Development of a Multi-Stage Depressed Collector System For Gaussian Mode Gyrotrons

185 Development of a Multi-Stage Depressed Collector System For Gaussian Mode Gyrotrons--Calabazas Creek Research, 20937 Comer Drive, Saratoga, CA 95070-3753; (408) 741-8680 Dr. R. Lawrence Ives, Principal Investigator Dr. R. Lawrence Ives, Business Official DOE Grant No. DE-FG03-97ER82342 Amount: $75,000 Several organizations are developing gyrotrons for electron cyclotron resonance heating for current and planned fusion experiments, including the International Thermonuclear Reactor Experiment. Because the circuit efficiencies of gyrotrons are typically around 35%, it would be advantageous to recover the wasted power to improve the overall efficiency, thereby reducing operating and electrical capacity costs. Development of a single system applicable for a wide range of frequencies and power levels will also dramatically lower the cost of gyrotron development and manufacture. This project will develop a complete depressed collector system including the collector subassembly, power supplies, and control software applicable to Gaussian mode gyrotrons operating between 110 gigahertz and 170 gigahertz at power levels up to 1 megawatt continuous wave. In Phase I, the collector design achieved in a previous SBIR program at 170 gigahertz will be modified to allow use at frequencies between 110 gigahertz and 170 gigahertz. Advanced techniques for addressing reflected and back-scattered electrons will also be investigated. Based on the information obtained, specifications will be developed for a complete solid-state power supply system. Control software will also be developed to ensure optimum performance under anticipated operating conditions. During Phase II, a complete system, including collector, power supplies, and control software, will be built and tested on a production gyrotron. Commercial Applications and Other Benefits as described by the awardee: The applicability of the system to a broad range of gyrotron products will significantly reduce the cost of gyrotron development and manufacture. The lower operating costs from increased gyrotron efficiency, reduced thermal dissipation, and the availability of lower cost, solid-state power supplies will make the system attractive for all applications requiring high-frequency radio frequency power. Given the forecasts for large numbers of gyrotrons for upcoming fusion experiments, the commercial potential is quite significant.