Edge Scanning Reflectometry on SPARC

Edge scanning reflectometry (ESRL) on SPARC aims to determine the ICRF evanescent layer location and thus help assess the ICRF antenna loading, and also to measure H-mode pedestal density profiles. ESRL uses a standard frequency sweep technique covering the range from 18 GHz to 120 GHz. Both O-mode and left-hand-cutoff (LHC) X-mode will be implemented. For B₀ ~ 12 T, the cutoff density ranges from ~0.4e19 m^-3 to ~6e20 m^-3. There are 2 pairs of horns for O-mode and 2 pairs for X-mode. Considering the relatively short distance (~20 m) from the diagnostic hall to the tokamak, we plan to use overmoded waveguides to minimize signal loss while allowing system flexibility. The horn antennas are optimized with COMSOL RF modeling. EM load analysis and thermal analysis will be presented. The mm-wave and IF electronics have been analyzed and optimized based on synthetic reflectometry data. The latest status of the project will be presented.