A Classical Electron-Cyclotron Maser with Axial Electron Beam Injection

It is shown that the Electron-Cyclotron Maser interaction can be made compatible with exclusively axial injection of the electron beam, by introducing an appropriate slow-wave structure. With an appropriate choice for the relevant parameters, the resulting interaction is found to be extremely efficient, with efficiencies approaching 100 percent, and to possess a moderate frequency upshift from the nonrelativistic gyrofrequency. The nonlinear theory of the interaction is outlined and preliminary designs are presented.