Influence of crystal thickness on reflectivity and energy resolution for transmission crystals

The spectrometer calibration station (SCS) at Lawrence Livermore National Laboratory allows us to characterize and calibrate various crystals for different x-ray spectrometer geometries regularly used at the National Ignition Facility (NIF). Absolute throughput measurements are essential to properly diagnose the sources and extract meaningful results about the emitting plasma. Additionally, the SCS can help optimize instruments by testing different crystals. The Imaging and Spectroscopy Snout (ISS) is a NIF diagnostic that can be equipped with up to four different transmission crystals, each offering energy ranges from ~7.5 keV to ~12 keV with different energy resolutions. One critical parameter in such geometry is the crystal thickness. We present here an experimental study on the SCS comparing the integrated reflectivity and the spectral resolution measured for various unique ISS Quartz crystal thicknesses. The results will be discussed in the context of optimizing ISS measurements for ICF and will also be compared with theoretical calculations using pyTTE.