X-ray monochromator with an ultra-narrow band width

利用（+，+）或（+.-，- ，+）设置Si晶体的高阶非对称反射。如果我们采用这种方法达到亚meV，不对称因子增加，硅晶体的辐射面积变大。在这种情况下，在大面积上需要晶体的高完整性，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晶体面积的法布里-珀罗型X射线单色器。它是由一组两个晶体板面对面安排，其中的衍射条件与布拉格角接近π/2的满足。在两片板之间发生多次反射，干涉使透射的X射线具有超窄的带宽，作为实现Fabry-Perot型X射线单色器的第一步，研究了正入射条件下Si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样相当吻合。Fabry-Perot型X射线单色器的详细模拟显示，一组两个晶体板与200微米的厚度安排面对面与600微米的间隔，使0.67997 * X射线与0.09毫电子伏带宽的0.016反射。我们制作了这种单色器，并使用Si 999非对称反射的高分辨率单色器对其性能进行了表征。虽然没有达到预期的分辨率，但通过对切割工艺的改进和所用测角仪的超精细旋转，有可能实现这种新型的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.