Behavior Of Plasma Jet Research Articles

Exploring the connection between non‐uniform electrostatic fields generated by opposite polarity voltages and the behavior of atmospheric pressure plasma jet

AbstractThis study investigates the counterintuitive behaviors of a microwave‐induced atmospheric pressure plasma jet (APPJ) under the influence of an external electrostatic field applied by one or a pair of parallel electrode plates subjected to DC voltages. The findings demonstrate that the plasma jet consistently deflects toward the electrode plate with an electrostatic potential, irrespective of the direction of the applied field. The deflection becomes more pronounced with increasing voltage on the electrode plate until the ionic wind generated by the high voltage significantly affects the jet's behavior. Remarkably, a negative voltage induces a greater deflection compared to a positive voltage. To further investigate this discovery, the dielectric properties and the non‐neutral characteristics of the APPJ are analyzed, and the simulations of the electric field distribution reveal a non‐uniform distribution, which plays a crucial role in understanding the mechanism behind the observed behaviors of the plasma jet. This study provides a comprehensive understanding of the underlying mechanism driving the observed phenomena and sheds light on the collective behavior of plasma jets under non‐uniform electric fields. The findings of this study offer valuable guidelines for investigating and controlling the behavior of APPJs.

Investigation of the behavior of plasma jet in the presence of water under different grounded conditions

AbstractPrevious researches have demonstrated that the ground electrode would influence the performance of the plasma jet. In this study, the characteristics of plasma jets underwater for different grounded conditions are investigated. The influence of airflow rate, and electrode length underwater are experimental studies. When the water is grounded, it would provide another charge channel for the discharge, much more ions would be transferred to the water. The length and discharge intensity would be enhanced. Besides, the length of electrode underwater would also influence the performance of the plasma jet. It is found that the shorter the electrode length, the larger the ratio of plasma jet length to electrode length. Furthermore, an electric diagram is promoted to explain the corresponding mechanism, by analyzing the resistance and capacitance under different working conditions, the theoretical explanation under different experimental working conditions is given, and further analysis demonstrated that the accumulation of charges in water during the discharge process would be the main reason to influence the propagation of plasma jet under water.

Numerical study of helium atmospheric pressure plasma jet interacting with a wavy substrate surface with different dielectric constants and curvature radius

In this paper, we present a two-dimensional numerical study on a helium atmospheric pressure plasma jet interacting with a wavy substrate surface, focusing on the effects of the substrate relative dielectric constant and substrate morphologies on the plasma jet behavior near the wavy surface. The results show that when the dielectric constant is small, the jet can form separate discharge channels near the wavy substrate surface and can penetrate the cavity of the wavy substrate surface. With increasing dielectric constant, the penetration distance of the discharge channels decreases. When the substrate dielectric constant exceeds a certain value, the plasma jet only propagates above the wavy substrate surface and there are no prominent separated channels near the surface. Meanwhile, the radial propagation distance along the substrate surface decreases. For a certain dielectric constant, the penetration depth of the separated channel depends on the curvature radius of the wavy substrate surface and there exists a minimum curvature radius that allows the separated channel to enter the cavity. This minimum curvature radius varies with the substrate dielectric constant. If the dielectric constant becomes larger, the minimum curvature radius increases.

Characterization of an atmospheric pressure plasma jet producing the auroral transition O(1S) to O(1D)

We present a detailed characterization of an atmospheric pressure plasma jet that produces the metastable oxygen states O(1S) and OD) with emission of the ‘auroral’ green line. The device used 99.999 pure argon as a working gas for the plasma generation. Optical emission spectroscopy was used to understand the active species present in the plasma jet and to infer the mechanism of O(1S) creation and destruction. The continuum spectrum was used in conjunction with a method based on machine learning for determining the arbitrary electron probability distribution function. Discharge and plasma properties were estimated from Lissajous plots and using calculations with the BOLSIG+ software. The metastable oxygen forms for all operating parameters of the plasma jet system in a linear electrode configuration. The camera images provided information of the overall plasma jet behavior as parameters were altered. While the metastable oxygen was produced for every iteration, the plasma jet behavior changed considerably when the powered and grounded electrodes are switched. Small admixtures of oxygen and nitrogen were introduced in the plasma jet to understand the kinetic processes of metastable oxygen destruction and the 557.7 nm auroral line. This behavior has implications for plasma reactive chemistry in fundamental areas such as auroral physics as well as technological applications of plasmas.

Atmospheric Plasma Meets Cell: Plasma Tailoring by Living Cells.

