Characteristics Of Plasma Jet Research Articles

Influence of duty cycle on the physicochemical characteristics of an AC-driven argon plasma jet and its impact on hydrogen peroxide production and cell viability

This paper investigates how the duty cycle influences the production of hydrogen peroxide (H2O2) in an alternating current (AC)-driven plasma jet. H2O2 is a major reactive oxygen species produced by plasma jets in medicine and is a biological important molecule because it can intervene in cellular signaling processes important for disease treatment. In this study, duty cycles were varied from 9% to 72%, which correlated with an increase in the plasma’s dissipated power and UV photon energy density, and consequently an increase in the production of high energy plasma components important for producing H2O2 through electron collision and UV photolysis reactions. Cell media treated with the plasma jet at higher duty cycles correlated with a decrease in the viability of HaCaT keratinocyte skin cells. The AC-driven plasma jets were shown to be operated optimally at a biocompatible gas temperature of below 40 °C whilst still maintaining efficiency in H2O2 production. Overall, the data presented in this study might find use for the future of optimization of the electrical properties of AC-driven plasma jets in plasma medicine.

Development of a pulse modulated sub-radio frequency power supply for atmospheric pressure plasma devices.

The effect of pulse-modulated sub-RF range (100 kHz-1MHz) excitation on atmospheric pressure argon plasma jet characteristics is studied. For this, a suitable power supply is developed, offering a sub-µs rise time with control of different parameters, such as voltage amplitude, pulse modulation frequency in the range of 1-30kHz, and an oscillation frequency of ∼520kHz, which can affect the plasma behavior. Plasma characteristics, such as reactive species generation, ionic composition, plasma plume length, and gas temperature, are evaluated qualitatively and quantitatively by employing diagnostics such as optical emission spectroscopy, molecular beam mass spectrometry, and optical imaging. Experimental observations indicate that the gas temperature of the plasma jet and plume length increase with the applied voltage for all pulse modulation frequencies, with a maximum value of ∼(325 ± 2K) and a maximum length of ∼(23 ± 3mm), respectively, at 30kHz and 9 kVpp. The emission intensities of OH• and O• lines show an incremental behavior with the applied voltage across all pulse modulation frequencies. The relative yield of different positive (OH+, O+, etc.) and negative (OH-, O-, etc.) ions also increases with the applied voltage for all pulse modulation frequencies with maximum values of ∼(7.6%, 9.9%) and (3.9%, 9.4%), respectively; these are relatively close to RF excited ionic concentrations reported previously. Attaining a high plasma length and species yield signify the features of both kHz and RF atmospheric plasmas. This study offers significant insights and flexibility into exploring the impact of different RF frequency regimes on plasma characteristics.

Study on the rock-breaking characteristics of high-energy pulsed plasma jet for granite

Plasma jet rock-breaking technology, characterized by its high rock-breaking efficiency, low specific energy, and absence of mechanical wear, is one of the most promising methods for efficiently fracturing hard rock formations such as hot dry rock (HDR). This study designed a novel high-energy pulsed plasma power supply and pulsed gas supply system to achieve rock fracturing through the instantaneous high-temperature and thermal stress impact of the high-energy pulsed plasma jet on the rock surface. This paper conducted comparative experiments with a traditional constant plasma jet. The impact of crucial electrical parameters (peak current, valley current, frequency, and duty cycle) and rock initial temperature on the damage and fracturing patterns of granite was extensively investigated. Comprehensive evaluation criteria, including removal mass, diameter, depth, rate of penetration, and specific energy, were employed to study the effects meticulously. The results indicate that the pulsed plasma jet significantly enhances energy utilization, effectively reducing the occurrence of thermal melting. The specific energy decreased significantly by 54.74%, while the rate of penetration increased by 17.81%. Additionally, electrode wear was reduced by 50.06%, extending the lifespan of the plasma bit. Parametric analysis revealed that the peak current is the primary factor influencing the rock-breaking performance and efficiency. The valley current has minimal impact on hole morphology but significantly affects specific energy. Frequency and duty cycle can be adjusted to optimize the single-pulse energy, achieving the best specific energy and efficiency. Additionally, the rock temperature has a great influence on the breaking effect. The fracturing characteristics of granite were also analyzed from a microscopic level. Based on the experimental results, recommended parameters of pulsed plasma jet are provided for breaking granite. These findings offer guidance for high-energy pulsed plasma jet drilling of HDR.

