Theory of the anomalous Doppler cyclotron-resonance-maser amplifier with tapered parameters

The theory of a slow-wave cyclotron-resonance-maser (CRM) amplifier employing an initially linear electron beam is developed. In such a device, the electrons radiate electromagnetic waves under the anomalous Doppler effect. In order to maintain the cyclotron resonance between the radiating electrons and the amplifying electromagnetic wave, we consider a system with tapered waveguide parameters. The self-consistent set of equations results in one equation describing the efficiency of the anomalous Doppler CRM interaction as a function of the waveguide length. The efficiency limit approaches 100% in the ideal case. A practical scheme of the anomalous Doppler CRM amplifier is proposed as a stripline waveguide with a slight tapering of the strip width. This scheme is analyzed numerically, and it is shown that the efficiency of this device may exceed 30%.