Breakdown characteristics in dielectric-confined microcavity discharge of plate electrodes

Abstract

Breakdown characteristics in dielectric confined microcavity discharge of plate-to-plate electrodes under DC voltage are investigated in this paper. Experimental and PIC-MCC simulated results show that the breakdown characteristic curve (the relation of breakdown voltage Vbr with the product pd of gas pressure and electrode gap, or the Vbr-pd curve) with microcavity effect will deviate from the traditional Paschen curve, and seed electron adsorption by the dielectric wall is considered as the deviation mechanism. Smaller microcavity height will enhance this deviation. Based on the deviation extent, there exist two critical microcavity heights hcr1 and hcr2 for the breakdown characteristic curve. When the cavity height h is larger than hcr1, the Vbr-pd curve conforms to Paschen’s Law due to the minor adsorbed electrons. When h < hcr1, the Vbr values in Vbr-pd curve begin to increase overall, compared to that in the Paschen curve. Specifically, when hcr2 < h < hcr1, the Vbr-1/h curve exhibits a positive linear relation; when h < hcr2, Vbr increases sharply with 1/h as a nonlinear relationship due to the massive adsorbed electrons. Additionally, the material type of dielectrics constructing the microcavity also has a significant impact on Vbr, which is related to the different electron adsorbility η of the various dielectric walls. For deeper insight, a “microcavity effect” analysis model was developed to discuss the modified Vbr-pd curve and give the explanation for the critical values of microcavity heights and the influence of dielectric material. Significant adsorption of charged particles (especially the seed electrons) by the dielectric wall will reduce the electron multiplication and further improve the breakdown voltage when the cavity height h is comparable to the product ηλe (the dielectric electron adsorbility and electron mean free path). On this basis, the modified breakdown criterion considering the microcavity effect was derived. The analytical expressions of the two critical height values hcr1 and hcr2 (hcr1 = 100ηλe, hcr2 = 10ηλe) and the linear relation of Vbr-1/h curve in hcr2 < h < hcr1 were presented quantitatively.

Characteristics of electric breakdown in repeated frequency pulse with microcavity effect

“…In figure 3, the breakdown time delay at smaller height h = 300 µm is much higher than that at h = 2000 µm, which is due to the obvious increase of statistical time delay by microcavity effect. At p = 800 Pa, there is nearly no microcavity effect when h is 2000 µm [29]. When h is 300 µm, a large number of charged and excited species inside the microcavity are adsorbed by the dielectric wall during afterglow period, and then the appearance rate Y of initial secondary electrons from the cathode will be decreased.…”

“…For breakdown with microcavity effect, Wang et al [29] and Guo et al [30] studied the discharge characteristics of a flat electrode microcavity structure driven by DC voltage and found that the breakdown voltage will increase with the reduction of microcavity height, which is considered as a result of the electron adsorption by the microcavity wall [29]. Liu et al [31] and Curcio et al [32] studied the breakdown of capillary discharge by simulation and experiment, and obtained similar results of electron adsorption.…”