DESIGN OF A HIGH-ORDER VOLUME MODE CAVITY FOR A 1 MW 140 GHZ GYROTRON/

A high-power cylindrical cavity gyrotron operating at 140 GHz is studi ed. The possible working modes TE(22,4), TE(22,5) and TE(22,6) are com pared. The output power envisaged is 1 MW. The influence of the space charge effect of the electron beam and the RF losses in the resonator are discussed. Results of numerical calculations of the interaction of the electron beam and the RF wave are presented. The problem of singl e-mode excitation is addressed in mode competition calculations. Stabi lity regions of the working modes are shown for some interesting param eter ranges. From these plots an optimized variation of the parameters during start-up of the gyrotron can be deduced in order to ensure sin gle-mode operation. On the basis of kinetic theory the influence of mi salignment of the electron beam and resonator axis (eccentricity) on t he starting currents and frequency shifts of the operating and parasit ic modes is studies for several values of eccentricity.