Enhancement of high-harmdnic gyrotron gain by a dielectric rod

Abstract

A dielectric rod is shown to reduce the energy requirements of the electron beam for high-harmonic gyrotron operation. A large interaction filling factor can occur for moderate-energy electrons (∼ 80 keV) spiralling around the rod within the evanescent region of a dielectric waveguide mode. Since the magnetic field strength is reduced by an order of magnitude in an interaction at the tenth harmonic of the cyclotron frequency, a submillimeter-wave gyrotron is now truly feasible because the acceleration voltages can be conveniently produced by DC power supplies.