A dc non-thermal atmospheric-pressure plasma microjet

Abstract

A direct current (dc), non-thermal, atmospheric-pressure plasma microjet is generated with helium/oxygen gas mixture as working gas. The electrical property is characterized as a function of the oxygen concentration and show distinctive regions of operation. Side-on images of the jet were taken to analyze the mode of operation as well as the jet length. A self-pulsed mode is observed before the transition of the discharge to normal glow mode. Optical emission spectroscopy is employed from both end-on and side-on along the jet to analyze the reactive species generated in the plasma. Line emissions from atomic oxygen (at 777.4 nm) and helium (at 706.5 nm) were studied with respect to the oxygen volume percentage in the working gas, flow rate and discharge current. Optical emission intensities of Cu and OH are found to depend heavily on the oxygen concentration in the working gas. Ozone concentration measured in a semi-confined zone in front of the plasma jet is found to be from tens to ∼120 ppm. The results presented here demonstrate potential pathways for the adjustment and tuning of various plasma parameters such as reactive species selectivity and quantities or even ultraviolet emission intensities manipulation in an atmospheric-pressure non-thermal plasma source. The possibilities of fine tuning these plasma species allows for enhanced applications in health and medical related areas.

Nitric Oxide Generation with an Air Operated Non‐Thermal Plasma Jet and Associated Microbial Inactivation Mechanisms

“…A more effective production of a dc operated plasma jet, with a similar configuration, was recently observed also in the change in the intensity of emission spectra. [50] It has to be noted that the power provided with each pulse is much higher than the average power recorded in our experiments. With the pulsed or self-pulsing operation, fast rising voltage transients might change the electron distribution function toward higher energies.…”

“…Previous characterizations of a plasma that is generated from air at atmospheric pressure in a similar microhollow cathode discharge geometry found plasma temperatures of about 2 000 K for discharge currents of 4-13 mA when the gas was not flowing through the discharge channel. [33,50] However, for a flow rate exceeding 100 mL min À1 (at an operating current of 10 mA) does the plasma temperature already drop to values of less than 1 200 K and is decreasing further with increasing flow rate. [33] Overall, previous investigations allow for the reasonable conjecture that for gas flow rates on the order of liters per minute the plasma Figure 6.…”

Effects of Working Medium Gases on Emission Spectral and Temperature Characteristics of a Plasma Igniter

“…Zhu and Lopez used a mixture of He and O 2 as the working medium gas to conduct plasma microjet spectral characteristics experiments [15], and the results showed that the higher the concentration of the O 2 component in the mixture, the stronger the emission spectrum of OH and O 3 particles in the plasma jet. Wu et al obtained a nonequilibrium plasma via the rotating gliding arc discharge method [16] and studied the effect of the working medium gas on the plasma generated by the sliding arc discharge, in which N 2 and air were used separately as working gases for sliding arc discharge.…”

Studies of air, water, and ethanol vapor atmospheric pressure plasmas for antimicrobial applications

“…14 Extensive experimentation has been performed with plasmas that use room air and noble gases as starting gas materials. 15,16 Additional studies have been performed using cold plasma in order to create plasma-activated water that possesses antimicrobial properties. 10 In this study, the antimicrobial activity of air and mixtures of nonthermal (cold) plasmas using air with vaporized water and ethanol is investigated.…”