Zhang Fan, Allen Andrew J, Levine Lyle E, Long Gabrielle G, Kuzmenko Ivan, Ilavsky Jan
Material Measurement Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MA 20899, USA.
X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA.
J Synchrotron Radiat. 2018 Sep 1;25(Pt 5):1354-1361. doi: 10.1107/S1600577518009645. Epub 2018 Aug 14.
This work reports a harmonic-rejection scheme based on the combination of Si(111) monochromator and Si(220) harmonic-rejection crystal optics. This approach is of importance to a wide range of X-ray applications in all three major branches of modern X-ray science (scattering, spectroscopy, imaging) based at major facilities, and especially relevant to the capabilities offered by the new diffraction-limited storage rings. It was demonstrated both theoretically and experimentally that, when used with a synchrotron undulator source over a broad range of X-ray energies of interest, the harmonic-rejection crystals transmit the incident harmonic X-rays on the order of 10. Considering the flux ratio of fundamental and harmonic X-rays in the incident beam, this scheme achieves a total flux ratio of harmonic radiation to fundamental radiation on the order of 10. The spatial coherence of the undulator beam is preserved in the transmitted fundamental radiation while the harmonic radiation is suppressed, making this scheme suitable not only for current third-generation synchrotron sources but also for the new diffraction-limited storage rings where coherence preservation is an even higher priority. Compared with conventional harmonic-rejection mirrors, where coherence is poorly preserved and harmonic rejection is less effective, this scheme has the added advantage of lower cost and footprint. This approach has been successfully utilized at the ultra-small-angle X-ray scattering instrument at the Advanced Photon Source for scattering, imaging and coherent X-ray photon correlation spectroscopy experiments. With minor modification, the harmonic rejection can be improved by a further five orders of magnitude, enabling even more performance capabilities.
这项工作报道了一种基于硅（111）单色仪和硅（220）谐波抑制晶体光学元件相结合的谐波抑制方案。这种方法对于基于大型设施的现代X射线科学的所有三个主要分支（散射、光谱学、成像）中的广泛X射线应用都很重要，尤其与新的衍射极限储存环所提供的能力相关。理论和实验均表明，当与同步加速器波荡器源配合使用于广泛的感兴趣的X射线能量范围内时，谐波抑制晶体传输的入射谐波X射线量级为10。考虑到入射光束中基波和谐波X射线的通量比，该方案实现的谐波辐射与基波辐射的总通量比量级为10。在抑制谐波辐射的同时，传输的基波辐射中保留了波荡器光束的空间相干性，这使得该方案不仅适用于当前的第三代同步加速器源，也适用于对相干性保持要求更高的新的衍射极限储存环。与传统的谐波抑制镜相比，传统谐波抑制镜的相干性保留较差且谐波抑制效果较差，该方案还具有成本更低和占地面积更小的额外优势。这种方法已在先进光子源的超小角X射线散射仪器上成功用于散射、成像和相干X射线光子相关光谱实验。通过进行微小修改，谐波抑制可进一步提高五个数量级，从而实现更多的性能。
