Topography of bent crystals with microradian resolution in one dimension

• Published in: Review of scientific instruments 2022-11, Vol.93 (11), p.113538-113538
• Main Authors: Pereira, N. R., Macrander, A. T., Harding, E. C.
• Format: Article
• Language: English
• Subjects: Analyzers; Crystal defects; Knife-edge; Quartz; Substrates; Topography; X ray imagery; X ray reflection; X-rays
• ISSN: 0034-6748; 1089-7623
• DOI: 10.1063/5.0098994

Optimum performance in x-ray imaging and spectroscopy of plasmas with bent crystals is achievable only when the crystal reflects the x rays theoretically perfectly across its entire surface. However, typical thin quartz (101̄1) crystal samples kept flat by direct attachment to a flat substrate reflect 8 keV x rays differently across their surface, on a scale comparable to the ideal rocking curve. Additional processing improves the uniformity. Irradiation of flat crystals with collimated, monochromatic x rays in rocking curve topography shows such problems directly, with microradian resolution. Nonuniform x-ray reflection is more difficult to document for strongly bent crystals because, then, monochromatic, collimated x rays satisfy the Bragg condition only along a narrow stripe that may be too narrow to resolve with the available cameras. However, it can be resolved with a knife edge that moves through the reflected x rays with the necessary spatial precision as demonstrated here for a bent silicon crystal. This shows qualitatively similar imperfections in the reflection as flat quartz and as the bent quartz analyzers reported on previously with lower resolution.