Theoretical and experimental studies of cyclotron autoresonance Maser amplifiers

Recent advances in the theory of cyclotron autoresonance maser (CARM) amplifiers and comparisons between the theory and experiments are reported. Emphases are placed on the linear and nonlinear analysis of the CARM interaction with multiple transverse waveguide modes in overmoded systems. General features of multimoding effects on the amplifier performance are discussed. Techniques for efficiency enhancement have been developed, and the effects of longitudinal space-charge waves on the cyclotron resonance maser instability are analyzed. Good agreement has been found between the theory and the results from 35 GHz CARM amplifier experiments which have produced rf power of 12 MW, corresponding to an electronic efficiency of 6%.