Numerical analysis for suppression of charge growth using nested grooves in rectangular waveguides

Abstract

Multipactor mitigation is of relevance to microwave applications, and external magnetic fields, surface modifications, and materials engineering have previously been utilized for this purpose. In this contribution, geometric modifications made to rectangular waveguide surfaces in the form of nested grooves are investigated for the suppression of multipactor growth. A time-dependent kinetic scheme is used to simulate electron dynamics that folds in electron trapping at the nested groove structures, with inclusion of the electric field perturbations arising from the presence of various grooved geometries. The charge growth in the system is modeled based on an empirical approach that includes both energy and angular dependencies of secondary electron emission from all the different surfaces. A varying number of grooves, their widths, and their placement (either one sided or dual-sided) within the rectangular waveguide structure are included for a more complete analysis. The results demonstrate that nested grooves can lead to reductions in charge growth by over a factor of 280 when compared with a simple waveguide over the same time period. Furthermore, wider nested grooves are shown to have an advantage, with multiple aligned grooves across two parallel surfaces being especially useful at high external fields. Determining optimal combinations for an arbitrary field, operating frequency, and physical dimensions would require further work.

Particle traps constructed on the insulator of conductive slip rings for surface flashover mitigation under particle adhesion

“…Conversely, particle traps constructed in the center or near the anode exert less influence on the electric field at the CTJ, and because of the groove's hindering effect on the development of SEAs, particle traps positioned at these locations will enhance the flashover voltage of the dielectric. 28 According to the optimization results mentioned above, the most significant improvement in flashover voltage can be achieved by utilizing a single-groove particle trap positioned in the center between the electrodes. Building upon this finding, the structural parameters of the particle trap are further optimized as follows.…”

“…Consequently, SEA develops more readily at the bottom than at the sidewall. 28 In summary, for particle traps with relatively wide widths, there exists a critical depth that can restrict the SAC to a lower level, thereby increasing the flashover voltage. As illustrated in Fig.…”

Secondary roughness effect of surface microstructures on secondary electron emission and multipactor threshold for PTFE-filled and PI-filled single ridge waveguides

“…These methods have achieved success for the metals and inorganic ceramic dielectrics [29]. For metals, the effectiveness of groove structures in reducing SEY has been highlighted in recent literature [30][31][32][33]. In 2020, Ludwick et al reported a study on SEY modulation on microporous gold surfaces.…”

An alternative simulation approach for surface flashover in a vacuum using a 1D2V continuum and kinetic model

“…In a high degree of vacuum without an ionization source for discharge initiation, flashover begins from the cathode triple junction (CTJ) where electrode, insulator, and vacuum adjoin [14]. Due to the transient and nonequilibrium nature of the flashover process, numerical modeling provides valuable supplements to the experimental observations [15][16][17][18][19][20][21][22]. The particle-in-cell (PIC) method is a widely adopted numerical approach that is implemented in most, if not all, recent vacuum flashover simulation studies.…”