The Performance Test and the Improved Design of 28 GHz 1 MW Gyrotron

For the GAMMA10 tandem mirror, a 28 GHz 1 MW gyrotron has been developed. The output power was achieved 1 MW in short pulse test, and 0.54 MW / 2 s in long pulse test. Moreover, the temperature rise of sapphire single disk window installed in 28 GHz 1 MW gyrotron was measured. The temperature rise was 9 K at 0.45 MW / 2 s. On the basis of the results of the performance test, the designs of 28 GHz 1 MW gyrotron have been improved to enable the operation of 1.5 ~ 2.0 MW several sec. required in GAMMA10 and NSTX, and 0.4 MW CW required in QUEST.