Online Diagnostic Method and System Design of Arc Plasma Jet Characteristics Based on Wavelet Transform and Linear Regression Theory

Online Diagnostic Method and System Design of Arc Plasma Jet Characteristics Based on Wavelet Transform and Linear Regression Theory

Analysis of the strength property of capillary plasma generator

Plasma generator is a key component of electrothermal chemical gun. Its function is to produce plasma under the action of high pulse current and enhance the combustion characteristics of the propellant, thus improving the launch efficiency and muzzle velocity. The structural properties of the plasma generator are related to its discharge characteristics, internal pressure, and plasma jet characteristics, etc. This paper studies the strength property of capillary plasma generator under working conditions, and provides a reference for the structural design of the plasma generator.

Study of annular coaxial powder feeding effect on the characteristics of laminar plasma jet and atmospheric cluster deposition

In this paper, by means of numerical simulation and experimental analysis, the performance of the engulfment based annular coaxial powder feeding method and the particle behaviors were studied in the laminar plasma spraying process. First, numerical simulation methods are used to analyze the flow state of the laminar plasma jet and its interaction with the powder particles. Then, the laminar plasma spray was applied to deposit coatings based on the annular coaxial powder feeding method, and the performance of this method was evaluated by observing the coatings. The numerical simulation results show that the powder particles can be fed into the laminar plasma jet without affecting the flow state of the plasma jet, and can be sufficiently heated. The experimental results are consistent with the numerical simulation results. The surface morphologies of the coatings indicates that vapor phase deposition and liquid phase deposition occur simultaneously during the spraying process, and the laminar plasma spray - physical vapor deposition process has the potential to be applied in atmospheric environments.

Characteristics of Cold Atmospheric Plasma Jet when Excited by Sinusoidal and Positive Pulse Voltages for Medical Applications

Low-temperature plasma jets at atmospheric pressure generated by sinusoidal and positive pulsed voltages interact differently with the treated surface. In the experiment and in numerical simulations, we compare the operating modes of helium plasma jets for these types of operating voltages. The discharge current on the treated surface over time and the surface heating are studied for different discharge parameters acceptable for anticancer therapy. The intensity of the emission spectrum is analyzed to improve the effectiveness of the plasma jet. Surface heating is controlled in order to meet the safety conditions of plasma exposure to biological objects. For the case of pulsed voltage the effect of voltage pulse duration on the intensity of plasma-surface interaction is discussed. The results on cancer cells A549 and MCF-7 demonstrate the high efficiency of the cold plasma jet generated at found optimal modes.

Quasi-direct numerical simulations of the flow characteristics of a thermal plasma reactor with counterflow jet

Three-dimensional quasi-direct numerical simulations have been performed to investigate a thermal plasma reactor with a counterflow jet. The effects of the momentum flux ratio and distance between the counterflow jet and the thermal plasma jet on the flow characteristics are addressed. The numerical results show that the dimensionless location of the stagnation layer is significantly affected by the momentum flux ratio, but it is not dependent on the distance. Specifically, the stagnation layer is closer to the plasma torch outlet with the increase of the momentum flux ratio. Furthermore, the flow regimes of the stagnation layer and the flow characteristics of the thermal plasma jet are closely related to the momentum flux ratio. The characteristic frequencies associated with the different regimes are identified. The deflecting oscillation flow regimes are found when the momentum flux ratio is low, which provokes axial velocity fluctuations inside the thermal plasma jet. By contrast, for cases with a high momentum flux ratio, flapping flow regimes are distinguished. The thermal plasma jets are very stable and the axial velocity fluctuations mainly exist in the stagnation layer.

Numerical study of a plasma jet for plasma-assisted laser cutting

Laser fusion cutting commonly applies a high-pressurized nitrogen gas jet to blow the molten material out of the cut kerf. However, theoretical considerations suggest that the use of a plasma jet may offer some advantages over this conventional approach. In this preliminary investigation, the characteristics of a non-transferred plasma jet for the application as auxiliary gas in laser beam cutting are analyzed using numerical CFD simulation. Based on this study, a first prototype of a plasma jet generator was manufactured and used in initial cutting experiments on 6 mm thick AISI 304 stainless steel. Two different cooling concepts for the plasma torch were considered and investigated in practice. Suitable values for the nozzle exit diameter, the distance between the electrodes of the plasma torch, the auxiliary gas flow rate and the electric current were identified both model-based and experimentally. The achieved cutting performance is considered a proof-of-principle of the suggested approach of a plasma-assisted laser beam cutting process.

