In the last 30 days

• Open/close Kinetic scheme of the non-equilibrium discharge in nitrogen-oxygen mixtures

  I A Kossyi et al 1992 Plasma Sources Sci. Technol. 1 207 Tag this article

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  A kinetic scheme for non-equilibrium discharge in nitrogen-oxygen mixtures is developed, which almost wholly describes chemical transformations of particles in the cold (200 K<or=T<or=500 K) vibrationally unexcited gas. The kinetic scheme includes processes of excitation of electronic states, destruction and ionization of heavy particles by electron impact, associative ionization, electron attachment and detachment, electron-ion and ion-ion recombination, chemical transformations of neutral particles (in ground and excited electronic states) and ion conversion. On the basis of kinetic modelling in the framework of the kinetic scheme proposed, the influence of the electronic excitations of nitrogen molecules and atoms on air composition dynamics is analysed.

• Open/close Plasmas as metamaterials: a review

  Osamu Sakai and Kunihide Tachibana 2012 Plasma Sources Sci. Technol. 21 013001 Tag this article

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  When we form a structure of plasmas distributed in a certain space in which electromagnetic waves propagate, such a plasma structure serves as a different medium from a homogeneous bulk plasma. We can also enhance or generate novel functions of the plasmas when we add other structural materials such as functional components. That is to say, when we estimate such a medium from the material properties such as permittivity, permeability and conductivity, it shows extraordinary and/or functional effects that arise from the synthesis of the structure. We call such an artificial material a plasma metamaterial. In this review, starting from a fundamental understanding of electromagnetic wave propagation in and around plasmas, we review the new functions of plasmas as metamaterials, including a photonic-crystal-like behavior, a negative refractive index state and a nonlinear bifurcated electric response, by describing specific plasma structures. In addition, we survey some specific applications of such media and predict a feasible scientific expansion of this field in the near future.

• Open/close On atmospheric-pressure non-equilibrium plasma jets and plasma bullets

  X Lu et al 2012 Plasma Sources Sci. Technol. 21 034005 Tag this article

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  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.

• Open/close Ion energy distribution measurements in rf and pulsed dc plasma discharges

  D Gahan et al 2012 Plasma Sources Sci. Technol. 21 024004 Tag this article

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  A commercial retarding field analyzer is used to measure the time-averaged ion energy distributions of impacting ions at the powered electrode in a 13.56 MHz driven, capacitively coupled, parallel plate discharge operated at low pressure. The study is carried out in argon discharges at 10 mTorr where the sheaths are assumed to be collisionless. The analyzer is mounted flush with the powered electrode surface where the impacting ion and electron energy distributions are measured for a range of discharge powers. A circuit model of the discharge, in combination with analytical solutions for the ion energy distribution in radio-frequency sheaths, is used to calculate other important plasma parameters from the measured energy distributions. Radio-frequency compensated Langmuir probe measurements provide a comparison with the retarding field analyzer data. The time-resolved capability of the retarding field analyzer is also demonstrated in a separate pulsed dc magnetron reactor. The analyzer is mounted on the floating substrate holder and ion energy distributions of the impinging ions on a growing film, with 100 ns time resolution, are measured through a pulse period of applied magnetron power, which are crucial for the control of the microstructure and properties of the deposited films.

• Open/close Plasma generation and plasma sources

  H Conrads and M Schmidt 2000 Plasma Sources Sci. Technol. 9 441 Tag this article

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  This paper reviews the most commonly used methods for the generation of plasmas with special emphasis on non-thermal, low-temperature plasmas for technological applications. We also discuss various technical realizations of plasma sources for selected applications. This paper is further limited to the discussion of plasma generation methods that employ electric fields. The various plasmas described include dc glow discharges, either operated continuously (CW) or pulsed, capacitively and inductively coupled rf discharges, helicon discharges, and microwave discharges. Various examples of technical realizations of plasmas in closed structures (cavities), in open structures (surfatron, planar plasma source), and in magnetic fields (electron cyclotron resonance sources) are discussed in detail. Finally, we mention dielectric barrier discharges as convenient sources of non-thermal plasmas at high pressures (up to atmospheric pressure) and beam-produced plasmas. It is the main objective of this paper to give an overview of the wide range of diverse plasma generation methods and plasma sources and highlight the broad spectrum of plasma properties which, in turn, lead to a wide range of diverse technological and technical applications.

