Electrically Tunable Four-Mirror Gyrotron with Crossed Fields

In a four-mirror gyrotron, a wide multi-screw electron beam, being in crossed electric and longitudinal magnetic fields, drifts with a velocity v d = E 0 / B 0 in the direction of the T -wave propagation between the resonator mirrors (co-current wave) or in the opposite direction (counter-propagating wave). In this case, in accordance with the Doppler effect, the generation frequency ω is determined from the synchronism conditions as ω ≈ k ω l (1±β d ), β d = v d / с . Thus, a change in E 0 changes ω, i. e. electrical frequency tuning is carried out. The article presents a diagram of the design of a two-beam four-mirror gyrotron. The calculations were carried out for β d = 0.5, q = β || /β ⊥ = 2, the interaction was carried out at the frequency harmonic number k = 1. The tuning band was 20 %. The maximum efficiency is 48 %, the minimum is 33 %. Since the calculations were performed for dimensionless parameters, i.e., having a universal character, the physical characteristics of the gyrotron at a wavelength λ = 6 mm ( f 0 = 50 GHz) and a loaded resonator quality factor Q l = 200 were as follows: electron beam current I 0 = 60 A, B 0 = 2 T, voltage U 0 = 79 kV, efficiency = 48 %.