Cyclotron Maser and Peniotron-Like Instabilities in a Whispering Gallery Mode Gyrotron

The efficiency of the mth harmonic electron cyclotron maser interaction for a TE/sub mn1/ gyrotron oscillator is compared with the (m-1)th harmonic peniotron-like interaction. Identical cavities and electron beams are used. Start oscillation conditions from weak-field linear theory are given, as well as optimized nonlinear efficiencies. The peniotron-like interaction leads to optimized efficiencies of /spl lsim/= 65 percent, while those for the electron cyclotron maser interaction are limited to /spl lsim/=25 percent in the cases studied.