Simulation of beam collector nonuniformities in gyro-amplifiers

The spiraling beams employed in gyro-amplifiers can create regions of enhan ced local heating on the beam collector surface as a result of the turning- point behavior of the electron orbits. Although guiding center spread and t he spread in Larmor radii will usually smooth out these irregularities, hot -spotting can reappear as a result of small transverse displacements or ang ular misalignments between the collector axis and the system magnetic axis, or from transverse magnetic fields in the electron gun. This paper present s a new, general procedure to efficiently simulate the spatial distribution of electron impacts in misaligned gyro-amplifier beam collectors, using ad iabatic theory and analytic geometry. The procedure is used to investigate the distributions associated with various types of misalignments and the re sults are compared with experimental collector maps obtained from a high-av erage power, 94-GHz gyroklystron.