Theoretical Study of the Effect of Electron Beam Misalignment on Operation of the Gyrotron FU IV A

In this paper, the theory describing the processes in gyrotrons with misaligned electron beams is used for interpreting some experimental results obtained in the FU IV A, 335-GHz gyrotron operating at the fundamental cyclotron resonance. The theory describes the effect of the beam misalignment on the single-mode operation in the small-signal (start currents) and large-signal (efficiency) regimes. It also describes the effect of the beam misalignment on the interaction between two oppositely rotating modes. Comparison of theoretical and experimental results demonstrates good qualitative agreement; in particular, both of them show that 0.3-mm misalignment of the beam axis causes efficiency degradation by a factor of two.