A study of the behaviorof the discharge parameters and their effects on the mechanical design of an electrothermal gun

This paper gives an overview of finding the discharge parameters equations and their effects on the design criteria of ETA as well as the realized design solutions. The aim of this study is to obtain information about the discharge parameters in an electrothermal gun by extending the previous models of different researches and analyze their equations. Different physical processes in confined high-pressure discharge analyzed. For a given discharge, ablation rate and plasma pressure,the tube length is limited. An analytical model is developed for confined high-pressure discharges operating in a quasi-steady state, in which the resulting plasma jet characteristics are steady at hydrodynamic timescales. This model allows the calculation of all the discharge parameters, such as ablation rate; plasma temperature; plasma sound velocity; density; current density and pressure, as a function of the "slowly varying" current and the tube dimensions. Good agreement for the results obtained between the theoreticalmodel, which is built, and the experimental results for global research.

Efficient hydrophilicity improvement of titanium surface by plasma jet in micro-hollow cathode discharge geometry

Surface hydrophilicity improvement of titanium (Ti) is of great significance for the applications of the important biomaterial. In this study, efficient hydrophilicity on the Ti surface is improved by an air plasma jet generated by a micro-hollow cathode discharge (MHCD) geometry. Elementary discharge aspects of the plasma jet and surface characteristics of the Ti surface are investigated by varying dissipated power (P d). The results show that the plasma jet can operate in a pulsed mode or a continuous mode, depending on P d. The plume length increases with P d and air flow rate increasing. By optical emission spectroscopy, plasma parameters as a function of P d are investigated. After plasma treatment, water contact angel (WCA) of the Ti sample decreases to a minimum value of 15° with P d increasing. In addition, the surface topography, roughness, and content of chemical composition are investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM), and x-ray photoelectron spectroscopy (XPS) with P d increasing. The results show that Ti–O bond and O–H group on the Ti surface are beneficial to the improvement of the hydrophilicity of Ti surface.

Contrasting the characteristics of atmospheric pressure plasma jets operated with single and double dielectric material: physicochemical characteristics and application to bacterial killing

This study reports an experimental comparison of two types of atmospheric pressure plasma jets in terms of their fundamental plasma characteristics and efficacy in bacterial sterilization. The plasma jets are fabricated by inserting a high voltage electrode inside a one-end closed (double DBD plasma jet) or both ends open (single DBD plasma jet) quartz tubes which are further enclosed inside a second quartz tube containing a ground electrode. Both plasma jets are operated in contact with water surface by using a unipolar pulsed DC power supply with helium as the working gas. Results from electrical and time-resolved imaging show that the single DBD configuration induces 3–4 times higher accumulation of charges onto the water surface with significantly faster propagation of plasma bullets. These results are accompanied by the higher discharge intensity as well as stronger emissions from short-lived reactive species which were analyzed through optical emission spectroscopy at the plasma-water interface. The rotational temperature for the single DBD configuration was observed to be higher making it unsafe for direct treatments of sensitive biological targets. These characteristics of the single DBD configuration result in the production of more than two times higher concentration of H2O2 in plasma activated water. Shielding of the HV electrode reduces the plasma potential which in turn reduces the electric field & electron energy at the plasma-water interface. The reduced electric field for the double DBD configuration was lower by ≈463 Td than the single DBD configuration. The bactericidal efficacy of the two configurations of the plasma jets were tested against Escherichia coli, a well studied Gram-negative bacterium that can be commensal and pathogenic in human body. Our results demonstrate that although single DBD plasma jet result in stronger antibacterial effects, the double DBD configuration could be safer.

Effects of gas inlet orientation on discharge characteristics of coaxial dual-channel cross-field atmospheric plasma jet

In this paper, the effect of the gas inlet orientation on the discharge characteristics of the coaxial dual-channel cross-field plasma jet is investigated. A working gas helium is separately flowed into the annular space between the hollow needle tube and the quartz tube (called Q-Jet), as well as the hollow needle tube (called N-Jet). With the same discharge parameters, the results show that the radial and axial dimensions of Q-Jet plasma jet are larger than that of N-Jet. Compared with the latter, the discharge current amplitude of the former increases by about 3.8-fold, the net charge transferred increases by about 8.8-fold, and the variety and density of reactive species produced are remarkably increased. For Q-Jet, the 706-nm spectral band is distributed inside and outside the quartz tube, while the 391-nm spectral band is mainly distributed outside the quartz tube, and the plasma jet forms a conical luminous pattern in the quartz tube during the positive half cycle of the voltage, due to the influence of helium viscosity. For N-Jet, 706- and 391-nm spectral bands are only just distributed in the axis of the quartz tube, and the charges left by the first discharge in the axial position of the quartz tube remarkably amplify the intensity of the second discharge in the positive half cycle.

