Self-pulsing 10{sup 4} A cm{sup -2} current density discharges in dielectric barrier Al/Al{sub 2}O{sub 3} microplasma devices

Excitation of Al/Al{sub 2}O{sub 3} microplasma devices with 50 {mu}s, 800 V pulses produces, in Ar/H{sub 2} gas mixtures at 600 Torr, {approx}6 A current pulses with a duration of {approx}30 ns. Corresponding to peak current and power densities of {approx}10{sup 4} A/cm{sup 2} and {approx}2.5 GW/cm{sup 3}, respectively, these pulses are generated in a 10 {mu}s burst in which the voltage self-pulses at a repetition frequency of {approx}3 MHz. Analysis of the H{sub {alpha}}, H{sub {beta}}, and Ar II emission line profiles yields a plasma density of {approx}10{sup 17} cm{sup -3}, and the emission of O IV ions suggests the presence of energetic electrons. Images of the microplasma indicate that the plasma is initiated by surface flashover and extends {approx}200 {mu}m outside the microcavity.