大曲率弧矢弯曲复合晶体的研制

为提升国家同步辐射实验室X射线吸收精细结构(NSRL-XAFS)的光束线性能,提出将现有双平面晶单色器改造成弧矢聚焦双晶单色器的思想。采取将晶体与钛合金复合的工艺,实现了晶体的大曲率弹性弯曲,并将其用作弧矢聚焦晶体单色器中第二晶体的成像元件。鉴于NSRL-XAFS实验的光学要求,设计制作了复合晶体试验模型,通过有限元分析计算和长程面形仪实际测量得到了不同弯曲半径下晶体的面形精度,并用激光模拟其聚焦性能。结果表明,在缩放比为1/3时,样品上的成像束斑水平尺度(FWHM)由43mm(无聚焦)缩小到3mm,光子密度提高了近一个量级。这些结果满足NSRL在现有光源条件下提升XAFS数据采集质量的要求。

Development of assembly sagittal focusing crystals with large curvatures

To improve the performance of beamline for X-ray Absorption Fine Structure (XAFS) in National Synchrotron Radiation Laboratory(NSRL), an idea to reform the current double-crystal monochromator into a sagittal focusing crystal monochromator was proposed. An assembly crystal which cements the silicon strips with the tops of titanium stiffening ribs was developed to used as an imaging element of the second crystal of the sagittal focusing monochromator and to minimize the anticlastic curvature and lower the breaking risk of sagittal bent crystal. Based on the parameters of the NSRL-XAFS beamline, a model of assembly crystal was designed and its focusing properties were evaluated by finite element analysis and were measured with a long-trace-profiler. The results indicate that the Full Wave at Half Maximum(FWHM) of beam spot on the sample is decreased to 3 mm from 43 mm(without focusing) in horizon, and the photon density on the sample is increased by one order of magnitude. The results meet the requirements of data quality in current available light sources.