X-ray monochromator with an ultra-narrow band width

通过对硅晶体的高阶不对称反射进行(，)或(.-，-，)设置，可以获得几个MeV-1 meV带宽的单色化X射线。如果将这种方法应用到亚MEV，则非对称因子增加，硅晶体的辐射面积变大。在这种情况下，对大面积的晶体要求很高，我们现在很难得到这样的FZ-Si晶体。因此，我们试图研制一种只需要很小面积的晶体的法布里-珀罗型X射线单色仪。它由一组面对面排列的两片晶片组成，其中满足布拉格角接近pi/2的衍射条件。两个平板之间发生多次反射，这种干涉使X射线的透射率具有超窄的带宽。作为实现法布里-珀罗型X射线单色仪的第一步，研究了垂直入射条件下硅晶体的反射率和透射率。它与根据达尔文方法计算的衍射图相当吻合。对法布里-珀罗型X射线单色仪的详细模拟表明，两块厚度为200um的晶片以600um的间隔面对面排列，通过0016的反射获得了带宽为0.09meV的0.67997×X射线。我们制作了这种单色仪，并用Si999不对称反射的高分辨率单色仪对其性能进行了表征。虽然没有达到预定的分辨率，但通过改进切割工艺和使用超精密旋转测角仪，可以实现这种新型的X射线单色仪。

Monochromatized X-ray with several meV-1meV band width can be obtained by the (+, +) or (+.-, -, +) setting of the higher order asymmetric reflection of the Si crystal. If we apply this method to reach to sub meV,the asymmetric factor increases and the radiated area of the Si crystal becomes large. In this case high perfection of the crystal is needed in the large area and we are now hard to get such a FZ Si crystal. So we have tried to develop the Fabry-Perot type X-ray monochromator which needs only a small area of the crystal. It is composed of a set of two crystal plates arranged face to face in which the diffraction condition with a Bragg angle near pi/2 is satisfied. Multiple reflection is occurred between two plates and the interference makes the transmitted X-ray with an ultra-narrow band width.The reflectivity and transitivity of Si crystal at the normal incidence condition was investigated as the first step to realize the Fabry-Perot type X-ray monochromator. It agreed fairly well with the diffraction pattern calculated on the basis of the Darwin approach. The detailed simulation of the Fabry-Perot type X-ray monochromator revealed that a set of two crystal plates with a 200 mum thickness arranged face to face with a 600 mum interval makes 0.67997 * X-ray with 0.09 meV band width by the 0 0 16 reflection. We made this monochromator and characterized its performance using the high resolution monochromator with Si 999 asymmetric reflection. The aimed resolution is not achieved, but the improvement of the process of the cutting and the used goniometer with an ultra-fine rotation may realize this novel X-ray monochromator.