Plasma Jet Generator Research Articles

Generation and Characterization of Cold Atmospheric Pressure Plasma Jet for Surface Modification of High-Density Polyethylene

Cold atmospheric pressure plasma technology has a variety of applications in different fields including material science and biomedical science. It has been using for surface modification and material processing in material science and used to improve the wettability, adhesion and biocompability of polymeric surfaces without altering the entire bulk properties. This paper outlines the characterization of cold atmospheric pressure plasma jet, which was generated in a high frequency (20 kHz) and high voltage (3.5 kV) power supply, as well as its application in the surface modification of high density polyethylene. Electrical and optical characteristics are used to estimate the electron density of the plasma. The effect of plasma on the surface properties of the material are analyzed by calculating contact angle, surface energy measurements and analyzing scanning electron microscopy images. Adhesive bonding strength and numerous other attributes have increased, however surface treatment is the process of cleaning, etching, functionalizing, and chemically treating substrates to improve roughness and adhesive properties on the surface. Cold plasma can induce a soft roughening on the surface through ion bombardment with polar functional groups resulting in the decrease in water contact angle.

Estimating the power injection proportion of the plasma jet generator based on the measured enthalpy

The purpose of the developed plasma jet generator is to study the effect of jet plasma on electromagnetic wave propagation, simulating the plasma sheath environment encountered during space vehicle reentry. Because the temperature and velocity of the plasma jet are high, it is difficult to measure temperature and electron density by the contact method. In addition to the normal flow of the entire apparatus, high-power magnetic field energy (generated by the power supply) is injected into the inductively coupled plasma (ICP) generation region. The energy of the magnetic field excites the gas and generates plasma. In this paper, the whole apparatus is calculated numerically, the energy term is added to the corresponding area of ICP, and the enthalpy distribution of the whole apparatus is calculated. The heat flux and total pressure are measured by slug calorimeter (heat flux probe) and total pressure probe, and then, the enthalpy is obtained. When the calculated enthalpy is consistent with the measured enthalpy, the value of the energy term in the numerical calculation process is the injected energy value. The ratio of the energy injected into the ICP region to the total energy provided by the power supply is the power injection proportion. The power injection proportion of the apparatus in this paper obtained by the above method is between 25% and 30%.

Investigation of a cold atmospheric plasma jet generation in single and multichannel planar devices

A plasma source of atmospheric pressure with a planar geometry of the device and an adjustable number of planar discharge channels has been developed. The dependence of the recorded collector current on the amplitude of the applied voltage is investigated. It was found that the current in each of the channels consists of a set of independent current channels whose propagation does not depend on each other.

Unveiling the formation and control of unique swirling discharge pattern in helium plasma candle device

The generation of a large cold plasma jet while maintaining the reproducibility and homogeneity of the discharge is one of the major challenges encountered by the plasma community to efficiently apply this technology in the industry. Here, we report on the discharge in a recently developed device called the plasma candle (PC), wherein a stable plasma jet with a diameter of 20 mm can be generated at atmospheric pressure and temperature. Unlike the discharge morphology previously reported for conventional plasma jet devices, the unique configuration of PC device resulted in distinctive discharge patterns. Homogenous discharge was generated in the electrode gap and followed by a swirling discharge toward the tube nozzle. Fast photography and electrical measurements revealed that filament propagation and its morphology form the visually observable swirl discharge. Detailed analysis indicated that residual helium metastable species (Hem) and their penning ionization play an essential role in the discharge mode and its transition, which was verified by changing the feeding gas and the frequency of the applied voltage. For instance, it is found that only filamentary discharge was observed along the entire tube at frequencies less than 3 kHz, at which the time between consecutive discharges was long enough for Hem decay. Consequently, the homogenous discharge pattern was recovered by increasing the pre-ionization levels by adding a trace of impurities (N2, O2 or H2O) to the feeding gas. However, the level of these impurities must be carefully adjusted to achieve a homogenous discharge without negatively affecting the jet properties. A trivial change in the gas impurity, in the range of adsorption and desorption of water from the gas tubing, is sufficient to cause a noticeable change and instability in the discharge mode. This finding is critical to predicting the production of reactive species and plasma-surface interaction for different applications.

