Improved collectors for high power gyrotrons

High power gyrotrons are used for electron cyclotron heating and current drive in tokamak plasmas. These sources operate with typical efficiencies between 35-50%. For gyrotrons producing one megawatt of RF power, at least one megawatt of electron beam power must be dissipated in the collector. To disperse this power over a larger region, a cyclically varying magnetic field sweeps the spent beam axially along the collector surface. This reduces the average beam power in a specific region; however, cyclic fatigue of the metal surface is causing collector failures. This research is addressing this problem by exploring alternative collector configurations and materials. New configurations reduce the peak power densities below levels requiring collector sweeping, and material improvements increase the predicted lifetime by an order of magnitude.