Design and Status of a High Field Side Reflectometer on DIII-D

A high field side (HFS) reflectometer will provide measurements of plasma density in the HFS scrape-off-layer (SOL) of the DIII-D tokamak. This diagnostic is in support of the upcoming HFS lower hybrid current drive (LHCD) experiment on DIII-D. The coupling of LHCD power to the core of the plasma for efficient current drive is extremely sensitive to the plasma conditions in the SOL local to the LHCD launcher. Reflectometry allows for measurement of the plasma density in the region of the LHCD launcher with high temporal and spatial resolution. These results will provide key insights into the study of LHCD coupling and LHCD-SOL interaction for the novel HFS LHCD experiment scheduled for operation in FY23. The reflectometer will operate in the O-Mode configuration in the 6-27 GHz range and is planned to be installed in early FY22. To compare with experiment, full-wave simulations of the HFS SOL and LHCD launcher have been performed in Petra-M, and these results are then coupled to the GENRAY/CQL3D package for core physics. This allows for the accurate simulation of the entire LHCD process from launcher to core current drive. An overview of the HFS reflectometer's design as well as the latest simulation results and current installation progress will be presented.