Collisional multipactor inside ambient gas

The influence of collisions during rf-induced multipactors in the presence of ambient gas is studied in some detail. The effect of the randomization of the electron rf-interaction phases due to collisional kicks is given particular emphasis, since phase locking among successive generations of rf-driven electrons is essential for avalanching. The systematic collisional friction shifts the parameter region for multipactor eruption to higher rf-fields compared to vacuum. Random velocity fluctuations prevent convergence to exact phase locking, causing the impact phase to wander around its nominal resonant value. The rms width of the phase spread is determined by the balance between the rf-induced dynamical phase focusing and random phase diffusion. For low collision frequencies phase wandering in the unfavorable for secondary emission regime reduces the effective secondary yield and may eventually cause multipactor quenching. For high collision frequencies multipactor is completely suppressed due to loss of c...