Mixed slow wave operation of a wide band dielectric gyrotron

The bandwidth broadening effect of mixing two slow wave modes in a dielectric loaded gyrotron is investigated for a small axial momentum spread. The usual intermediate wavelength model (IWM) combines with the short wavelength mode (SWM) by reducing the electron beam radius and creates a mixed slow wave. The resulting bandwidth for the mixed mode gyrotron becomes at least twice broader than that for the pure IWM at the small velocity spread (about but less than 1%) with a substantial contribution of the SWM. Moreover, the mixed mode operation can allow up to several times more power than the usual IWM mode operation.