Research On Characteristics Of The Photodiode Detector In Industrial Computed Tomography

ICT is the abbreviation of Industrial Computed Tomography, which is composed of radiation source system, detection system, mechanism and automatic control system, data acquisition system and computer image process system. Detection system is the key subsystems whose property has a direct influence on the image quality and performance of the entire Industrial CT system. It is of great importance to improve the performance of detector for industrial CT system research and development, and great value on engineering applications and academic by researching the characteristics of Industrial CT detector.In order to design the detector and select devices targetedly, and to improve the detector performance effectively, several factors were researched, which have impact on sensitivity, linear range, and stability of the detector. After comparing the advantages and disadvantages, and the application scope of several common radiation detectors, the structure and principle of a most widely used scintillation photodiode detector in ICT system was emphatically analyzed. Then characteristics of scintillation and photodiode were further studied. It mainly described the characteristics such as luminous efficiency, emission spectra, and decay time of common scintillator. In order to find out some measures to improve the efficiency of light collection, a simulation study for light collection efficiency of scintillation crystal was carried out by means of Monte Carlo method. In order to study on the characteristics of photodiode, a system was designed, consisting of low noise amplifier circuit and optical path for photodiode. Experiments of photodiode characteristics were carried out on this system.On the basis of studying on the characteristics of scintillator and photodiode, three measures to improve the performance of detector were put forward.①Defining The Match Degree between scintillator and photodiode, providing a theoretical basis for selection.②Photodiodes should be tested after purchasing to ensure their properties.③A temperature control system was to be designed to hold the detector's temperature and improve the performances if it's necessary.Finally, sensitivity of scintillation photodiode detector was studied and a mathematical expression with general significance was obtained. The research of sensitivity offers the ethical basis for estimating the dose of X-ray source, the dynamic range of detection and other parameters. It has most guiding significance for the selecting of X-ray source, the designing of detector and the calculating the distance between X-ray source and detections.