The development of high frequency, megawatt gyrotrons for ITER

The present focus of the MIT program is to demonstrate that efficient operation can be achieved with a gyrotron oscillator at power levels in excess of 1 MW and frequencies between 140 and 200 GHz. These are the operating parameters required for the International Thermonuclear Experimental Reactor (ITER) for plasma initiation, bulk heating, and current drive. Two major experiments are being conducted at MIT as part of this program: A 170 GHz, 1 MW gyrotron operating in the TE/sub 28,8,1/ mode using a conventional, tapered cavity, and a coaxial 140 GHz, 3 MW gyrotron oscillating in the TE/sub 21,13,1/ mode. This paper reviews design issues that were investigated during the construction of these experiments, and also presents results from initial operation of the coaxial gyrotron.