Theory of gyrotron amplifier in a tape helix loaded waveguide

Stability properties of the cyclotron maser instability in an annular electron beam propagating through a cylindrical waveguide loaded with a tape helix are investigated, in connection with applications on the gyrotron amplifier. Closed form of the dispersion relation for the cyclotron maser instability is obtained, including influence of the tape helix in stability behavior. It is shown that the bandwidth of the gyrotron amplifier for a tape helix is narrow in comparison with results for a sheath helix. However, the growth rate of the tape helix gyrotron is comparable to that of the sheath helix gyrotron.