菲涅耳波带板X射线成像的快速计算方法

菲涅耳波带板直接成像,应用到激光等离子体或惯性约束聚变靶的X射线成像诊断,可实现μm甚至亚μm的空间分辨能力。在对成像进行数值模拟时,考虑到光源的光谱带宽和几何尺度对成像的影响,要进行菲涅耳-基尔霍夫衍射积分与卷积等数值计算,需占用大量计算机内存并且耗费运行机时。改进了数值计算方法,采用了蒙特卡罗积分法和新的卷积算法。模拟了菲涅耳波带板对大尺度多色X射线源的二维成像,新算法与以往算法相比,可显著减少运算机时,在台式机上实现模拟成像的快速计算。结果表明随着光源尺度增大、光谱带宽增加,像的背景增强,导致反衬度与成像质量下降。

Fast computing method for X-ray imaging by a Fresnel zone plate

Direct X-ray imaging using a Fresnel zone plate (FZP) in the applications of laser plasma or inertial confinement fusion diagnostics has the potential for realizing high spatial resolution in the range of micrometers to sub-micrometers. For such an FZP imaging, the influences of the object size and the spectral bandwidth of the illuminating light have to be considered. In the simulations, numerical calculations such as the Fresnel-Kirchhhoff diffraction integral and convolutions have to be done, which will take a large amount of computer memories and cost a lot of computing time. In this paper we report improved algorithms for these numerical calculations by adopting the Monte-Carlo integration and a new algorithm of convolution. By simulating the two-dimensional imaging of an extended polychromatic X-ray source, it shows that the new algorithm has significant advantages in reducing the computing time over the past algorithms, and thus such simulations can be done by a desktop computer. The imaging indicates that with the increase of the object size and/or the spectral bandwidth, the image background is enhanced which causes the decrease of the contrast and also the image quality.