Gyrotrons for technological applications

Abstract A review is given of the possible uses of gyrotrons in industry. A comprehensive theoretical study of mode selection, mode competition, and resonator design for industrial gyrotrons is performed. It is shown that the TE02 mode at the second harmonic and the TE03 mode at the third harmonic are good candidates for the operating mode in an industrial gyrotron. Starting currents for these modes and modes oscillating at lower harmonics are calculated, and mode competition is examined on the basis of the nonlinear non-stationary theory. It is emphasized that in industrial gyrotrons, owing to a relatively large length of the cavity, it is possible to increase significantly the electron efficiency by introducing inhomogeneity into the profile of the guiding magnetic field in a cavity. The important issue of the negative influence of electron velocity spread on the efficiency is studied quantitatively both for tapered and untapered magnetic fields, This is of interest also for gyrotrons used for fusion pl...