Gyrotron amplifier in a helix loaded waveguide

Abstract

Stability properties of the cyclotron maser instability in a relativistic annular electron beam propagating through a cylindrical waveguide loaded with a sheath helix are investigated, in connection with application to the gyrotron amplifier. The stability analysis is carried out, assuming that the beam is thin and tenuous. A closed form of the dispersion relation for the cyclotron maser instability is obtained, including the influence of the sheath helix on stability behavior. One of the most important features in this analysis is that the bandwidth of the gyrotron amplifier for a helix mode is very broad. Moreover, it is also shown that for an appropriate choice of the helix radius and pitch angle, the maximum gain of the gyrotron amplifier for a hybrid wave is twice that for an ordinary waveguide.