Potential use of V-channel Ge(220) monochromators in X-ray metrology and imaging.
Potential use of V-channel Ge(220) monochromators in X-ray metrology and imaging.
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DOI：
10.1107/s0021889813006122
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发表时间：
2013-08-01
影响因子：
6.1
通讯作者：
Jergel M
中科院分区：
文献类型：
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作者：
Korytár D;Vagovič P;Végsö K;Siffalovič P;Dobročka E;Jark W;Ač V;Zápražný Z;Ferrari C;Cecilia A;Hamann E;Mikulík P;Baumbach T;Fiederle M;Jergel M
分析了用于计量和成像应用的 V 通道 X 射线单色仪中调节更高不对称系数 (>10) 的几种方法。对于成分和热调节的情况，强度增加了六倍以上。虽然通道切割晶体（其中非对称切割中的衍射表面保持平行）可以提供光束准直和光谱光束整形，但如果切割是 V 形，它们还可以提供光束压缩或扩展。在这种情况下，压缩/膨胀比取决于总不对称系数。如果使用Ge(220)衍射平面和超过10的总不对称因子，则仅当第二个衍射器相对于第一个衍射器稍微调谐时，两个衍射器的摇摆曲线才会有足够的重叠。这项研究比较并分析了当 Cu Kα1 光束在 V21 单色仪中压缩 21 倍时克服这种由折射引起的不匹配的几种方法。如果通过成分变化或热变形来改善匹配，则可以获得六倍以上的强度增加。与在对称通道切割单色仪中使用简单狭缝相比，这提供了强度增益。还描述了通过引入不同类型的 X 射线棱镜来满足所需的光束偏转来克服失配的第一次尝试。 V 形单色仪的性能在两个应用中得到了证明。在光束压缩模式下获得的窄准直单色光束用于对表面损坏的硅样品进行高分辨率掠入射小角度 X 射线散射测量。此外，基于扩束模式下的两个交叉V15通道单色仪并通过不等不对称性调谐的二维布拉格放大器与Medipix探测器结合成功应用于测试结构的高分辨率成像。
Several ways of tuning a higher asymmetry factor (>10) in V-channel X-ray monochromators, for metrological and imaging applications, were analysed. A more than sixfold intensity increase for compositionally and thermally tuned cases was achieved. While channel-cut crystals, in which the diffracting surfaces in an asymmetric cut are kept parallel, can provide beam collimation and spectral beam shaping, they can in addition provide beam compression or expansion if the cut is V-shaped. The compression/expansion ratio depends in this case on the total asymmetry factor. If the Ge(220) diffraction planes and a total asymmetry factor in excess of 10 are used, the rocking curves of two diffractors will have a sufficient overlap only if the second diffractor is tuned slightly with respect to the first one. This study compares and analyses several ways of overcoming this mismatch, which is due to refraction, when the Cu Kα1 beam is compressed 21-fold in a V21 monochromator. A more than sixfold intensity increase was obtained if the matching was improved either by a compositional variation or by a thermal deformation. This provided an intensity gain compared with the use of a simple slit in a symmetrical channel-cut monochromator. The first attempt to overcome the mismatch by introducing different types of X-ray prisms for the required beam deflection is described as well. The performance of the V-shaped monochromators is demonstrated in two applications. A narrow collimated monochromatic beam obtained in the beam compressing mode was used for high-resolution grazing-incidence small-angle X-ray scattering measurements of a silicon sample with corrupted surface. In addition, a two-dimensional Bragg magnifier, based on two crossed V15 channel monochromators in beam expansion mode and tuned by means of unequal asymmetries, was successfully applied to high-resolution imaging of test structures in combination with a Medipix detector.