The applications of the cold atmospheric plasma jet (CAPJ) in cancer treatment have been investigated for over a decade, focused on the effect that the CAPJ creates on cancer cells. Here we report for the first time on the impact that cells have on the CAPJ during treatment. To better understand these CAPJ-cell interactions, we analyzed the CAPJ behaviors in the presence of several normal and cancer cell lines and investigated the CAPJ selectivity. A more in-depth study of plasma self-organization patterns utilizing a model which contains a combination of normal and cancer cells reveals that the cells' capacitance can be an important predictor of plasma jet behavior. Cancer cells can direct the jet either toward or away from normal cells, which depends on the boundary condition behind the cell colony. Both experimental and theoretical results show that a grounded copper board beneath the cell-culture dish leads to opposite CPAJ behaviors compared with a floating boundary condition. In conclusion, our findings indicate that plasma can be self-adaptive toward cancer cells, and such a feature can be manipulated. Therefore, using the permittivity difference among cell lines may help us focus plasmas upon cancer cells at the vicinity of normal tissues and maximize the selectivity of plasma treatments.

Transport and deposition behaviors of vapor coating materials in plasma spray-physical vapor deposition

The plasma spray-physical vapor deposition (PS-PVD) technology offers great potential to support the development of non-line-of-sight deposition. However, many researches indicated that the shadowing effect is a significant mechanism of PS-PVD for the coating growth and formation of the micro-structure. There seems to be an irreconcilable contradiction between the two theories. In this study, both the transport and deposition behavior of PS-PVD processes are researched from a macroscopic and microscopic perspective, respectively. The deposition processes of vapor coating materials are separated by the last collision position. The process before reaching the last collision position is defined as transport behavior, and the process after the last collision position is defined as deposition behavior. The results of simulation and experiment indicated that the flow behavior of plasma jet and the frequent collisions between plasma gas and vapor coating material provide opportunities for the vapor coating material to deposit in shadowed surfaces or non-line-of-sight positions. The shadowing effect under micro line-of-sight deposition is a major factor in the growth of columnar structures, and it accompanies the entire process of coating growth. This study divides the deposition process of vapor coating materials into the macro non-line-of-sight transport and micro line-of-sight deposition, illuminates the macro-non-line-of-sight transport behavior of vapor-phase materials, and sheds light upon the micro-line-of-sight deposition mechanism of the PS-PVD process.

Time-Resolved Observation of Plasma Jets Synchronized With Fibered Optical Wave Microphone Measurement

Our concern with plasma jets is the generation of pressure waves that influence the surface or the inside of targets. In this paper, the detection of pressure waves emitted from plasma jets was carried out using a fibered optical wave microphone, which works based on Fraunhofer diffraction for phase objects, with a synchronized high-speed camera observation of the dynamic behavior of plasma jets and their electrical properties. The electrode configuration of typical dielectric barrier discharge tubes was used in He gas flow. Effects of the amplitude and frequency of applied voltages and He gas flow rates on relationships among the irradiation of plasma jets, the generation of pressure waves, and current waveform were studied. Pressure waves were detectable by the fibered optical wave microphone, even though the irradiation of plasma jets from the glass tube was not observed with the high-speed camera. Frequency dependence on the generation of pressure waves was confirmed.

On atmospheric-pressure non-equilibrium plasma jets and plasma bullets

Atmospheric-pressure non-equilibrium plasma jets (APNP-Js), which generate plasma in open space rather than in a confined discharge gap, have recently been a topic of great interest. In this paper, the development of APNP-Js will be reviewed. Firstly, the APNP-Js are grouped based on the type of gas used to ignite them and their characteristics are discussed in detail. Secondly, one of the most interesting phenomena of APNP-Js, the ‘plasma bullet’, is discussed and its behavior described. Thirdly, the very recent developments on the behavior of plasma jets when launched in a controlled environment and pressure are also introduced. This is followed by a discussion on the interaction between plasma jets. Finally, perspectives on APNP-J research are presented.

S055033 音波制御した大気圧プラズマジェットによる表面改質効果

The aim of this investigation is to reveal how the working gas behavior affects the motion of a microwave discharged atmospheric pressure plasma jet (APPJ) in surface modification process on a flat glass plate. The motion of APPJ with argon was actively controlled by sound wave. The periodic excitation was locally irradiated at the jet shear layer. The behavior of plasma jet and working gas were directly captured by a high speed digital CCD camera for symmetric or asymmetric modes. As a result, the plasma jet is stable under no-excitation condition. On the contrast, periodic meandering motion in the excitation direction was observed under the both of symmetric and asymmetric excitation. The plasma jet amplitude for asymmetric excitation is much larger than that for symmetric excitation.

ICCD Imaging of Atmospheric Pressure Plasma Jet Behavior in Different Electrode Configurations

Nowadays, atmospheric pressure plasma jets using a dielectric-barrier discharge with an axial symmetry configuration attract the interest of many researchers. However, the mechanisms responsible for the generation of atmospheric plasma jets still remain unknown. In this paper, using intensified charge-coupled device images, we present the “bulletlike” structures of a plasma jet traveling at supersonic velocities.