Effect of CF4 ratio on the interaction of atmospheric nanosecond pulsed He plasma jet with a dielectric material

In this paper, a two dimensional (2D) axisymmetric fluid model is built to study the effect of the ratio of CF4 admixture on the plasma dynamics and F-containing species concentration in He atmospheric pressure plasma jet. The steady mole fraction distribution of He and CF4 is first studied, which presents that the mole fractions of CF4 show peaks at 5 mm from the symmetry axis on the dielectric surface due to the dual influences of the boundary layer effect and air mixing. The CF4 admixture enhances the propagation speed of ionization wave, and the axial velocity reaches the peak value in the case of He + 1.5% CF4. The conversion from the ring-shaped plasma–surface interaction to a solid-disk one results from the addition of CF4. The Penning ionization of CF4 accelerates the plasma jet propagation within 1.5% CF4. However, the excitation energy loss and electron attachment caused by the addition of CF4 also quench the propagation of plasma jet, which become obvious in the case of 2% CF4. F-containing groups (CF4+, CF3+, CF3−, F−, CF3, and F), mainly produced by the Penning ionization reaction, electron attachment reaction, and He+ + CF4 → He + CF3+ + F, also show peaks for He + 1.5% CF4. On the dielectric surface, as the radial distance increases, the ratio of F-containing neutral species (CF3 and F) to O atom at 200 ns decreases due to the increase of O atom concentration and then increases at the streamer head because the surface flux of CF3 reaches the maximum value. The maximum surface flux radial distribution distance for ratio of F-containing species to O atom, CF3 and F appear in the case of 1.5% CF4.

Diagnostics of plasma jets in the solar corona

The paper discusses the diagnostics of plasma jets in the solar corona with the use of data from modern space- and ground-based telescopes observing the Sun in the extreme ultraviolet (EUV) and micro- wave bands. We examine observational parameters of EUV and radio emission in events associated with plasma jets, depending on the mechanism of formation, initiation conditions, and evolution of the jets. The opportunities provided by the study of plasma jets, which relies on simultaneous observations in different bands, are highlighted. For a number of jets, we have measured their primary parameters; and in this paper we present preliminary results of statistical processing of the data obtained. Microwave observations of several specific events, made by ground-based instruments RATAN-600, SRH, and Nobeyama Radioheliograph, are considered in detail. The diagnostic capabilities of these instruments for studying coronal jets are shown. To analyze the three-dimensional structure of the coronal magnetic field, we have used SDO/HMI data, which allowed for the reconstruction of the field in the lower corona. The information gained is compared with the results of diagnostics of the magnetic field at the base of the corona according to RATAN-600 data. The purpose of the methods developed is to determine the physical mechanisms responsible for the generation, collimation, and dynamics of plasma jets in the solar atmosphere.

Диагностика плазменных струй в короне Солнца

The paper discusses the diagnostics of plasma jets in the solar corona with the use of data from modern space- and ground-based telescopes observing the Sun in the extreme ultraviolet (EUV) and micro- wave bands. We examine observational parameters of EUV and radio emission in events associated with plasma jets, depending on the mechanism of formation, initiation conditions, and evolution of the jets. The opportunities provided by the study of plasma jets, which relies on simultaneous observations in different bands, are highlighted. For a number of jets, we have measured their primary parameters; and in this paper we present preliminary results of statistical processing of the data obtained. Microwave observations of several specific events, made by ground-based instruments RATAN-600, SRH, and Nobeyama Radioheliograph, are considered in detail. The diagnostic capabilities of these instruments for studying coronal jets are shown. To analyze the three-dimensional structure of the coronal magnetic field, we have used SDO/HMI data, which allowed for the reconstruction of the field in the lower corona. The information gained is compared with the results of diagnostics of the magnetic field at the base of the corona according to RATAN-600 data. The purpose of the methods developed is to determine the physical mechanisms responsible for the generation, collimation, and dynamics of plasma jets in the solar atmosphere.

