A novel hybrid slow-wave/fast-wave traveling-wave amplifier

We introduce a new broad-band amplifier configuration which contains elements of both linear and cyclotron resonance maser microwave tubes. A helix slow-wave structure is used to bunch a linearly streaming annular electron beam. A nonadiabatic magnetic transition, which is placed after a drift region at the point where the ac beam current is nearly maximized, converts much of the beam's axial momentum to rotational momentum. The beam then travels through a tapered right-circular waveguide, where microwave energy is extracted via the gyrotron interaction. The design of a proof-of-principle X-band amplifier is given, and the codes that are used in the simulation are described. The nominal beam voltage and current are 45 kV and 8 A, respectively. The tube is predicted to be stable, to possess a peak efficiency above 43%, and to have an instantaneous bandwidth of over 9%.