Design of a high-resolution x-ray crystal spectrometer for SPARC

We present a scoping study conducted to characterize the performance of a high resolution, x-ray crystal spectrometer intended to measure ion temperature and toroidal rotation in the SPARC tokamak. Given the expected electron temperature and density profiles, we have chosen some candidate transitions in seeded Xe, Kr, and intrinsic W (tungsten walls). Multiple lines need to be used to provide complete coverage which would require changing the crystal and Bragg angles. Emissivity profiles for the selected line radiation were modelled using the Aurora code and benchmarked against FLYCHK. Spectrometer geometry and choice of diffraction crystal were also considered to estimate the expected signal at the detector. Beryllium windows needed to be placed along the beamline due to D/T compatibility, so number and thickness was scoped to avoid significant loss of signal. Dose at the crystal had to also be evaluated due to the high neutron flux environment of a burning plasma. This diagnostic is intended to be installed and ready for SPARC operations day one