Investigation of Compact Hollow-Anode Discharge Source for Copper Thin Films by Sputtering Processes

A compact hollow-anode discharge (HAD) source with a size of 60 mm in radius and 70 mm in length has been developed to stably generate plasma jets for various sputtering processes in semiconductor and display fabrications. A developed HAD plasma source has been investigated by cylindrical electric probes, and the experimental results were compared to the values of numerical calculations. A uniform density discharge model with a geometry factor was proposed to estimate the profiles of plasma parameters. Owing to the difference of absolute magnitude, even with the similar trend of spatial variation, plasma parameters such as electron temperature (Te) and plasma density (ne) measured at z = 3 cm have been calibrated by the values of numerical calculations at the nozzle entrance (z = 0 cm, at the throat of the jet), and the calibration factors for Te and n0 have been deduced by comparing the experimental values to numerical calculations. These are to be explained by the decay mechanism along the axis of the jet with elastic collisions in terms of the mean free path. The developed HAD plasma source was tested for the deposition of Cu thin films with an optimized condition as a plausible application to sputtering processes.

Электрофизические и тепловые параметры плазменной струи атмосферного давления в гелии при возбуждении синусоидальным и импульсным напряжением

Comparative studies of generation of cold plasma jet of atmospheric pressure in helium when excited by sinusoidal voltage and unipolar positive pulses at 2-6 kV for medical applications have been conducted. It is shown that the achieved parameters are identical, but the absence of the effect of frequency self-organization of streamer breakdown leading to irregularity in streamer propagation under pulse excitation makes it preferable in biophysical experiments. A limiting factor for plasma jet exposure is the achievable target temperature, which can be reduced by limiting the duration of the current.

Physical interpretation of a pulsed atmospheric pressure plasma jet following parametric study of the UV–to–NIR emission

In the present report, an atmospheric pressure plasma jet is sustained in a helium channel by high square wave unipolar voltage. The gas flow rate and the square wave features (amplitude, frequency, and duty cycle) are varied over a wide range, while the plasma ultraviolet to near infrared emission is recorded. The plasma emission pattern, the propagation dynamics of the involved ionization fronts, the relative density of critical excited species, and the rotational and vibrational temperatures of neutral and ionic species are measured. An optimum operational window is found corresponding to a helium flow rate of 2 slm, a pulse amplitude of 7.5 kV, a pulse repetition rate of 10 kHz, and a pulse duty cycle of 5%–7%. Under these conditions, a plasma jet length close to 45 mm and a gas temperature close to 325 K are obtained, while a high yield of OH, N2(SPS), N2+(FNS), N2(FPS), He*, O*, and NOγ is achieved. The results are found to be in good agreement with the bibliography and motivate a consideration on the involved physical mechanisms. The plasma jet propagation with respect to the reactive species production is discussed based on the local electric field variation over the high voltage pulse width.

Study on generation characteristics of plasma jets of multi-electrode in a pulse vacuum discharge

In order to increase the production of plasma jets in a pulse vacuum discharge, based on the insulated anode electrode structure (IAES), discharge experiments by using multiple electrodes under one power supply are performed in this paper. During experiments, discharge currents flowing through multiple cathode sides (cathode currents) were measured by identical Rogowski coils at the same time. The plasma density and propagation velocity of plasma jets were measured by the self-designed ‘+’ type probes. Firstly, the differences in discharge characteristics and generation characteristics of plasma jets between the single-electrode and the double-electrode discharge were compared and analyzed. Secondly, the effects that the electrode spacing (D) and the capacitor capacity had on the discharge characteristics and generation characteristics of plasma jets of the multi-electrode were analyzed. Results show that because the discharge voltage of the IAES is dropped to the arc voltage after a long duration, the simultaneous discharge of multiple electrodes in a single pulse can be realized. Compared with the single-electrode discharge, using multiple electrodes to discharge simultaneously in a single pulse can decrease the initial discharge voltage, increase the peak of cathode current and increase the amount of plasma production. In addition, there is interaction between plasma jets of the multi-electrode, and the spatial electric field generated by the first ejected plasma jet will hinder the generation of plasma jets of subsequent electrodes. Only by keeping a certain electrode spacing (D) between the electrodes, can multiple electrodes be all discharged and plasma jets of the same length be produced. Increasing capacitor capacity can increase the plasma density, propagation velocity, length of plasma jets of the multi-electrode, and realize the simultaneous discharge of more electrodes in a single pulse.

