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基于一台COMET公司MXR-225/22型号,最大出射X射线能量为225keV的X射线机,在此基础上要尽可能得到高的探测效率和输出光子产额。通过GEANT4[1]工具包建立模型,模拟得到了改变CsI(Tl)晶体的厚度、X射线能量以及入射角的情况下,其探测效率、输出率以及输出光子产额的变化;同时,通过实验测得光电二极管暗电流曲线,并且根据模拟结果,结合光电二极管的特性参数,计算了在管电压为225kV,不同管电流、不同距离的情况下,探测器输出电流的大小,并与实验测得的数据进行对比。
Based on a COMET MXR-225/22 model, an X-ray machine capable of emitting a maximum of 225 keV of X-ray energy is used. On the basis of this, high detection efficiency and output photon yield are obtained as much as possible. The model of GEANT4 [1] was built to simulate the changes of detection efficiency, output rate and output photon yield when the thickness of CsI (Tl) crystal, X-ray energy and incident angle were changed. At the same time, The dark current curve of the photodiode was measured. According to the simulation results and the characteristic parameters of the photodiode, the output current of the detector was calculated under the condition of the tube voltage of 225 kV, different tube currents and different distances, Data comparison.