Theoretical Analysis of the Stability of the Single-Mode Generation Regime in the Gyrotron

We discuss the question of the stability of the single-mode generation regime in the gyrotron. An example of a gyrotron with the fixed Gaussian structure of the high-frequency field is used to analyze theoretically the instability mechanism during the interaction of modes with the quasiequidistant spectra on the assumption that the amplitudes of the spurious modes are low. The boundaries of the stability domain for the operating mode on the parameter plane “cyclotron resonance mismatch—normalized current parameter” are plotted at various densities of the mode spectrum. It is shown that at growing mode spectrum density, the structure of the stability domain of the operating mode becomes complicated and the domain dimensions become smaller. The boundaries obtained theoretically agree well with the results of the calculations within the framework of the multimode gyrotron theory.