The influence of electrodes thicknesses on the characteristics of a helium plasma jet

An atmospheric plasma jet reactor (PJR) was designed using two outer disc-like copper plats placed around a quartz tube. The effects of the electrodes’ thicknesses and their placement on the plasma jet length created in helium and its electrical characteristics were investigated. Measurements of the plasma jet length were carried out for different applied voltages and different gas flow rates. The electrical characteristics (such as discharge current and power consumption) of the plasma jet obtained using a high voltage generator delivering a sin-wave signal varying from 13kVp-p to 17kVp-p at a resonance frequency of 5.5kHz, were measured/calculated. The best results (long plasma plume and intense plasma) were obtained with a reactor equipped with a thicker upper electrode and a thinner lower electrode. Using this configuration, a plasma plume 55mm long was reached at 17kVp-p and 7slm of helium.

DC erosion jets for the production of composite graphene particles

We studied the synthesis of composite Cu/graphene nanoparticles using the radiative characteristics of copper-containing plasma jets of a helium/hydrocarbon mixture, flowing from the nozzle of the output copper electrode of a DC plasmatron. A mixture of propane and butane was used as the hydrocarbon source. To determine the conditions for nanoparticle formation during the conversion of hydrocarbons in erosive jets, the concentration of copper was estimated by analyzing the optical emission spectra of Cu I lines observed in the spectrum. We found that the maximum saturation of graphene by copper (0.03 mass %) is reached at the copper concentration in plasma [Cu] = Nabs ≈ 3 × 1013 cm−3, which is sufficient to form a chemical bond of copper with sp2 carbon in a nanoparticle.

Experimental study of the heat transfer characteristics of plasma jets in circular tubes under applied magnetic fields with different orientations

Numerical studies have demonstrated that heat transfer between magnetogasdynamic flow in a tube with the tube wall can be regulated via the application of magnetic fields. However, the development of corresponding thermal energy control applications is limited owing to a lack of effective experimental verification of these numerical findings. The present study addresses this issue by developing an experimental system for studying the effects of applied magnetic fields lying parallel and perpendicular to the direction of flow on the convective heat transfer of plasma jets generated by a dielectric barrier discharge (DBD) reactor in circular tubes, where the heat transfer parameters within the tube are calculated according to temperature measurements on the outer wall of the tube. The results demonstrate that both types of applied magnetic fields tend to suppress heat transfer between the plasma jet and the tube walls, where the effect of the perpendicular electromagnetic field on the heat transfer is anisotropic, while that of the parallel electromagnetic field is isotropic. In addition, the magnetic field intensity, the excitation voltage of the DBD reactor, and the airflow velocity at the inlet are all demonstrated to have regulatory effects on the observed heat transfer between the plasma jet and tube walls. These results lend considerable substance to the findings of numerical studies indicating that the geometrical parameters and intensities of magnetic fields must be coordinated with the specific requirements and flow parameters inherent in practical applications.

Spectral diagnosis of atmospheric pressure AC argon plasma jet at constant power

In the application of atmospheric pressure plasma jet, because the frequency of AC power supply is limited in the kHz range, the research on the influence of power supply electrical parameters on discharge is basically aimed at the variation of plasma jet characteristics with a single driving electrical parameter ( such as voltage and frequency). However, the discharge power usually changes with a single electrical parameter changing, which can undoubtedly affect the discharge performances including the plasma physical parameters and generated reactive species, resulting in the failure to reflect the influence of the single driving parameter on the discharge. In this study, an atmospheric pressure argon plasma jet is driven by a home-made AC power supply with adjustable pulse modulated duty cycle. And combining the diagnosis of the optical emission spectrum and the optical absorption spectrum, the influences of the voltage, frequency and pulse modulated duty cycle parameters on the gas temperature <i>T</i><sub>g</sub>, electron excitation temperature <i>T</i><sub>exc</sub>, electron density <i>n</i><sub>e</sub>, and OH radical particle number density of the plasma jet are studied under a constant discharge power of 2 W. The results show that at the constant power, the electron density n<sub>e</sub> does not change with the variation of electrical parameters as the linkage change of electrical parameters will offset the influence of a single parameter on the electron density, while the gas temperature <i>T</i><sub>g</sub>, electron excitation temperature <i>T</i><sub>exc</sub>, and OH radical particle density are most affected by the pulse modulated duty cycle, followed by driving voltage, and the frequency effect is the smallest. Under the constant power, as the frequency decreases, the voltage will increase, and also the gas temperature <i>T</i><sub>g</sub>, electron excitation temperature <i>T</i><sub>exc</sub>, and OH radical particle number density will increase. On the contrary, although the voltage also increases as the pulse modulated duty cycle decreases, the gas temperature <i>T</i><sub>g</sub>, electron excitation temperature <i>T</i><sub>exc</sub>, and OH radical particle number density are all reduced. In addition, the results indicate that reducing the duty cycle of AC power can make the atmospheric pressure plasma jet produce more OH radicals at lower gas temperature. This study provides a new insight into the influence of electrical parameters on the characteristics of atmospheric pressure plasma jets under constant power, and also presents a guidance for choosing power parameters of plasma jets with low gas temperature and high density of reactive species, which is conducive to the development of atmospheric pressure plasma jets in biomedicine and other fields.

