Highly efficient blazed grating with multilayer coating for tender X-ray energies

For photon energiesof 1 – 5 keV, blazed gratingswith multilayer coating are ideally suited for the suppression of stray and higher orders light in grating monochromators. We developed and characterized a blazed 2000 lines/mm gratingcoated with a 20 period Cr/C- multilayer. The multilayer d-spacing of 7.3 nm has been adapted to the line distance of 500 nm and the blaze angle of 0.84° in order to provide highest efficiency in the photon energy range between 1.5 keV and 3 keV. Efficiency of the multilayer gratingas well as the reflectance of a witness multilayer which were coated simultaneously have been measured. An efficiency of 35% was measured at 2 keV while a maximum efficiency of 55% was achieved at 4 keV. In addition, a strong suppression of higher orders was observed which makes blazed multilayer gratingsa favorable dispersing element also for the low X-ray energy range.