Status of the HFS LHCD System on DIII-D

The DIII-D High Field Side (HFS) Lower Hybrid Current Drive (LHCD) System will validate a novel approach for RF noninductive off-axis current drive for r/a~0.6-0.8 . The launcher centerpost placement improves wave accessibility and penetration while reducing plasma interaction issues and associated coupler damage.

A 2 MW power system with eight 4.6 GHz klystrons has been installed. The high voltage power supply, cooling water circuits, and instrumentation and control commissioning has been completed, while the eight klystrons commissioning and conditioning is underway. All the eight klystrons are operated with power injection in the dummy loads with power above 20 kW for each system. The pulse length was extended to 100 ms for all eight systems and klystron conditioning continues to increase pulse length and output power. The system is expected to be ready for experiments in FY24.

The LHCD HFS launcher components and in-vessel waveguides were additively manufactured (AM) GRCop-84. The waveguide and launcher assembly has been temporary installed on a 1:1 scale representation of the DIII-D centerpost. The LHCD instrumentation and diagnostics include: optical arc detection, impurity monitor for plasma-material interaction, pyrometer to monitor thermal response , thermocouples, visible camera monitors, Langmuir probes, and reflectometer for density profile measurements. The latest progress on klystron commissioning and coupler installation will be presented.