Electrically Tunable Four-Mirror Gyrotron with Crossed Fields

Abstract

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 = E₀ /B₀ 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 ≈ kω_l(1±β_d), β_d = v_d /с. Thus, a change in E₀ 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 (f₀ = 50 GHz) and a loaded resonator quality factor Q_l = 200 were as follows: electron beam current I₀ = 60 A, B₀ = 2 T, voltage U₀ = 79 kV, efficiency = 48 %.