Numerical simulation of a processes in the cavity of 170 GHz/CW/1 MW gyrotron for iter

We study two versions of a gyrotron operating in the TE^sub 28.7^ and TE^sub 31.8^ modes for electron-cyclotron heating of plasma in the international thermonuclear reactor ITER. The gyrotron cavity parameters are optimized allowing for ohmic losses, dips in electron beam potential, and velocity spread. The influence of the ion compensation for the space charge, the setting of oscillations at when the gyrotron is switched on, and the competition between the operating and parasitic modes are discussed. The possibility of attaining an efficiency of 32 to 36% for a specific power of ohmic losses in the cavity of less than 2.5 kW/cm^sup 2^ in the TE^sub 28.7^ mode and 2 kW/cm^sup 2^ in the TE^sub 31.8^ mode is demonstrated.[PUBLICATION ABSTRACT]