Electrical, thermal and optical diagnostics of an atmospheric Plasma jet system (original) (raw)
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Investigation on Parameters of Atmospheric Pressure Plasma Jet by Electrical and Optical Methods
2020
The atmospheric pressure plasma jet works under atmospheric pressure condition, has been developed for surface treatment and biomedical applications. The produced jet has been characterized by electrical and optical methods. To characterize cold atmospheric argon plasma discharge, its electron density, and electron energy (temperature) at various conditions have been estimated by using different techniques such as power balance, stark broadening, and intensity ratio methods respectively. Atmospheric pressure plasma jet (APPJ) has drawn much attention all over the world due to its applications in material processing, biomedical material processing, and thin film deposition. APPJ has been produced, using a high voltage and high frequency power supply (0-20 kV) and an operating frequency of 20 kHz. Results showed that the electron density was of the order of 10 14 cm -3 and 10 16 cm -3 as determined by power balance, intensity ratio, and stark broadening methods respectively while elec...
Physics of Plasmas, 2013
Low-temperature, high-pressure plasma jets have an extensive use in medical and biological applications. Much work has been devoted to study these applications while comparatively fewer studies appear to be directed to the discharge itself. In this work, in order to better understand the kind of electrical discharge and the plasma states existing in those devices, a study of the electrical characteristics of a typical plasma jet, operated at atmospheric pressure, using either air or argon, is reported. It is found that the experimentally determined electrical characteristics are consistent with the model of a thermal arc discharge, with a highly collisional cathode sheet. The only exception is the case of argon at the smallest electrode separation studied, around 1 mm in which case the discharge is better modeled as either a non-thermal arc or a high-pressure glow. Also, variations of the electrical behavior at different gas flow rates are interpreted, consistently with the arc model, in terms of the development of fluid turbulence in the external jet. V
Diagnostics of Atmospheric Pressure Air Plasmas
Atmospheric pressure air plasmas are often thought to be in Local Thermodynamics Equilibrium (LTE) owing to fast interspecies collisional exchanges at high pressure. As will be seen here, this assumption cannot be relied upon, particularly with respect to optical diagnostics. Large velocity gradients in flowing plasmas and/or elevated electron temperatures created by electrical discharges can result in large departures from chemical and thermal equilibrium. Diagnostic techniques based on optical emission spectroscopy (OES) and Cavity Ring-Down Spectroscopy (CRDS) have been developed and applied at Stanford University to the investigation of atmospheric pressure plasmas under conditions ranging from thermal and chemical equilibrium to thermochemical nonequilibrium. This article presents a review of selected temperature and species concentration measurement techniques useful for the study of air and nitrogen plasmas.
Generation of Active Species in a Large Atmospheric-Pressure Plasma Jet
IEEE Transactions on Plasma Science, 2000
Low-temperature atmospheric-pressure plasma jets (APPJs) are being increasingly used in surface activation, cleaning, wound care, and sterilization applications. The development of successful applications using these systems depends on the ability to tailor the active species generated in the plasma jets to match the treatment requirements. This paper presents an investigation of the effect of sinusoidal drive frequency (20-140 kHz), on a helium discharge formed using an APPJ. The discharge was formed in a large-orifice 16-mm-diameter quartz tube with a treatment area of ≈ 2 cm 2 at the nozzle exit. Optical, polychromic emission, and thermographic imaging data were correlated with electrical measurements. These measurements indicated that the coupling efficiency was frequency dependent. As a result of differences in coupling efficiency, variations in active species (N 2 , N + 2 , O, and NO) present in the discharge were observed. The concentration of active species was also dependent on the distance from the powered electrodes. As well as altering the concentration of active species in the discharge, changes in frequency resulted in higher discharge temperatures (25 • C at 20 kHz to 40 • C at 80 kHz). The temperature was measured on the quartz tube, and steady state was reached after 120 s. This paper presents a detailed analysis of the frequency/distance dependence on the active species in the discharge. This dependence makes it possible to control the active species present at the plasma jet orifice by tailoring the frequency and tube length.
Direct current plasma jet at atmospheric pressure operating in nitrogen and air
Journal of Applied Physics, 2013
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High voltage pulsed, cold atmospheric plasma jets: Physical characteristics for various geometries
2008 IEEE 35th International Conference on Plasma Science, 2008
Three types of cold atmospheric plasma jet generators are described. The plasma jet generators are supplied with repetitive high voltage pulses: maximum 20 kV amplitude, hundreds of ns width, up to 100 pulses per second. The obtained cold atmospheric plasma jets have lengths of up to 50 mm. For the first time, the plasma jet current has been measured along the plasma jet length.
