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Summary form only given, as follows. For gyro-amplifiers, the collector often also serves as the RF output waveguide. The axial magnetic field in such collectors is tapered so that most of the beam electrons can be collected on the collector. Transverse kicker magnets are used as a barrier to prevent stray electrons from being intercepted by the dielectric RF window. This is to reduce the possibility of electron-induced damages for the RF windows. This procedure has been implemented in the collector of the recently developed NRL/Litton/CPI high-power, W-band gyro-amplifier. Using the gun code UGUN, it is shown that electron interception by the window is a possibility, even when the transverse kicker magnet is sufficient to deflect all the primary beam electrons away from the window. UGUN, which includes models for scattered primaries and true low-energy secondary electrons, was modified to treat the 3-D nature of the kicker magnet. It is found that the electron migration across the transverse magnetic field barrier is due to multiple bounces, forward-scattered primaries. Consequently, it is necessary for the kicker magnet design to take into account this effect to minimize the possibility of window damage. |
