Small-signal analysis of the induced-resonance electron-cyclotron maser

The induced-resonance electron-cyclotron maser operates at Doppler-upshifted frequencies ω≃${\gamma }^2$ ${\Omega }_0$, with γ the relativistic factor and ${\Omega }_0$=${\mathrm{eB}}_0$/γmc. In addition, the mechanism is insensitive to the beam thermal spreads when the index of refraction n=$k_z$c/ω is properly adjusted. A set of simplified equations, describing the electron dynamics near the axis of the configuration, is derived in the limit of small Larmor radius. The linear efficiency is derived for radiation having a Gaussian profile and propagating at an angle α relative to a constant external magnetic field. The start-up current for operation in the submillimeter regime is well within the capabilities of today’s long-pulse relativistic electron beams.