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 appro-priate choice for the relevant parameters, the result-ing interaction is found to be extremely efficient, with efficiencies aooroachinq 100 oercent. and to possess a moderate frequency-upshift from-the non-relativistic gyrofrequency. The nonlinear theory of the interaction is outlined and preliminary designs are presented.