Equation of state for a weakly ionized gas-discharge plasma

A modification is proposed for the van der Waals equation for a real gas, which transforms it into an equation of state for a thermally nonequilibrium weakly ionized gas-discharge plasma. This modification reflects the existence of collective interactions between neutral particles in the gas-discharge plasma, which generates quasistructural formations impeding the compression and expansion of the plasma. This equation completely describes the characteristics of the dynamic processes in the gas-discharge plasma, provides a quantitative explanation of these processes, and reveals the essential physical features of this phenomenon. Pis’ma Zh. Tekh. Fiz. 23, 81–88 (July 26, 1997)     

Transport of microparticles in weakly ionized gas-discharge plasmas under microgravity

Effective structural (pair correlation function) and transport (diffusion constant) characteristics of the system of microparticles (dusty plasma) have been measured in a set of experiments in dc- and rf gasdischarge plasmas in ground-based and microgravity conditions on the board of Russian “Mir” Space Station and International Space Station. The comparison between these measurements and numerical simulations were used for dusty plasma diagnostics. Specifically, the effective coupling parameter, which mainly governs structural and dynamical properties of the system, was determined for different experimental conditions. The application of these measurements to estimate the particle charge and the plasma screening length is discussed.     

Charge kinetics in weakly ionized plasma of electronegative gases

This work is devoted to investigation of specific features for processes of ionization and recombination in a weakly ionized plasma of electronegative gases in an external electric field in the presence of ion-molecular reactions. By analogy with the problem of the shift of the energy level of the ground state of the quantum-mechanical Fermi system, a simple analytic expression for the calculation of the effective ionization rate under these conditions was found. For the first time, a criterion of the dielectric strength for electronegative gases, which takes into account all the ion-molecular reactions with the participation of negative ions, is formulated. The recombination process in the ion plasma of electronegative gases is considered both in the presence of and without these reactions. Cases permitting the analytic solution of a set of differential balance equation for components of the decaying ion plasma are selected.     

Shock waves in a gas-discharge plasma

We experimentally determine the dynamic characteristics, and also the parameters (concentration and temperature of the electrons) and the ionic composition of a plasma before and behind the front of a shock wave which is propagating in the gas-discharge plasma. We show that during shock wave propagation in a nitrogen plasma in the initial stages of the discharge, the shock wave is accelerated and amplified, because of the release behind the shock wave front of energy stored in the gas discharge.T. G. Shevchenko State University, Kiev. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 62, No. 5, pp. 707–713, 1992.     

Emission characteristics of gas-discharge ethanol-vapor plasma

Emission characteristics of a low-temperature ethanol-vapor plasma formed with the use of high-frequency and barrier discharges have been studied. The plasma emission in the spectral range of 300–700 nm was analyzed in detail. The partial pressure of the ethanol vapor was 5.7 kPa. The emission spectra of the ethanol- and argon/ethanol-vapor plasmas strongly differ. In addition, time characteristics of current and emission pulses in a high-frequency discharge in ethanol vapor are presented.     

Destruction of Bacillus stearothermophilus bacteria by weakly ionized low pressure cold oxygen plasma

High resolution scanning electron microscopy (SEM) has been applied to study degradation of Bacillus stearothermophilus bacteria upon exposure to oxygen plasma. Bacteria were grown according to standard prescribed protocol, carefully rinsed with distilled water and deposited onto well polished silicon wafers. The wafers were exposed to oxygen plasma and then characterized by SEM. Plasma was created in an electrode-less RF discharge in the E mode. Plasma parameters were determined with a double Langmuir probe and a catalytic probe. At the working pressure of 75 Pa, the electron temperature was about 3 eV, plasma density about 6 × 10¹⁵ m⁻³ and the density of neutral oxygen atoms about 4 × 10²⁰ m⁻³. SEM investigation revealed slow degradation of the bacterial capsule, which was accomplished in several seconds of plasma treatment. Further exposure to plasma resulted in etching of the bacterial cell wall which was totally destroyed in about half a minute. The remains of the organic material were then slowly oxidized until only ash remained after few minutes of plasma treatment. The organic material degradation was predominantly due to oxidation with O atoms. The dose of atoms needed for damaging of the cell wall was estimated to about 2 × 10²⁴ m⁻² while full degradation was observed after receiving the dose of 5 × 10²⁴ O atoms/m².     

