Ultra-thin curved transmission crystals for high resolving power (up to E/ΔE = 6300) x-ray spectroscopy in the 6-13  keV energy range.

Ultra-thin curved transmission crystals operating in the Cauchois spectrometer geometry were evaluated for the purpose of achieving high spectral resolution in the 6-13 keV x-ray energy range. The crystals were silicon (111) and sapphire R-cut wafers, each 18 mu m thick, and a silicon (100) wafer of 50-mu m thickness. The WL alpha(1) spectral line at 8.398 keV from a laboratory source was used to evaluate the resolution. The highest crystal resolving power, E/Delta E = 6300, was achieved by diffraction from the (33-1) planes of the Si(100) wafer that was cylindrically bent to a radius of curvature of 254 mm, where the (33-1) planes have an asymmetric angle of 13.26 degrees from the normal of the crystal surface facing the x-ray source. This work demonstrates the ability to measure highly resolved line shapes of the K transitions of the elements Fe through Kr and the L transitions of the elements Gd through Th using a relatively compact spectrometer optical system and readily available thin commercial wafers. The intended application is as a diagnostic of laser-produced plasmas where the presence of multiple charged states and broadenings from high temperature and density requires high-resolution methods that are robust in a noisy source environment.