and thus density of excitations, has been implicated as an important factor in nonlinear light yield. Several groups have recently highlighted diffusion of hot electrons in addition to thermalized carriers and excitons in scintillators. However, experimental determination of many of these parameters in the insulating crystals used as scintillators has seemed difficult. Subpicosecond laser techniques including interband z scan light yield, fluence-dependent decay time, and transient optical absorption are now yielding experimental values for some of the missing rates and ratios needed for modeling scintillator response. First principles calculations and Monte Carlo simulations can fill in additional parameters still unavailable from experiment. As a result, quantitative modeling of scintillator electron energy response from independently determined material parameters is becoming possible on an increasingly firmer data base. This paper describes recent laser experiments, calculations, and numerical modeling of scintillator response.},
doi = {10.1117/12.2027716},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Oct 01 00:00:00 EDT 2013},
month = {Tue Oct 01 00:00:00 EDT 2013}
}

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