Penetration of ionization wave through dielectric microhole in atmospheric pulsed discharges

Microstructure-enhanced discharges are critical for achieving higher plasma electron density and energy, offering significant potential in advanced plasma applications. A two-dimensional fluid model of pulsed dielectric barrier discharge was developed in atmospheric helium with a dielectric microhole. Two distinct high-electron-density regions, the T-region and L-region, were identified, driven, respectively, by transverse and longitudinal electric fields as the ionization wave traversed the microhole. The axisymmetric T-region is approached and squeezed as the radius decreases, in which the discharge intensity and electron density are enhanced. Based on the electron reaction source item, a virtual electrode is proposed in the dielectric microhole, which segregates the T- and L-regions. The width of the virtual electrode decreases with the microhole radius, and the virtual electrode extinguishes with the discharge ignition in the lower chamber and the formation of ionization wave in the dielectric microhole. These findings offer insights into plasma behavior in microstructures for advanced applications.