Nonstationary Theory of Mode Competition in Gyrotrons with Allowance forInhomogeneity of the Guiding Magnetic Field

摘要

High-power millimeter wave generators can induce electron cyclotron waves in aplasma which can fulfill many functions (plasma breakdown, heating, current drive) in fusion plasma reactors including both tokamak and stellarator concepts. All these applications require tons of megawatts of power in the frequency range 100-300 GHz and power 0.5-1.5 MW per unit. Among various microwave sources, gyrotrons are the most developed source. Because of the heat losses in resonator walls at such high frequencies and powers, oversized cavities must be used. In such cavities, the mode competition becomes a severe problem. The most advanced theory of mode competition in gyrotrons in the nonstationary nonlinear theory. In the present paper, the authors extend this theory by allowing for inhomogeneity of the guiding magnetic field. The importance of this generalized theory is illustrated in the case of a 3 MW 140 GHz gyrotron with a coaxial cavity working in the TE(21,13) mode.