Design of a high-efficiency low voltage axially modulated cusp-injected second-harmonic x-band gyrotron amplifier

Abstract

We present the theoretical design of a secondharmonic small-orbit gyrotron amplifier which utilizes the interaction between a 35-kV 4-A beam and a TEoll cavity to produce over 70 kW of amplified power at 9.9 GHz in a 1.83-kG magnetic field. One of the novel features of this device is that the electron gun produces an axially streaming annular beam which is velocity modulated by a short TMono input cavity. Perpendicular energy is imparted to the beam via a nonadiabatic magnetic transition at the end of a 13-cm drift region. An electronic efficiency of 53% is predicted with a large signal gain near 20 dB by a single particle code which takes into account nonideal effects associated with finite beam thickness and finite magnetic field transition widths.