低能X射线显微成像靶材的优化设计

Optimization and design of target of low energy X-ray microscopy

基于扫描电子显微镜(SEM)的X射线显微成像是利用SEM的微聚焦电子束轰击金属靶材产生的低能X射线对样品进行投影成像,可为低原子序数材料提供的一种无损检测手段.其中,靶材是影响着X射线成像质量的一个重要因素.本文利用蒙特卡罗方法模拟计算了靶材的材料和靶材与电子束作用面的倾角与探测器接收到的X射线强度的关系,仿真结果表明靶材作用面在与水平面倾角为60°时有最佳的X射线出射率;此外,在该倾角下的靶材产生的X射线强度分布均匀;实验结果也验证了这些结论.最后,使用不同材质的靶材对杨树叶样品进行成像实验,结果表明钨靶材具有较好的亮度和对比度,更适合X射线显微成像.

X-ray microscopy method based on scanning electron microscopy( SEM) is to project images for sample with the lowenergy X-ray produced from SEM’s micro-focusing electron beam bombarding metal target.This method offers a nondestructive testing method for materials with low atomic number. Metal target is an important factor influencing the quality of the X-ray image. In this article,Monte-Carlo method is used to investigate the influence of the target material and the angle( α) between the interaction face of target and horizontal plane on the dosage of the X-rayreceived by the detector. The simulation results show thatthe best performance can be reached ifangle( α) is 60°,also,the X-ray generated at this angle is uniformly distributed. The simulations are further verified by the experimental results. Finally,different target materials were used to create the images of poplar leaf samples. The tests show that the tungsten target has better brightness and contrast than the others,therefore,it is more suitable for X-ray microscopy.