Nonuniform cathode emission studies of a MIG gun

We present results on the first full 3D modeling of a magnetron injection gun (MIG) to study emission nonuniformity using the MICHELLE 3D code. The results indicate the effects of nonuniform current emission on velocity spread and pitch factor. Nonuniform emission has been shown to be detrimental to the efficiency of gyrotron operation. The model is based on a 96 kV, 40 A MIG used in a 110 GHz, 1.5 MW gyrotron experiment operating in short pulses at MIT and in long pulse/CW mode at CPI. The MIT gyrotron uses capacitive probes to determine the azimuthal variation in the pitch factor to compare with simulation.