High average power microwave sources for fusion research

Fusion research requires heating plasmas confined by intense magnetic field to high temperatures where thermonuclear reactions can take place. From a reactor point of view, operation of Tokamaks with noninductive currents using Electron Cyclotron Resonance Heating (ECRH) is also important. Among many concepts, gyrotrons have uniquely met the needs of the program and continue to excel, meeting the increasing demand for high average power sources. The industrial gyrotrons in the mid 70´s were rated at 28 GHz, 200 kW, CW as compared to CPI´s current 110 GHz gyrotrons rated at 1 MW, CW. This presentation concentrates on the advances which lead to these achievements, in particular, the principle of operation, and design considerations of gyrotrons.