A High-Power, Broadband Window for Step-Tunable Gyrotrons

Step-tunable gyrotrons are desired for electron cyclotron heating and suppression of instabilities in tokamak fusion plasmas. High power tunable gyrotrons are in development in various countrie; however, attempts to develop a high power, broadband vacuum window to transmit the power have been unsuccessful. CVD diamond appears to be the only material capable of transmitting the 1 MW CW power required. Implementation of diamond windows in the current gyrotron configuration is impractical due to window size and cost issued. Calabazas Creek Research, Inc. recently developed an innovative technique for converting RF power inside the gyrotron directly into HE11 waveguide. This reduces the diameter of the RF beam and allows implementation of a Brewster angle window. The size of the diamond material required is comparable to that of existing windows for single frequency gyrotrons. Commercial Applications and Other Benefits: High power RF sources are desired for improved heating and instability suppression in most all tokamak devices. If successfully developed, these windows would likely be implemented in all future, high power, step-tunable gyrotron in the U.S., Europe, and Asia