A new concept for generation of multi-megawatt power approaching hundred percent conversion efficiency

The paper describes a new principle of microwave tube with promise of generating very large power with extremely high efficiency, approaching one hundred percent. The principle might lead to novel designs of multi-megawatt tubes supplying microwave power for particle accelerators, for fusion research, and in future satellite solar power stations. A low perveance electron beam is modulated transversely in a circularly polarized pattern, analogous to the beam in a cathode ray tube with 90 degrees out of phase voltages at the deflection plates. The spiraling beam interacts with the rf fields in the output traveling wave ring resonator, which is coupled to the external load by a circumferential directional coupler. The theoretical conversion efficiency for a thin beam is one hundred percent, but less for a finite diameter practical beam. Details of modulation pattern, beam spread, and expected efficiency are presented in the paper.