Effect of Working Coefficient on Induced Breakdown Characteristics of Plasma-Triggered-Based Gas Gap Switch in Fast Bypass Conditions

Gas gap switch (GGS) has obvious advantages in fast bypass operation, quick response, simple structure, and strong controllability. The working coefficient (i.e., the ratio of the main gap working voltage to the steady-state breakdown voltage) of GGS is mainly affected by the working voltage, the main gap distance, the type of trigger gas, and the pressure. However, the research mostly focuses on the influence of the above single factors on the trigger performance of GGS. There is a lack of studies on the induced breakdown characteristics of GGS considering the variation of the working coefficient under different factors. In this article, a research platform about the induced breakdown of GGS is established. It is shown that the working process of the GGS trigger cavity is divided into the high voltage pulse prebreakdown stage in the first cavity, the discharge ablation stage in the first cavity, and the discharge ablation stage in the second cavity. With the increase of the working voltage, the critical trigger capacitor voltage is lower, and the plasma jet characteristic parameters are decreased gradually during the critical conduction. The conduction time delay and time delay jitter are decreased rapidly, the triggering stability is significantly improved. Changing the main gap distance, the discharge channel shape is a significant difference at the moment of GGS-induced breakdown. And the electric characteristics of plasma jets are varied obviously. The high trigger gas pressure hinders the development of the plasma jet and causes a greater trigger jitter. With the increase of SF6 content in the trigger environment, the characteristic parameters of GGS decrease obviously. The strong insulation and electronegative gas seriously constrain the plasma jet capability. The research results can provide theoretical guidance for the improvement of trigger stability and the selection of trigger condition parameters of plasma-triggered-based gas switches used in fast bypass conditions.

Comparison of characteristics of atmospheric pressure plasma jets using argon and helium working gases

Dielectric Barrier Discharge (DBD) plasma jets have been studied extensively in recent years because of their wide range of applications. In this work, we studied the performance of a DBD cold atmospheric pressure plasma jet with neutral argon gas experimentally and compared the produced DBD argon plasma with the helium jet in an equivalent operation. We investigated the effect of applied voltage, flow rate, and electrodes configurations on the argon and helium plume length and analyzed the physical parameters of the plasma plume, including discharge voltage, average gas, temperatures of the discharge gap, and jet velocity in plasma-on mode via Pitot glass tube as a speedometer. The results showed that by increasing any of the applied voltage or the flow rate at low values in different electrodes arrangements, plumes shape are more homogeneous and their length increases, but the helium plasma plume is transient from laminar to turbulent flow mode at higher flow rates. The temperatures of the discharge gap between the electrodes and their surroundings in the argon jet had a large increase over the helium jet in an equi-operational. Speedometer results show that plasma discharge affects the speed of argon jet more than helium.

The Study of the Characteristics of a Microwave Plasma Jet Operated with Ar at Atmospheric pressure

In recent years, non-thermal atmospheric pressure plasma has attracted wide interest in industrial and biomedical fields due to its many advantages, such as its high efficiency, simple systems, easy operation, non-toxic residue, and low cost. In this project, non-thermal (cold) plasma generated using a voltage source with a precise frequency (microwave up to 2.4GHz) using argon gas. The electrical properties studied to describe the discharges of argon gas plasma jets at different flow rates (Flow= (1, 2, 3, 4) L/min) and with voltages (150 V). The produced plasma jet column will be analyzed using Optical Emission Spectrometry (OES) technology to determine plasma parameters such as electron temperature (Te), electron density (ne), plasma frequency (fp), Debye length (λD), and Debye (ND) number of the argon plasma jet. We use the Boltzmann plot to determine the electron temperature (Te) in the plasma, and the electron density (ne) is calculated by Stark broadening. The value of the electron temperature decreases from (0.991-1.273) eV and the electron density rises from (2.173-3.664) x1017 cm-3 with higher gas flow rates, also the Plasma plume length rises from (1.1-3.5) cm with higher gas flow rates, while the plasma jet temperature decreased with higher gas flow rates.