Systematic diagnostics of the electrical, optical, and physicochemical characteristics of low-temperature atmospheric-pressure helium plasma sources

Abstract

The performance characteristics of two plasma sources, based on different types of discharge, were assessed. Three primary aspects of these sources were examined. These were electrical parameters (voltage and current flowing through a target), plasma parameters (gas temperature and electron density, determined using optical emission spectroscopy), and levels of gas-phase oxygen atoms (measured by vacuum ultraviolet absorption spectroscopy) and liquid-phase ▪OH radicals (generated by plasma treatment of water and detected using an electron spin resonance spin-trapping technique). As a result, there were few significant differences such as electron density, oxygen atom density, and gas temperature between the two plasma sources. However, the time-averaged electrical currents flowing to the target and the amount of liquid-phase ▪OH radicals showed a large difference, especially when the plume made contact with the target. Thus, many points of similarity but some differences in the two devices were found by the benchmarking study. These shall contribute to our understanding of the mechanisms for each consequence in medical applications.