Electromagnetic particle-in-cell verification of improving high-power microwave window breakdown thresholds by resonant magnetic field

Abstract

High-power microwave driven vacuum dielectric window breakdown is found to be suppressed by external magnetic field with gyrofrequency Ω = eB/m close to angular frequency ω of rf electric field. This letter gives a particle-in-cell demonstration of the increasing of breakdown thresholds by such magnetic field. It is found that magnetic field with Ω ∼ ω mitigates the multipactor effect. Its saturation process occurs at upper boundary of the susceptibility diagram instead of the lower one. This decreases the dc electric field built on dielectric surface. The electron-dielectric interaction rate is lowered, especially in the half rf period with Erf × B force pointing out of the dielectric surface. The resulting flashover time delay is prolonged. Thereby, the power handling capability of the dielectric window is enhanced.

Estimation of surface flashover threshold in vacuum: from multipactor to discharge plasma

“…Previous study found that vacuum flashover varies with insulator length in form of V flashover = kd α where α is smaller than 1 [34][35][36]. Such conclusion does not contradict with equation (24) if the implicit relation between P crit and d is considered. To determine the critical pressure, one may simplify the gas breakdown and calculate the first Townsend coefficient as a function of pressure and applied electric field.…”

“…Theoretical results are compared with our PIC simulation code in figure 3. PIC method is widely used in surface flashover under DC or radio frequency condition [23,24]. Validation of implemented PIC code can be found in our previous studies [22,25,26].…”

“…Value of k s is taken as 0 for rough case, 1 for normal case, and greater for ideal surface. Part of SEY curve for quartz is shown in figure 7 where higher k s leads to greater A 1 , and therefore more robust withstand strength according to equation (24).…”

Comparative analysis of single-surface multipactor discharges at different microwave frequencies

“…12) The temporal and spatial evolution characteristics of multipactor discharges were extensively investigated by a particle-in-cell method. [13][14][15] The energy of an electron hitting the dielectric surface in a vacuum and at different pressures is obtained by solving the momentum conservation equation of the electron, in order to discuss the effect of desorption gas on dielectric surface discharge. 16) In recent years, some new electron multipactor theories and suppression methods of the multipactor have been reported.…”

A hybrid mode of one- and two-surface multipactor on grooved dielectric surface

“…The former often occurs on the RF window surface or insulator surface, requires an applied electric field parallel to the dielectric surface and a direct current (DC) electric field from the charging of the dielectric surface, and has been profoundly investigated experimentally, theoretically, and numerically. [8][9][10][11][12][13][14][15][16][17][18][19][20][21] The latter requires a resonant RF electric field perpendicular to the plate surface, and often occurs on the waveguide or metal gap. [1,22] Despite the extremely similar physical process, they are always thought to occur on different devices solely and are studied by researchers from different fields separately.…”