Luminescence response of CsI:Na to electron pulse irradiation

Abstract

This paper investigates the influence of activator concentration and temperature on the scintillation process in CsI:Na crystal which was excited by a pulsed electron beam (Eex ¼ 0.25 MeV, t1/2 ¼ 15 ns, W ¼ 0.003.0.16 J/cm2 ) at temperature within 77e300 K. It has been established that the transition of Na-bound two halide exciton from singlet state causes 3 eV emission of CsI:Na. The capturing of Vk by Naþ ion determines the scintillation pulse shape. Thermal liberation of Vk from VkA centers results in an inertial rise of the emission pulse in lightly activated CsI:Na and in a mono-exponential decay of the emission pulse in heavily activated CsI:Na. The value of thermal dissociation energy of VkA centers is 0.24 0.01 eV, which was obtained from the temperature dependences of the emission decay time constant for CsI:2.8∙10 3%Na and of the rise time constant for CsI:2.0∙10 4%Na.