Characteristics of impurity-dependent breakdown in helium dielectric barrier discharge jets

Summary form only given. Multiple current pulses during breakdown (or so-called pseudoglow discharge) in floating-electrode dielectric barrier discharge jets (DBD jets) were studied in this work. Industrial grade helium (purity 99.995 %) and the helium with impurity were employed for the DBD jet generation. Preliminary works used methyl methacrylate (MMA, ~1800 ppm) as the added impurity. Based on the electrical characteristics, both the jets show the characteristics of multiple current pulses during breakdown but contained different numbers, widths, and sequencing of current pulses, as shown in Fig. 1. In the pure helium DBD jet, several relatively small pulses form a single broad current pulse per half-cycle, while with MMA several more widely separated current pulses occur. It was also seen that the number of the current pulses in the helium and helium/MMA DBD jets increases with the rising power. These current pulses were correlated with results from time resolved intensified charge-coupled device (ICCD) imaging and photomultiplier tube (PMT) traces of the discharge. It was observed that each broadened current pulse in both DBD jets mainly consists of a leading ionization wave (or plasma bullet) and several successive breakdowns. In helium/MMA with increasing power initially there are multiple ionization waves per half cycle though as the time between current pulses decreases the wave propagation becomes less noticeable. With only helium the time between current pulses is so short that only one leading wave is ever observed.