Steady State Operation of High Power Gyrotron for ITER

A steady-state operation of 1 MW/800 s with the efficiency of 55%, which exceeded 1 MW/400 s of the performance required in ITER, was demonstrated in 170 GHz gyrotron. The oscillation characteristics in the long pulse operation was clarified, and the advanced operation scenario of the gyrotron to the high efficiency oscillation was newly established by controlling a pitch factor of the electron beam and the cavity magnetic field in the long pulse operation. In the long pulse experiment, the steady state operation of 1 hour with the output power of 0.6 MW was also demonstrated.