振幅矢量叠加法分析X射线波带片加工误差对效率的影响

使用振幅矢量叠加法,通过叠加X射线波带片每一对环带对焦点的贡献,计算和分析了随机环带位置误差、宽度误差、扩散和粗糙度对波带片的效率的影响。用Strehl 比来量化和衡量与理想波带片有偏差的波带片的性能,对两个波带片实例分别用Strehl 极限确定了能容许的4种误差的最大值。计算了Ni软X射线波带片的随机环带位置误差及宽度误差对主焦点效率的影响;计算了SiO₂/Ni硬X射线溅射切片波带片的两种材料的相互扩散和粗糙度对衍射效率的影响。结果表明:4种误差越大,主焦点效率越小,对Ni软X射线波带片,随机环带位置误差均方根和宽度误差均方根小于最外环宽度的20%左右时,对SiO₂/Ni硬X射线溅射切片波带片,扩散区宽度和粗糙度均方根分别小于最外环宽度的90%和60%左右时,得到的Strehl 比在Strehl 极限之上。

Analysis of the influence of fabrication errors on the efficiency of X-ray zone plates by summing up the wavelets

The influence of random zone position error,width error,interdiffusion and roughness on the efficiency of X-ray zone plates(ZP) was analyzed by summing up the wavelets of every pair of rings.Strehl ratio was used to quantify and evaluate the performance of the zone plates deviating from perfect ones.The tolerances of the 4 errors mentioned above were gained by using Strehl limit in two examples.The influence of random zone position and width error on the efficiencies of a Ni soft X-ray zone plate was calculated,and the influence of interdiffusion and roughness on the efficiencies of a SiO_2/Ni hard X-ray sputtered sliced zone plate was analyzed.It is showed that the efficiency of the main focus decrease with increasing the four errors.The root-mean-square of random zone position and width error of the first zone plate need to be less than about 20% of the outmost zone width to generate a Strehl ratio higher than Strehl limit;the width of random interdiffusion region and the root-mean-square roughness of the second zone plate need to be less than about 90% and 60% of the outmost zone width to generate a Strehl ratio higher than Strehl limit respectively.