Optical characterization of atmospheric‐pressure plasma needle

Abstract

The atmospheric‐pressure plasma needle is a promising source that can be used efficiently for different industrial applications. A radio frequency (RF) (13.56 MHz) generator was used to generate a He–O2/Ar mixture plasma. The ground‐state oxygen atomic density [O] was calculated as a function of discharge parameters by “actinometry”. The Ar‐I (2p1 → 1s2) line at 750 nm and the O‐I (3P → 3S) line at 844 nm were used to estimate the [O] atomic density. The rotational temperature TR of He–O2/Ar mixture was measured from the rotational levels of the “first negative system” (FNS) by using the “Boltzmann plot”. The effect of discharge parameters on the atomic oxygen density [O] and the gas temperature was monitored. These results show that [O] density increases with RF power and O2 concentration, but decreases with the gas flow rate. Whereas the gas temperature increases with increase in the input RF power, it decreases with increase in the gas flow rate and O2 concentration in the mixture. Since the [O] atomic density contributes to plasma‐based biomedical applications, the proposed optimum conditions for plasma‐based decontamination of heat‐sensitive materials in the present study are 0.6% oxygen, 500 sccm flow rate, and 26 W RF power.