OH number densities and plasma jet behavior in atmospheric microwave plasma jets operating with different plasma gases (Ar, Ar/N2, and Ar/O2)

OH radical number density in multiple atmospheric pressure microwave plasma jets is measured using UV cavity ringdown spectroscopy of the OH (A–X) (0–0) band at 308 nm. The plasma cavity was excited by a 2.45 GHz microwave plasma source and plasma jets of 2–12 mm long were generated by using three different plasma gases, argon (Ar), Ar/N2, and Ar/O2. Comparative characterization of the plasma jets in terms of plasma shape, stability, gas temperature, emission intensities of OH, NO, and N2, and absolute number density of the OH radical was carried out under different plasma gas flow rates and powers at various locations along the plasma jet axis. With three different operating gases, the presence of OH radicals in all of the plasma jets extended to the far downstream. As compared to the argon plasma jets, the plasma jets formed with Ar/N2 and Ar/O2 are more diffuse and less stable. Plasma gas temperatures along the jet axis were measured to be in the range of 470–800 K for all of the jets formed in the different gas mixtures. In each plasma jet, OH number density decreases along the jet axis from the highest OH density in the vicinity of the jet tip to the lowest in the far downstream. OH density ranges from 1.3 × 1012 to 1.1 × 1016, 4.1 × 1013 to 3.9 × 1015, and 7.0 × 1012 to 4.6 × 1016 molecule/cm3 in the Ar, Ar/N2, and Ar/O2 plasma jets, respectively. The OH density dependence on plasma power and gas flow rate in the three plasma jets is also investigated.

Integrated Robotic Plasma Spraying System for Advanced Materials Processing

During atmospheric plasma spraying (APS), to control the time dependent D.C. plasma jet behavior requires the comprehensive understanding of its electric, magnetic, thermal, thermodynamic phenomena. In this paper, influence of particles injection with the form of suspension on the fluctuation of plasma jet is analyzed, and a control approach is presented to eliminate the effect. Moreover, an integrated robotic plasma spraying system for advanced materials processing, i.e., rapid metal tooling and solid oxide fuel cell (SOFC), is developed, which combines a PC-based controller with a six-aids robot. The intelligent adaptive adjustment of robot spraying trajectories and self-dispatch of manufacturing strategies were carried out by the resultant system according to the feedback of the temperature and thickness of sprayed coatings and other information during plasma praying. The flexibility of the forming system was promoted by integrating plasma spray forming with robot motion control. Excellent control performance is observed and this system can be effective to meet the requirements of different materials processing techniques.

Behavior of underexpanded plasma jet in strong magnetic field

A visual study of underexpanded plasma jet was conducted to reveal the detailed behavior in the strong magnetic field. The images of the jet were taken by a digital single-lens reflex camera through viewing windows. The distribution of optical intensity obtained from the raw data was compared to that of the typical emission line intensity. The profile of the optical intensity agrees well with that of the emission intensity. It is illustrated that the typical structure of underexpanded jet such as Mach disk is also affected obviously by the magnetic field. The radial distribution of number density was determined by using the image analysis based on the Abel-inversion. The converted data clarify the jet behavior that is hidden on the ordinary observation. The density obtained from numerical analysis for a simple gas was also compared with the number density. It is confirmed from the comparison with numerical results that the radial profile of number density can be utilized for understanding the plasma jet behavior under the strong magnetic field.

Effect of Anode Arc Root Position on the Behavior of the DC Non-transferred Plasma Jet at Field Free Region

A special bi-anode plasma torch that can change the anode arc root position without changing working gas flow rate has been developed to investigate the effect of anode arc root position on the behavior of the plasma jet. It has two nozzle-shaped anodes at different axial distances from the cathode tip. The arc root can be formed at anodes either close to the cathode tip (anode I) or far away from it (anode II) to obtain different attachment positions and arc voltages. The characteristics of pure argon plasma jets operated in different anode modes were measured in the field free region by using an emalpy probe, and the thermal efficiency of the torch was determined by measuring the temperature differences between cooling water flowing in and out of the torch. The results show that compared with the normal arc operated in anode I mode, the elongated arc operated in anode II mode significantly reduced the plasma energy loss inside the torch, resulting in a higher temperature and a higher velocity of the plasma jet in the field free region.

Plasma electrode-type plasma spray gun—effect of powder loading on the behavior of plasma jet

A newly designed plasma electrode-type plasma spray gun, which can generate a high temperature and clean plasma jet and inject various materials into the center of the arc column, has been developed. In order to demonstrate the application feasibility of this new-type plasma spray gun for thermal plasma processing, the effects of powder loading on the stability and temperature of the plasma jet and on the electrode spot were studied. It was clarified that with powder loading, the plasma jet was very stable and not contaminated by electrode materials, i.e. clean, and the extent of the jet temperature decrease was a little, i.e. about 1000 K.

Plasma jet behavior and modeling associated with the plasma spray process

In the first part of this overview, the behavior of a typical plasma spray jet will be discussed, including the effects of arc behavior on the jet, transition to turbulence, gas entrainment, jet instabilities, demixing effects and the associated problems of measuring temperature and velocity fields using spectroscopy and enthalpy probes. The second part will be devoted to modeling attempts of the plasma jet, and modeling results will be presented of particle behavior in a plasma jet, including particle trajectories, particle velocities, and their heating histories.