DIII-D High Field Side Lower Hybrid Current Drive Experiment Status*

High field side lower hybrid current drive (HFS LHCD) is potentially an efficient off-axis current drive tool, r/a~0.6-0.8, for advanced tokamak DIII-D discharges. LH waves launched from HFS are expected to bridge the spectral gap through mode transformation from slow to fast back to slow wave resulting in improved accessibility and single pass absorption due to favorable wavenumber upshift. A compact coupler has been designed utilizing a traveling wave, 4-way splitter and a multi-junction to distribute power poloidally and toroidally, respectively, and has imbedded matching structures to maximize performance. The imbedded matching elements required additive manufacturing and post processing to achieve the desired RF voltage and loss characteristics. The HFS LHCD coupler and waveguides have been installed in the DIII-D tokamak. Prior to operation, vacuum issues arose after machine bake and have prevented RF operation into plasma. A new design to accommodate differential expansion between the waveguides and the machine has been analyzed and is planned to be implemented at the first opportunity. Klystron commissioning has progressed well and the klystrons have been operated up to 400 kW, 1 s into dummy load. The latest analysis, results and system status will be presented.