Luminescence principle and characteristics of imaging plate

Abstract

The imaging plate (IP) is a reusable detector for detecting radiation particles in a complex electromagnetic field environment, and it is widely used as a detection medium in laser-accelerated particle beam diagnostic equipment. Therefore, it is necessary to study the performance characteristics and physical mechanism of IP. An electron source with known activity is used to explore the performance characteristics of IP. A ⁹⁰Sr/⁹⁰Y electron source is used to measure the time attenuation curve, calibrate the absolute sensitivity, and study the law of multiple scanning of BAS-SR and BAS-TR. In the case of a longer irradiation, the fading cannot be neglected, and the attenuation curves are modified. The time attenuation characteristics indicate that the IP should be cooled after irradiation, and the scanning should be carried out in the slow decay process to reduce the influence of the reading error in the decay process. The absolute sensitivity of BAS-SR and BAS-TR to ⁹⁰Sr/⁹⁰Y source are (0.033±0.002) PSL/<i>e</i> and (0.018±0.0038) PSL/<i>e</i> (photostimulated light, PSL), respectively, which are consistent with the results of most absolute sensitivity. The absolute sensitivity is closely related to the type of IP, scanning equipment, and experimental environment. In addition, the energy spectrum integral effect of the broad spectrum <i>β</i> source has a significant influence on the absolute sensitivity. This method is only suitable for the rough evaluation of the sensitivity characteristic parameters of the IP. Multiple scanning approximately satisfies the double exponential function distribution, which is consistent with the physical model. The characteristics of IP are determined by its storage principle. The fluorescence layer of IP is composed of typical electron trapping materials <i>M</i>F<i>X</i> (<i>M</i> = Ca, Sr, Ba; <i>X</i> = C1, Br, I) alkaline earth metal fluorhalide BaFBr. When the IP is irradiated, a large number of free electron-hole pairs are excited by the deposited energy in the material, and the free electrons will be captured by the electron trap, so the fluorescence layer of the IP records the radiation particles’ information through the energy deposited. In this paper, we study three kinds of models. Based on the models, a photo-stimulated luminescence model is proposed to describe the electron transfer process. The photo-stimulated luminescence model describes the physical mechanism of energy deposition, information storage, and information scanning of radiation particles. The relationship between the physical mechanism and characteristics is explained effectively by combining the microscopic mathematical model with the macroscopic physical phenomenon. It provides a specific data basis for the subsequent application of IPs in laser plasma diagnostic experiments.