激光高能X射线成像中探测器表征与电子影响研究

基于激光尾场加速电子的高能X射线源具有高光子能量与小源尺寸的特点,在高空间分辨无损检测方面发挥着十分重要的作用.在X光机上测量了CsI针状闪烁屏、锗酸铋(BGO)闪烁阵列与DRZ闪烁屏的本征空间分辨率,并模拟了三类探测器对高能X射线的能量沉积响应,其中CsI针状闪烁屏的空间分辨率高达8.7 lp/mm.采用Ta转换靶产生的高能X射线开展透视照相,能够分辨最高面密度33.0 g/cm~2的两层客体结构.开展了X射线照相、X射线与电子混合照相以及电子照相三种情况的比对实验,在X射线产额不足或探测效率不够情况下采用X射线与电子混合透视照相的方案,以牺牲对比度为代价,能较大程度地提高图像信号强度.

Detector characterization and electron effect for laser-driven high energy X-ray imaging

High energy X-ray sources based on laser-wakefield accelerated electron beams have several important advantages, including high photon energy and small source size, and have many important applications such as high resolution radiography in non-destructive testing. Firstly, the thickness of electron converter is optimized with the targets Ta, W and Pb each with an optimal thickness of 2 mm. We calibrate the intrinsic spatial resolution of CsI needle-like scintillation screen, bismuth germanium oxide (BGO) scintillation array and DRZ scintillation screen with an X-ray tube. And the spatial resolution of CsI needle-like scintillation screen is as high as 8.7 lp/mm. The energy deposition responses of these three detectors to high X-ray are also simulated. Experiments show that the features of a two-layer object can be resolved up to an area density of 33.0 g/cm² by using the high X-ray source generated by injecting laser-wakefield accelerated electron beam into a Ta convertor target. Experiment that compares X-ray radiography, mixed radiography of X-ray and electron, and electron radiography, is also carried out. Since low X-ray yield and low detection efficiency are two serious problems in high energy X-ray radiography based on laser-wakefield accelerated electron beams, we propose and prove a method of improving image signal intensity greatly at the cost of image contrast by adopting the mixed radiography of X-ray and electron.