二维位置灵敏探测器输出图像畸变的修正

高分辨(e,2e)谱仪采用二维位置灵敏探测器同时对能量和角度进行多道测量.二维位置灵敏探测器由级联使用的微通道板和电阻阳极板组成,由于电阻阳极板的边缘效应和制造工艺的缺陷,测量得到的位置图像与实际图像总会有一定的形变,存在一定的非线性.本文针对高分辨(e,2e)谱仪二维位置灵敏探测器输出图像的“桶形”畸变及位置非线性,采用一种简易的冷刻法(用脉冲信号来模拟真实电子束团),检验了二维位置灵敏探测器的Gear型电阻阳极板的线性好坏,并用分割成小三角形的方法找出测量得到的畸变图像与原始真实图像的映射关系,再用此关系对其它测量得到的畸变图像进行修正,并对修正的结果进行了评估.通过修正,由“桶形”畸变所造成的图像扭曲得到明显改善.修正后的x方向非线性由修正前的2.1%变为0.59%.这种检验和修正方法对其它领域类似探测器输出图像的修正也有一定的指导意义.

The correction of the image from two-dimensional position-sensitive detector

Two-dimensional position-sensitive detector was employed in a recently developed high-energy-resolution(e,2e) spectrometer to simultaneously measure the energies and relative azimuthal angles of the outgoing electrons in a wide range.The position-sensitive detector is composed of micro-channel plates and a Gear-type resistive anode encoder.Due to edge effect and the limitation of manufacturing techniques,the image that we measure will always have distortion from the original one.In the present paper,the non-linearity of the resistive anode encoder in the high-energy-resolution(e,2e) spectrometer was inspected in a simple way by using electric pulses instead of input charge cloud.By dividing the image into small triangles,a mapping relation was established between the distorted image and the original one.Then the spatial distortion of another measured image was corrected according to this relation and the correction results were evaluated.After the correction,the barrel distortion was obviously improved and the integral nonlinearity decreased to 0.59% from 2.1% along x-axis.This method of correction can be extended to the other similar detectors.