Numerical simulations of high power microwave dielectric interface breakdown involving outgassing

Abstract

With the development of high power microwave (HPM) technology, the power and pulse duration of the HPM source increase substantially, the breakdown of the dielectric window of the HPM source feed has been becoming the major factor of limiting the transmission and radiation of HPM. This paper presents an electrostatic particle-in-cell and Monte Carlo collisions method for simulating the breakdown on HPM dielectric surface and establishes a physical model of HPM dielectric surface breakdown involving outgassing. The breakdown process including the main physical mechanisms, such as the field emission, multipactor, outgassing, and collision of gas ionization, is simulated. The influence of outgassing on the dielectric window breakdown is studied by simulating the breakdown with different outgassing speeds. The similarity between the dc and HPM dielectric surface breakdown is discussed.

Suppression of multipactor discharge on a dielectric surface by an external magnetic field

“…4 When the multipactor is cut off in the half time of HPM transmission, the formation time of the gas layer will increase to two times. Because the number of the multipactor electrons is linear to the strength of microwave electric field, the breakdown threshold of the HPM power will increase to four times in an external magnetic field with a certain value.…”

“…[1][2][3] In the process of the breakdown, the multipactor plays a key role, and it decides the velocity of outgassing and the formation of the gas layer which is the necessary condition of final gas breakdown. 4 So the suppression of multipactor can delay or avoid the dielectric surface breakdown, and it has been a major concern among researchers on HPM sources.…”

Tracking multiple generation and suppression of secondary electrons on periodic triangular surface

“…[12][13][14][15] Secondary electron multipactor causes the local gas desorbed, triggers flashover, and leads to the final vacuum window breakdown. [16][17][18][19][20] The secondary emission yield can be referenced from the formulation in 21,22 …”

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

“…Following the paper of Ref. 13, the electron stimulated outgassing model developed by Wang et al is adopted to take into account the effect of desorbed gas layer. To focus on the essential physics and avoid the complex of desorbed gas, argon is assumed as the actual desorbed gas.…”