Mode competition and self-consistent simulation of a second harmonic gyrotron oscillator

A nonlinear numerical simulation of a second harmonic gyrotron oscillator i s presented in this paper. Mode competition from a competing fundamental mo de is investigated. In addition, a self-consistent nonlinear theoretical mo del, including the effect of velocity spread, is applied to analyze the sec ond harmonic gyrotron. A series of numerical calculations is carried out fo r different electron beam parameters. The results are compared with that of calculations using the cold-cavity, fixed field approximation and with exp eriments. Good agreement is found between our calculations and an experimen t at Fukui University. The azimuthal polarization of the field and the choi ce of the electron beam radius are also discussed.