CW, high power, gyrotron development at 110 GHz for ECH applications

Electron cyclotron heating (ECH) is the most promising plasma heating method to achieve fusion. High-power, long-pulse or CW gyrotrons are required in many present and future ECH experiments. For example, the planned experiment at DIII-D, the experimental tokamak at General Atomics, will require 4 MW of RF power at 110 GHz for a pulse duration of 10 seconds. The RF requirement for the planned International Thermonuclear Experimental Reactor (ITER) is 50 MW at 170 GHz and CW operation. CPI is developing high-power, CW gyrotrons at frequencies ranging from 84--170 GHz for various ECH experiments. In particular, the authors are developing a 1 MW, CW gyrotron with an internal converter at 110 GHz. To achieve the goal of 1 MW, CW operation, the authors have designed and begun fabrication of a new tube that has improved cooling to all tube parts which showed signs of overheating during the last experiment. In addition, they are looking at the possibility of using alternate output window designs to increase power handling capability. They summarize the design of the new tube and present initial test data