A Low-Cost, High Power RF Resonance System for Plasma Diagnostics and Heating

Due to the high cost and complexity of RF heating systems, which typically require high power gyrotrons or klystrons, associated power supplies, wave guides and vacuum systems, they are rarely available for the small-scale validation experiments. The charter for the small scale Validation Platforms Experiment VPE) community is to advance our level of knowledge in plasma physics and control to support the larger tokomak experiments and the entrance into the burning plasma era. Significant progress in transport, instability control and the underlying plasmas physics could be gained if the VPE community had access to high power RF heating systems at costs that can be supported under current funding levels. In the past work on alternative HPRF systems, using nonlinear transmission line NLTL) technology was encouraging; however, it lacked a high voltage driver with the correct rise times, pulse width and pulse repetition frequencies necessary to produce output power levels needed to support fusion science experiments. Eagle Harbor Technologies has created new high voltage nanosecond pulser, which combined with NLTL technology will produce a low-cost, fully solid state architecture for the generation of the RF frequencies and power levels necessary for plasma heating and diagnostic systems within the VPE fusion science community. The proposed system does not require the use of vacuum tube technology, is inherently lower cost, and is more robust the traditional high power RF heating schemes. The program will directly support the small-scale validation experiments, where the new system will be designed to be installed onto the HIT-SI experiment at the University of Washington, which will utilize the system as a heat pulse diagnostic for the determination of the transport mechanisms within HIT-SI. In the Phase I program, EHT will design, build, and test a high voltage nanosecond pulser system with a suitable NLTL. The new system will be designed for pulsed high power heating for utilization in the fusion science experimental community. EHT will collaborate with a DOE supported VPE HIT-SI) to incorporate and test the system for pulsed plasma heating on that experiment. System scaling will also be conducted to determine architectures and costs for a second generation system capable of supporting the larger VPE and tokomak fusion community. High power radio frequency generation using vacuum tube based system is widely utilized in the scientific community, military and industry. Vacuum tube technology is fully mature with little expected advancement in robustness and simplicity for these systems. There is a wide need for new technologies for RF generation which can increase capabilities while reducing cost and complexity. Additionally, the new nanosecond pulser has demonstrate utility in the creation of low temperature plasmas which have applications in surface decontamination, materials processing, UV light generation and several novel medical applications including cancer treatment. Continued support of the nanosecond pulser technology alone could have wide ranging benefits in these areas.