Atmospheric pressure plasma jet powered by piezoelectric direct discharge

AbstractThe piezoelectric direct discharge sustained using a high‐performance piezoelectric transformer (PT) with a voltage transformation ratio of >1,000 was used for the generation of an atmospheric pressure plasma jet (APPJ). The ionization gases used are ambient air and compressed dry air. The APPJ was characterized using capacitive probe measurement, ozone concentration measurement, and activation area determination. The activation experiments were conducted on a high‐density polyethylene. The activation area was visualized using pure formamide test ink (58 mN/m) and captured by a digital camera. The influence of gas flow, PT power, and the distance between the PT and the substrate were investigated.

The origin of plasma jets generated in Z-pinch discharges

The results of modeling in the framework of magnetic hydrodynamics (MHD) for the development of a plasma jet in Z-pinches are presented. It has been shown that plasma jet origin is associated with the development of MHD instability m = 0, but not with the conical current sheath structure. MHD modeling is also carried out for θ-pinch systems where generation of plasma jets is much less effective. The corresponding analysis is presented.

Generation of cold atmospheric plasma jet by a coaxial double dielectric barrier reactor

In this study, the generation of cold atmospheric plasma jet was investigated in a coaxial double dielectric barrier configuration conjugated with a microsecond voltage pulse generator. The advanced reactor comprised two coaxial dielectric tubes of different diameters with two ring-shaped electrodes covering outside the larger tube. The electrodes were immersed in a liquid dielectric (i.e. transformer oil) in order to isolate them from the ambient air, which completely prevented the direct sparks formation between them within the investigated range of the applied voltage. The He discharge gas was fed to the inner tube while either air, N2, or O2 as a shielding gas was introduced into the gap between the two dielectrics. The result revealed that with these shielding gases, the unwanted abnormal discharge in the inter-dielectric gap was extinguished and the plasma discharge occurred only in the He gas in the inner tube. Consequently, the electrical power delivered to the He discharges maintained at a level of around 1 W with a considerable variation in the applied voltage. Meanwhile, the discharge power of the unshielded jet was almost tripled as the applied voltage was increased from 7 to 10 kV. Interestingly, the cold plasma jet generated by the alternative reactor design in this study, which had the electron density up to 2.5 × 1013 cm−3, consumed relatively less He gas with less restriction on the high voltage range applied. The design also enhanced the possibility to control the plasma chemistry and jet temperature by changing the shielding gas. Therefore, the reactor is capable of producing a cold atmospheric plasma jet for the emerging plasma application such as plasma medicine and bio-applications.

Power Supply for Generation of Low-Temperature Plasma Jets

The results of an investigation of the regimes of operation of a specialized power supply, functioning in a system for generation of plasma jets based on a low-current glow discharge sustained at an atmospheric pressure, are presented. The power supply ensures different modes of operation of a nonsteady-state low-current plasmatron relying on a glow discharge in an air flow at the average discharge currents up to 0.15 A and air flow rates up to 0.8 l/s.

Generation and Characterization of an Atmospheric-Pressure Plasma Jet (APPJ) and Its Application in the Surface Modification of Polyethylene Terephthalate

An atmospheric-pressure plasma jet (APPJ) has a lot of applications in recent years such as in material processing, surface modification, biomedical material processing, and thin film deposition. APPJ has been generated by a high-voltage power supply (0-20 kV) at an operating frequency of 27 kHz. This paper reports the generation and characterization of APPJ in argon environment and its application in the surface modification of polyethylene terephthalate (PET). The plasma jet has been characterized by electrical and optical methods. In order to characterize the plasma jet, electron density and electron temperature have been determined. The surface roughness of the untreated and plasma-treated PET samples was characterized by contact angle measurement, surface energy analysis, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM).

