Studies on a 120 GHz, 1.0 MW, longpulse gyrotron for plasma start-up in ITER

In this work, the initial design concept of a 1.0-1.5 MW, longpulse gyrotron operating at 120 GHz, for plasma start-up in the ITER has been presented. Mode competition and mode selection procedures are carried out for various candidate modes and the modes TE_24,8 or TE_24,7 are chosen as probable operating modes. Cold cavity design and self-consistent and time dependent calculations are carried out for the TE_24,8 mode and power and efficiencies are computed. The nominal beam parameters are chosen to give a moderate to low velocity spread. The initial results are indicating that an output power of well over 1.0 MW, CW can be achieved at 120 GHz with the TE_24,8 mode as the operating cavity mode. Further investigations to consolidate the design concept are in progress at the time of reporting this paper.