DESIGN OF MULTIMEGAWATT MILLIMETER-WAVE CONVERTERS FOR OPERATION AT HIGH GYROHARMONICS

A summary is provided of a feasibility study for the production of mul timegawatt RF power from a spatiotemporally modulated gyrating relativ istic electron beam at a high harmonic of the frequency of modulation, Parameters are given for optimizing the production of power at 148.5 GHz, the thirteenth harmonic of an 11.424-GHz cyclotron autoresonance traveling wave interaction that accelerates the beam, With an injected 16-A 200-kV beam, to which 7.2 MW is added in the accelerator, it is predicted that a power output of 2.2 MW at 148.5 GHz can be realized, after taking into account ohmic: wall losses, This requires an injecte d laminar beam with small initial axial velocity spread, and an output structure that effectively suppresses competing modes, In this device a tapered guide magnetic field no stronger than 8.2 kG is required, M eans to produce the required high-quality electron beam, and to allow only the TE(13,1) design mode to propagate in the output structure are discussed, A similar design for a fifteenth harmonic converter at 171 .4 GHz is also described.