An analytical model of nonproportional scintillator light yield in terms of recombination rates

Abstract

Analytical expressions for the local light yield as a function of the local deposited energy (-dE/dx) and total scintillation yield integrated over the track of an electron of initial energy E are derived from radiative and/or nonradiative rates of first through third order in density of electronic excitations. The model is formulated in terms of rate constants, some of which can be determined independently from time-resolved spectroscopy and others estimated from measured light yield efficiency as a constraint assumed to apply in each kinetic order. The rates and parameters are used in the theory to calculate scintillation yield versus primary electron energy for comparison to published experimental results on four scintillators. Influence of the track radius on the yield is also discussed. Results are found to be qualitatively consistent with the observed scintillation light yield. The theory can be applied to any scintillator if the rates of the radiative and non-radiative processes are known.2

Nonproportional scintillation response of NaI:Tl to low energy x-ray photons and electrons

“…This finding appears important because it causes the energy resolution achievable with scintillation material to be worse than what might be expected on purely statistical grounds. 5 Although the phenomenon of nonproportional response ͑nPR͒ and its relation with energy resolution ͑R͒ has been studied quite intensively [6][7][8][9][10][11][12][13][14] there are still many major gaps in our understanding of the underlying physics. Accurate data from dedicated experimental techniques are needed to reveal the true origin of nPR and energy losses inside the solid state.…”

Energy resolution and related charge carrier mobility in LaBr3:Ce scintillators

“…2,6,21,29,35,36 It is attributed to radiationless electron-hole pair recombination in the regions of a high concentration n(x) of charge carriers along the ionization track as shown in Fig. 1.…”

“…2,6,[21][22][23][24][25] This process together with an ionization density that changes along an electron track and with primary electron energy causes the deterioration of the energy resolution. To avoid the recombination losses, charge carriers should be effectively transferred from the primary track to luminescence centers.…”

Energy dependence of the relative light output of YAlO3:Ce, Y2SiO5:Ce, and YPO4:Ce scintillators

“…The nonproportionality of scintillators is consid ered to be caused by nonradiative recombination of electron-hole pairs (quenching), which exhibits a nonlinear dependence on the ionization density [16,18,[36][37][38]. Together with the variability of the local KY E ionization density along an electron track, this process causes the energy resolution of scintillation materials to deteriorate.…”

“…By the nonproportionality of the relative light output is meant the nonlinear dependence of the number of light pho tons produced in the scintillator, on the absorbed radi ation energy. Serious attempts have recently been made to reveal the mechanism of the nonproportion ality and develop the theoretical model capable of pre dicting both the nonproportionality scale and the energy resolution of scintillation materials [15][16][17][18][19][20]. However, most of the models existing today can only describe available experimental data, but are incapable of predicting the behavior of new scintillators.…”