Plasma Sources Science and Technology, 2014
An extensive electrical study was performed on a coaxial geometry atmospheric pressure plasma jet source in helium, driven by 30 kHz sine voltage. Two modes of operation were observed, a highly reproducible low-power mode that features the emission of one plasma bullet per voltage period and an erratic high-power mode in which micro-discharges appear around the grounded electrode. The minimum of power transfer efficiency corresponds to the transition between the two modes. Effective capacitance was identified as a varying property influenced by the discharge and the dissipated power. The charge carried by plasma bullets was found to be a small fraction of charge produced in the source irrespective of input power and configuration of the grounded electrode. The biggest part of the produced charge stays localized in the plasma source and below the grounded electrode, in the range 1.2-3.3 nC for ground length of 3-8 mm.
Three distinct modes in a cold atmospheric pressure plasma jet
Journal of Physics D: Applied Physics, 2010
Cold atmospheric pressure helium plasma jets are increasingly used in many processing applications, due to a distinct combination of their inherent plasma stability with excellent reaction chemistry often enhanced downstream. Despite their widespread usage, it remains largely unknown whether cold atmospheric plasma jets maintain similar characteristics from breakdown to arcing or whether they possess different operating modes. In addition to their known ability to produce a fast moving train of discrete luminous clusters along the jet length, commonly known as plasma bullets, this paper reports evidence of two additional modes of operation, namely a chaotic mode and a continuous mode in an atmospheric helium plasma jet. Through detailed electrical and optical characterisation, it is shown that immediately following breakdown the plasma jet operates in a deterministic chaotic mode. With increasing input power, the discharge becomes periodic and the jet plasma is found to produce at least one strong plasma bullet every cycle of the applied voltage. Further increase in input power eventually leads to the continuous mode in which excited species are seen to remain within the inter-electrode space throughout the entire cycle of the applied voltage.
2010
A cross-flow atmospheric plasma jet with distilled water or analyte solution nebulization has been investigated. The plasma gas flows perpendicularly to the RF powered electrode (11.21 MHz) and a grounded electrode was added for plasma stabilization. The working parameters of the plasma generator can be controlled in order to maximize either the plasma power (75 W) or the voltage on the RF powered electrode (plasma power, 40 W). The plasma gas, pure argon (0.4 l min −1) or a mixture of argon (0.3-0.4 l min −1) and helium (0-0.2 l min −1), was also used for liquid nebulization. Optical emission of the plasma, collected in the normal viewing mode, was used for plasma diagnostics and for evaluating its excitation capabilities. The influence of helium content in the mixed-gas plasma on the plasma characteristics and on the emission axial profiles of the plasma gas constituents and of the analytes originate from the wet aerosol was studied. The addition of helium to the argon plasma, generally determines decreases in the emission of the plasma gas constituents (with the exception of molecular nitrogen), in the rotational temperature and in the electron number density and increases in the excitation temperatures and in the emission of easily excitable analytes. Based on the determined electron number densities, it was concluded that in the plasma zone which presents interest from analytical point of view the plasma is not very far from the partial thermodynamic equilibrium. In function of the helium content in the plasma gas and of the axial distance from the powered electrode the excitation temperatures are in the range of 2420-3340 K for argon, 2500-5450 K for oxygen and 900-2610 K for ionic calcium and the electron number densities are in the range of 1.2 10 12-1.25 10 13 cm −3. Some elements with excitation energy lower than 6 eV were excited in the plasma. The plasma excitation capability depends on the working conditions of the plasma generator (maximum power or maximum voltage on the RF powered electrode) and on the helium content in the mixed-gas plasma. The estimated detection limits for the studied elements (Na, Li, K, Ca, Cu, Ag, Cd, Hg and Zn) are in the range of 7 ng ml −1 to 28 μg ml −1 .
Plasma Sources Science and Technology, 2011
An atmospheric pressure plasma jet generated in Ar with water vapor is investigated. It is shown that an increase in the water content results in a decrease in the input power and asymmetry of the current waveform on positive and negative half-periods of the applied voltage. Space-resolved spectroscopy with a resolution of 1 mm and an imaging technique are applied for the characterization of the afterglow and investigation of the influence of water content on plasma properties. The rotational temperature of the jet is determined by simulation of the OH radical emission spectrum, transition A 2 + (v = 0) → X 2 (v = 0). It is revealed that the temperature of the discharge increases from 450 K (Ar) up to 850 K with an increase in the water content up to 7600 ppm. Generation of the discharge in mixtures of argon with water vapor at a concentration of 350 ppm results in a maximal yield of OH radicals that can be useful in plasma jet applications. Preliminary tests of polypropylene surface modification are carried out in order to estimate the influence of water content on the results of treatment.