Investigation of grooved surface suppressing multipactor across HPM dielectric window

Abstract

Microwave breakdown phenomenon across dielectric window at the vacuum/dielectric interface limits the transmission of HPM and becomes a bottleneck of HPM technology development. Its avoidance or suppression is a major concern among researchers on HPM sources. Currently, the most effective approach is geometrical modification with the goal of altering the trajectories of electrons. In this paper, periodic rectangular grooves perpendicular to microwave electric field, are applied to improve the threshold of breakdown. To clarify the mechanism, the SEEA simulation model based on dynamic analysis and particle-in-cell (PIC) is built in this paper. The grooves change the electrons trajectories and eventually resonant multipactor condition may no longer be satisfied. The suppression effect is influenced by the grooves and each given width relates to an effective power range for suppression. Dielectric breakdown experiments under HPM of S-band at 2.86 GHz are conducted with the grooved dielectric window. The results of the experiment are consistent with theoretical analysis and simulation.

Modelling vacuum flashover mitigation with complex surface microstructure: mechanism and application

“…Chang et al [20] and Huo et al [21] studied the multipactor of the grooved surface with simulation, indicating that grooves can significantly enhance the surface strength of the dielectric. Similar studies have also been conducted by Song et al [22]. Surface roughness has been studied systematically by Guo et al [14], it is shown that both SEE and the surface charge accumulation are remarkably inhibited on a roughened surface.…”

Mechanism of vacuum flashover on surface roughness

“…In previous studies, a regular groove on the dielectric has been proved to be efficient in mitigating SEY [27,52,53]. In addition, it has been found that the groove parameter ought to be smaller than the critical parameter of collision distance λ min so that an avalanche cannot develop on the groove bottom and side walls [54]. The notion of λ min is also valid in our context.…”

Mechanism of F2/N2 fluorination mitigating vacuum flashover of polymers

“…In the former stage flashover voltage increases with surface roughness, while in the latter stage flashover voltage decreases with roughness. Such a notion of 'critical size', above which the surface microstructure fails to mitigate the surface multipactor, was also reported in a previous high power microwave test of a di electric window [43]. In addition, the influence of roughness was previously included in modelling secondary electron emission (SEE), where Vaughan introduced the 'smoothness factor' in his empirical formula to represent surface condition [44].…”