Calculating the Ratio of Radiation Rays Falling on Detector Chip from Inner Wall of Cold Shield with Monte Carlo Method and MATLAB
用蒙特卡罗方法和MATLAB计算冷屏内壁表面辐射光线落入探测器芯片的比例

A method for calculating the ratio of the radiation rays falling on a detector chip from the inner wall of a circular cold shield by using the Monte Carlo method and MATLAB is presented. It is based on the directional number concept in three-dimensional space. First, a random point on the surface of the inner wall in the cold shield is generated with MATLAB. Then, a group of random directional numbers is associated to that point to form an equation for a random straight line and wether it is projected to the chip plane directly or to the chip plane after reflection is judged. In the case of reflection, the radiation rays reflected from the inner wall of the cold shield are generated according to the property of specular reflection and wether they fall on the chip region is judged. After statistical analysis, the ratio of the number of the radiation rays falling on the detector chip to the total number of the radiation rays emitted from the surface of the inner wall of the cold shield can be calculated. This method has the features of easy programming and simple operation.