Comparison on the Absolute Concentrations of Hydroxyl and Atomic Oxygen Generated by Five Different Nonequilibrium Atmospheric-Pressure Plasma Jets

Nonequilibrium atmospheric pressure plasma jets (N-APPJs) generate near or at room temperature plasmas in open space, which is attractive for various applications such as plasma medicine. Because of this advantage, different types of N-APPJs have been reported. Reactive species, such as hydroxyl (OH) and atomic oxygen (O), generated by N-APPJs, are believed to play important roles for many applications. However, there is no report on the comparison of the reactive species concentrations generated by different types of N-APPJs. In this paper, the absolute concentrations of OH and O generated by five different configurations of widely used N-APPJs are compared. For this initial study, all five N-APPJS are driven by the same pulsed dc power supply. Besides, the effects of different operating parameters, including the amplitude of the applied voltage, frequency, the content of the working gas, and the gas flow rate, on their concentrations are investigated. It is found that the OH and O concentrations of the five N-APPJs could have up to one order and five-folder difference, respectively. On the other hand, for all five devices, their peak O concentrations are about two orders higher than their peak OH concentrations. Finally, from the energy point of view, the reactive species generation efficiency of these devices are discussed and future work is proposed.