Prospects of Developing Multi-Megawatt Gyrotrons for Bulk Heating of Controlled Thermonuclear Reactors

Nearly 20 years have elapsed since basic theoretical and experimental studies confirmed the validity of the electron cyclotron maser gain mechanism. The leading effort in exploiting this knowledge to develop a new class of millimeter-wave oscillators at uniquely high power levels was made in the Soviet Union. This effort led to the announcement in 1974 of efficient kilowatt-level, CW gyrotron oscillators at millimeter and submillimeter wavelengths [1], and in 1978 to the announcement of megawatt long-pulse devices at 3 and 6.7 mm wavelengths [2]. An effort in the U.S. has also been set into motion to produce gyrotron oscillators for fusion plasma heating experiments. Gyrotrons producing kJ pulses of energy have been developed by Varian Associates at 28 GHz [3], and by the Naval Research Laboratory (NRL) at 35 GHz [4]. The latter device is presently being deployed in electron-cyclotron-resonance-heating (ECRH) experiments.