Phase space analysis of multipactor saturation in rectangular waveguide

Abstract

In certain high power RF systems multipactor cannot be avoided for all operating points, but its existence places limits on performance, efficiency, lifetime, and reliability. As an example multipactor in the input couplers of superconducting RF cavities can be a major limitation to the maximum RF power. Several studies have concentrated on rectangular waveguide input couplers which are used in many light sources. Most of these studies neglect space charge assuming that the effect of space charge is simply to defocus the electron bunches. Modelling multipactor to saturation is of interest in determining the performance of waveguide under a range of conditions. Particle-in-cell modelling including space charge has been performed for 500 MHz half-height rectangular waveguide. Phase plots of electron trajectories can aid understanding the processes taking place in the multipactor. Results strongly suggest that the multipacting trajectories are strongly perturbed by space charge causing the electrons to transition from two-surface to single-surface trajectories as the multipactor approaches saturation.

Multipacting analysis in micro-pulse electron gun

“…The same as with Ref. [8], the transition that was caused by space charge effect from two-surface multipacting to single-surface multipacting in MPG is observed by analysis of simulation results. In Fig.…”

Recent advances in multipactor physics and mitigation

“…The effects of space charge on multipactor saturation have been extensively studied both analytically [2,44,95,137] and computationally [44,138]. In recent years, advanced computing capabilities and software (i.e., XPDP1, XOOPIC, CST, FEST3D, MEST, etc.)…”

Notes on the Variety of Multipactor Patterns

“…Many theoretical and experimental works on MP between parallel plates make this configuration a very convenient example for study and analyses. It should be mentioned that in real rectangular waveguides MP dynamic is more complicated due to the transverse variation of RF fields [8].…”