, John F. Seely, Eric Galtier, Uri Feldman, Albert Henins
A Cauchois type spectrometer utilizing the (203) lattice planes at an oblique angle of 11.53o to the surface of a quartz transmission crystal recorded the Kα and Kβ spectral lines of six elements from Fe to Ag in the 6 keV to 22 keV energy range from a laboratory x-ray source. After deconvolving the natural lifetime widths and the image-plate detector broadening from the observed spectral line widths, the intrinsic crystal resolving power was determined to be 4000 at the lower energies and decreasing to 1000 at the higher energies. Previously, a Si wafer crystal exhibited twice this resolving power when the (331) planes had been used in asymmetric geometry. The investigation of diffraction with this quartz crystal, with a very similar lattice spacing and therefore spectral coverage, was motivated by the much larger integrated reflectivity of quartz due to its well-known quasimosaicity upon elastic bending. The measured spectral line widths were in good agreement with the widths calculated by accounting for various broadening mechanisms including source size, crystal thickness, crystal height, crystal rocking curve width, geometrical aberrations, and possible spectrometer configuration errors. Based on these results, Cauchois spectrometers employing asymmetric planes of perfect quartz and silicon crystals can be reliably designed and optimized for high resolution spectroscopy in the > 6 keV energy range.
crystal spectroscopy, crystal resolving power, x-ray