Demonstration of high efficiency 1MW oscillation by 170GHz CW Gyrotron

A 1MW 170GHz long pulse gyrotron is required for a power source of an electron cyclotron heating and current drive (EC H&CD) system on ITER (International Thermonuclear Experimental Reactor). After the R&D works of 15 years in Engineering Design Activities (EDA) of ITER a stable 1MW 170GHz oscillation has been attained at CW- relevant pulse duration (800s). The efficiency was 55 % with the depressed collector in the hard self-excitation region. These parameters fully satisfy the ITER requirement. The results will push the EC H&CD using a high power mm wave to the major tool of plasma heating and its instability control for ITER and followed fusion reactor.