On a dielectric-barrier and a microwave-cavity discharge in synchronized operation—the case of a helium/oxygen mixture

We have investigated the performance of a microwave-cavity discharge (MWD) operating in tandem with a fast rise-time pulsed dielectric-barrier discharge (DBD). The tandem discharge operated in a helium/oxygen mixture, where metastable molecular oxygen could be produced efficiently using MWD in proportionally large quantities (order of 20% of total oxygen number density). In this new arrangement, a DBD operating at high E/N provided a metastables-rich mixture, thereby modifying the discharge kinetics of the MWD, which operated in the E/N range centered around 10 Td. Both discharges operated in synchronized pulse-repetitive mode, which was tailored to maximize the oxygen metastable production efficiency. The system operated at pressures up to 350 Torr with an average power between 3 and 20 W.