Scintillation response of CsI(Tl) and CsI(Na) crystals on excitation by X-rays and low energy gamma-rays

Abstract

The dependence on the response (L/E) on energy (E) in the range of 5.9...60 keV has been investigated for CsI(Na) during the aging and for CsI(Tl) crystals with different activator concentrations and light collection conditions. On the contrast to data on increasing of L/E in the range of ~15keV (so called the response non-proportionality up to +24%), we have shown that value and sign of non-proportionality are determined by light collection conditions, mainly and scintillation material (luminescence centers concentration) in the minor. The distinct correlation is observed between non-proportionality and energy resolution in the low energy range even where is supposed the non-proportionality contribution is insignificant. The main conclusion is the response non-proportionality is not fundamental property of the scintillator. It (and energy resolution) rise from light collection conditions for the quantum with different penetration depth and scintillation long.