The effect of mixed electric field on characteristic of Ar–N2 plasma jets for TiN surface treatment

In this paper, we present a new structure for Ar–N2 plasma jet generation where a pulsed electric field is modified with a second alternating electric field, referred to as mixed electric field. The electric field distribution through the jet tube is simulated for the conventional and newly designed plasma jet. It is demonstrated that the value of the electric field becomes stronger due to mixed electric field, particularly between the tip and ring electrodes through the tube. Not only does the length of plasma jet increase from 15 cm to 30 cm when a mixed electric field is employed, but also the temperature of the substrate surface decreases from 62 °C to 52 °C at the same power, which is favorable for industrial applications. It is shown that introducing more nitrogen into the plasma jet shortens the length of the jet, while the jet length could substantially be improved using the current design. The capability of surface treatment at different electrical power is also evaluated on deposited TiN layers by the conventional and current plasma jet. The surface treatment by the newly designed plasma jet based on mixed electric field shows no detectable damage on the TiN layer, while the conventional plasma jet degrades the surface at equal power. The hydrophilicity of the surface is also measured by the contact angle of a water droplet, which decreases from 66 to 31° after surface treatment, implying the surface becomes more hydrophilic. The temperature distribution on the substrate is also evaluated for Ar–N2 plasma jet and compared with the conventional plasma jet structure.

Electromagnetic plasma rail accelerator for surface analysis and modification in solids

In this study we investigate the possibility of using plasma rail accelerator as a dense plasma jet generator for scientific and technological purposes. It was found that plasma railgun can generate supersonic plasma jets, both pure and saturated with solid and liquid microparticles. Such jets can cause thermal and mechanical erosion of the target surface, sputtering material of the railgun channel and transferring it to the surface being treated. We studied working regimes of the plasma railgun. SEM and optical micrographs of the treated samples were obtained.

Study of two positive current pulses atmospheric pressure cold plasma jet

Simple argon atmospheric pressure cold plasma jet has been designed and characterized. The spectral and electrical characteristics of the generated plasma jet were investigated. The effects of applied voltage and flow rate on plasma jet length were studied. A sinusoidal high voltage waveform was applied to ignite the plasma jet. Two current pulses were generated per each half cycle of the positive applied voltage while one current pulse was generated in the negative halves of the voltage waveforms. The time interval between the two positive current pulses decreased with increasing the applied voltage. The emission spectra of the plasma specified that the plasma included active species of O• and OH•. In addition, the estimated gas temperature of the generated plasma jet was in the range of 330 K, which nominated this jet to be used to treat heat sensitive materials. The obtained results showed that the length of the plasma jet increased by increasing any of the applied voltage or the flow rate at low values, whereas the length approached steady-state values at higher applied voltages and transient from laminar to turbulent flow mode at higher flow rates. This work is highly useful for applications of the required exposure to active species, charged ions, and UV photons at low operating temperatures and applied voltages.

Temporal evolution of the relative vibrational population of N2 (C3∏u) and optical emission spectra of atmospheric pressure plasma jets in He mixtures

In this study, spatial-temporal resolved optical emission spectroscopy and electrical characteristics are employed to study the dynamic evolution of molecules, vibrational distributions, reactive species, and streamer head speed in the generation and propagation of atmospheric pressure plasma jets (APPJs). The images of discharge, waveforms of pulse peak voltage and discharge current, and spatial-temporal emission spectra of N2 (C3Πu → B3Πg, 380.5 nm), (B2 → X2, 391.4 nm) and He (3s3S → 2p 3P, 706.5 nm) are recorded, the relative vibration population of N2 (C3Πu) and the key dynamic process of each discharge pulse are discussed. The effects of pulse peak voltage on emission intensity, vibration population of N2 (C3Πu) and APPJ speed are also investigated. The results show that the streamer head speed is about 105 m s−1 under the pulse peak voltage of 5–9 kV, and both the streamer head speed and emission intensities increase with pulse peak voltage. The emission intensities of N2 (C3Πu → B3Πg, 380.5 nm) rise for about 10 ns but fall for several tens of nanoseconds. During the plasma generation process, the direct electron impact process is dominant in generating electronic, vibrationally and rotationally excited N2. Several tens of nanoseconds after the generation, spontaneous emission, quenched by N2 and O2 dominate the decay process. While the step excitation and Penning ionization extend the duration time of emission intensity. It is also found that the ratio of N2 (C, υ = 1)/N2 (C, υ = 0) is at high level within . The evolution of the ratio is dominated by the direct electron impact in the initial time, and is then possibly influenced by the vibrational relaxation process and downward vibrational–vibrational energy transmission process.