• Open/close Dynamics of dielectric barrier discharges in different arrangements

  Valentin I Gibalov and Gerhard J Pietsch 2012 Plasma Sources Sci. Technol. 21 024010 Tag this article

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  Based on experimental results, numerical investigations of dielectric barrier discharges (DBDs) have been performed in three basic configurations: in the volume, coplanar and surface discharge arrangements. It is shown that the DBD dynamics is the same in all arrangements and it is determined by the development of a few principal constituents, i.e. cathode- and anode-directed streamers, discharge channel, cathode layer and surface charges. It is found that the anode- and cathode-directed streamers appear with a highly conductive channel in between. The interaction of the streamers with conductive and dielectric surfaces determines the filamentary or homogeneous appearance of the discharge and its properties. The cathode-directed streamer is a self-sustaining phenomenon, which moves in a gas gap or along an electrode driven by a positive loop-back between photoemission and electron multiplication. The anode-directed streamer plays a subsidiary role. Depending on the kind of gas (electronegative or electropositive) and/or the degree of development of the cathode-directed streamer, the field strength in the conductive channels changes significantly. When the cathode-directed streamer touches the electrode surface, a cathode layer appears with parameters close to those of normal glow discharges. In volume discharge arrangements the movement of the streamers results in the appearance of Lichtenberg figures on dielectric surfaces.

• Open/close Atmospheric pressure ionization waves propagating through a flexible high aspect ratio capillary channel and impinging upon a target

  Zhongmin Xiong and Mark J Kushner 2012 Plasma Sources Sci. Technol. 21 034001 Tag this article

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  Atmospheric pressure ionization waves (IWs) propagating in flexible capillary tubes are a unique way of transporting a plasma and its active species to remote sites for applications such as biomedical procedures, particularly in endoscopic procedures. The propagation mechanisms for such IWs in tubes having aspect ratios of hundreds to thousands are not clear. In this paper, results are discussed from a numerical investigation of the fundamental properties of ionization waves generated by nanosecond voltage pulses inside a 15 cm long, 600 µm wide (aspect ratio 250), flexible dielectric channel. The channel, filled with a Ne/Xe = 99.9/0.1 gas mixture at 1 atm, empties into a small chamber separated from a target substrate by 1 cm. The IWs propagate through the entire length of the channel while maintaining similar strength and magnitude. Upon exiting the channel into the chamber, the IW induces a second streamer discharge at the channel–chamber junction. This streamer then propagates across the chamber and impinges upon the target. The average speeds of the capillary-bounded IW are about 5 × 10 ⁷ cm s ⁻¹ and 1 × 10 ⁸ cm s ⁻¹ for positive and negative polarities, respectively. The propagation speed is sensitive to the curvature of the channel. In both cases, the peak in ionization tends to be located along the channel walls and alternates from side-to-side depending on the direction of the local instantaneous electric field and curvature of the channel. The ionization region following the IW extends up to several centimeters inside the channel, as opposed to being highly localized at the ionization front in unconstrained, atmospheric pressure IWs. The maximum speed of the IW in the chamber is about twice that in the channel.

• Open/close Atomic oxygen in a cold argon plasma jet: TALIF spectroscopy in ambient air with modelling and measurements of ambient species diffusion

  S Reuter et al 2012 Plasma Sources Sci. Technol. 21 024005 Tag this article

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  By investigating the atomic oxygen density in its effluent, two-photon absorption laser-induced fluorescence (TALIF) spectroscopy measurements are for the first time performed in a cold argon/oxygen atmospheric pressure plasma jet. The measurements are carried out in ambient air and quenching by inflowing air species is considered. We propose a novel absorption technique in the VUV spectral range, where emission originating from within the discharge is used as light source to determine the inflow of atmospheric oxygen into the effluent. Furthermore, we propose a modelling solution for the on-axis density of inflowing ambient air based on the stationary convection–diffusion equation.

• Open/close Possibilities of determining non-Maxwellian EEDFs from the OES line-ratios in low-pressure capacitive and inductive plasmas containing argon and krypton

  Xi-Ming Zhu et al 2012 Plasma Sources Sci. Technol. 21 024003 Tag this article

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  Optical emission spectroscopy (OES) is classically used to determine the electron temperature in low-temperature plasmas by assuming a Maxwellian electron energy distribution function (EEDF). However, non-Maxwellian EEDFs are often found in these plasmas. In this work, we propose an OES line-ratio method that is aimed at obtaining non-Maxwellian EEDFs, with a collisional–radiative model of argon and krypton. When applied for both a capacitively coupled plasma and an inductively coupled plasma, this method provides satisfactory results compared with those measured using a Langmuir probe.

• Open/close Measurements of streamer head potential and conductivity of streamer column in cold nonequilibrium atmospheric plasmas

  A Shashurin et al 2012 Plasma Sources Sci. Technol. 21 034006 Tag this article

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  This work presents a simple method for the characterization of streamers developing in cold atmospheric plasma jets. The method is based upon stopping (‘scattering’) of streamers by means of an external dc potential in order to determine the potential of the streamer head. The experimental evidence presented in this work does not support the model of the electrically insulated streamer head. In fact, it shows that the electrode potential is transferred to the streamer head along the streamer column to which it is attached with no significant voltage drop. Based on the proposed method, we determine various streamer parameters such as head charge ((1–2) × 10 ⁸ electrons), electrical field in the head vicinity (about 100 kV cm ⁻¹), average conductivity (10 ⁻² Ω ⁻¹ cm ⁻¹) and plasma density of the streamer column (2 × 10 ¹³ cm ⁻³).