Theoretical investigations on the fast and mixed wave modes for plasma-filled gyrotrons

The effect of a cold plasma column inside a gyrotron amplifier on a fast wave mode and a mixed wave mode was worked out. The linear dispersion relation was derived with the Vlasov-Maxwell´s equation for the hollow and thin electron beam. The effects of the beam location, electron beam parameters and azimuthal harmonic number on the growth rate for both the fast and mixed wave modes were carried out. It is shown that the growth rate and bandwidth of the mixed wave mode is larger than that it is for the fast wave mode.