Simulation of beam collector nonuniformities in gyro-amplifiers

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