Mechanisms of amplification of ultrashort electromagnetic pulses in gyrotron traveling wave tube with helically corrugated waveguide

TLDR

The study models short‑pulse amplification in a gyrotron traveling wave tube with a helically corrugated waveguide, examining grazing and intersecting dispersion regimes between the electromagnetic wave and the electron beam. The theory predicts distortion‑free amplification for pulse widths matching the gain bandwidth, shows that electron–wave slippage can feed unmodulated electrons, and that optimal parameters can yield output pulses exceeding the saturated amplitude and even surpass the electron beam’s kinetic power.

Abstract

A time-domain self consistent theory of a gyrotron traveling wave tube with a helically corrugated operating waveguide has been developed. Based on this model, the process of short pulse amplification was studied in regimes of grazing and intersection of the dispersion curves of the electromagnetic wave and the electron beam. In the first case, the possibility of amplification without pulse form distortion was demonstrated for the pulse spectrum width of the order of the gain bandwidth. In the second case, when the electrons' axial velocity was smaller than the wave's group velocity, it was shown that the slippage of the incident signal with respect to the electron beam provides feeding of the signal by “fresh” electrons without initial modulation. As a result, the amplitude of the output pulse can exceed the amplitude of its saturated value for the case of the grazing regime, and, for optimal parameters, the peak output power can be even larger than the kinetic power of the electron beam.