Doppler-shift dominated cyclotron maser amplifiers

The Doppler shift-dominated cyclotron maser is a potential competitor with the gyrotron and free electron laser at mm and sub-mm wavelengths, in virtue of its tunability, high efficiency, and favorable frequency scaling with electron beam energy. The results of the fully relativistic electromagnetic particle code with absorbing longitudinal boundary conditions presently developed to study the performance of this device indicate that a relativistic electron beam with 750 keV energy, 3 kA current, 0.5 percent momentum spread, and 16-kG magnetic field, can amplify 90-GHz input signals with more than 25 percent efficiency and 30 percent nonlinear bandwidth. Attention is also given to the effects of electron beam momentum spread on performance.