Light Collection in the High Energy X-ray Detector with the Pixelated CdWO4 Scintillator using Monte Carlo Method

Abstract

The image detector in the systems, which use the high energy x-ray as the IGRT (Image-Guided Radiation Therapy) and the container cargo inspection, is divided into two type, one of which use the direct conversion method, and the other of which use indirect conversion method[1-4]. The performance of indirect detectors, which use the scintillator as CdWO4, BGO, CsI, NaI, etc., are effected by optical properties of scintillator and geometrical condition of scintillator [4,5]. Some of generated lights by interaction between x-ray photons and scintillator are collected at the photo-sensor and others are absorbed in scintillator or escape out of detector. In order to make the high performance image detector, detector should be able to gather the generated lights as much as possible. To minimize the loss of generated lights, thickness of scintillator is to be chosen appropriately. Therefore, the quality of the image detector using the pixelated scintillator is determined by scintillator size, reflectance of scintillator surface, electric noise, etc. The CdWO4 is suitable for use as the x-ray converter due to high density, high light yield, suitable refractive index, low afterglow, etc. [5]. So, it is mainly has been used in the detector for the high energy x-ray imaging. In this paper, we calculated the change of acquisition signals according to the change of CdWO4 scintillator thickness using Monte Carlo method.ich use indirect conversion method[1-4]. The performance of indirect detectors, which use the scintillator as CdWO4, BGO, CsI, NaI, etc., are effected by optical properties of scintillator and geometrical condition of scintillator [4,5]. Some of generated lights by interaction between x-ray photons and scintillator are collected at the photo-sensor and others are absorbed in scintillator or escape out of detector. In order to make the high performance image detector, detector should be able to gather the generated lights as much as possible. To minimize the loss of generated lights, thickness of scintillator is to be chosen appropriately. Therefore, the quality of the image detector using the pixelated scintillator is determined by scintillator size, reflectance of scintillator surface, electric noise, etc. The CdWO4 is suitable for use as the x-ray converter due to high density, high light yield, suitable refractive index, low afterglow, etc. [5]. So, it is mainly has been used in the detector for the high energy x-ray imaging. In this paper, we calculated the change of acquisition signals according to the change of CdWO4 scintillator thickness using Monte Carlo method.