Characteristic features of low-temperature gas-discharge plasma flows

An investigation is made of the nature of gasdynamic anomalies accompanying the motion of shock waves and objects in a low-temperature nonequilibrium plasma. It is shown that these anomalies are caused by characteristic features of sound propagation in the plasma. Pis’ma Zh. Tekh. Fiz. 23, 88–93 (August 26, 1997)     

Radiation from electrically short antenna in a limited volume of gas-discharge plasma

It is established that the electric field strength of an electrically short (l/λ ? 10^?3) transmitting antenna exhibits an increase by a factor of more than 10² when it is placed into a vacuum tube featuring a continuous dc discharge. The influence of an external magnetic field on this phenomenon is studied as well.     

Highly repetitive, extreme-ultraviolet radiation source based on a gas-discharge plasma.

An extreme-ultraviolet (EUV) radiation source near the 13-nm wavelength generated in a small (1.1 J) pinch plasma is presented. The ignition of the plasma occurs in a pseudosparklike electrode geometry, which allows for omitting a switch between the storage capacity and the electrode system and for low inductive coupling of the electrically stored energy to the plasma. Thus energies of only a few joules are sufficient to create current pulses in the range of several kiloamperes, which lead to a compression and a heating of the plasmas to electron densities of more than 10(17) cm(-3) and temperatures of several tens of electron volts, which is necessary for emission in the EUV range. As an example, the emission spectrum of an oxygen plasma in the 11-18-nm range is presented. Transitions of beryllium- and lithium-like oxygen ions can be identified. Current waveform and time-resolved measurements of the EUV emission are discussed. In initial experiments a repetitive operation at nearly 0.2 kHz could be demonstrated. Additionally, the broadband emission of a xenon plasma generated in a 2.2-J discharge is presented.     

Zinc oxide molecules and clusters formed in a quasiclosed volume of reactive gas-discharge plasma

Plasma-deposited zinc oxide films were studied and it was established that oxide molecules may form and their clusters nucleate within a recombination burning zone in the volume of plasma, provided that the ion range does not exceed the size of a discharge chamber. The nucleation zone is rather narrow and its position depends on the gas pressure in the chamber. The zinc oxide films grown in this zone possess a texture with small misorientation angle and are characterized by small thickness of the nucleation texture and high piezoelectric activity.     

电去离子净水设备脱除弱电解质的机理及能力

电去离子(EDI)净水设备能否从其进水中彻底除去弱电解质,是使用EDI净水设备所碰到的关键问题.文章提出了EDI净水设备脱盐能力的概念,并给出估算脱盐能力的经验公式,可用它作为衡量EDI净水设备正常工作的判据.讨论了EDI净水设备脱除弱电解质的机理和能力,及与脱除强电解质的区别,同时,还用提出的电去离子过程的反应叠加模型,通过离子交换层谱给以形象化的解释.     

Megawatt low-temperature DC plasma generator with divergent channels of gas-discharge tract

We have developed and studied a new effective megawatt double-unit generator of low-temperature argon plasma, which belongs to the class of dc plasmatrons and comprises the cathode and anode units with divergent gas-discharge channels. The generator has an efficiency of about 80–85% and ensures a long working life at operating currents up to 4000 A.     

Gas temperature measurements in weakly ionized glow discharges with filtered Rayleigh scattering

We report the first gas temperature measurements in plasmas to our knowledge obtained by filtered Rayleigh scattering (FRS). A narrow-linewidth Ti:sapphire laser is used as the illumination source, and a mercury filter provides strong suppression of elastic background. We perform measurements in weakly ionized glow discharges in pure argon and in an argon-plus-1%-nitrogen mixture. Where possible, we verify the FRS technique by comparing filtered measurements with unfiltered measurements. We present point measurements of axial temperature with uncertainties of less than 5%. We use a planar scheme to obtain radial temperature profiles with uncertainties of 10%.     

Conversion of air mixture with ethanol and water vapors in nonequilibrium gas-discharge plasma

In search for an alternative fuel for internal combustion engines, we have studied the possibility of obtaining molecular hydrogen via the conversion of air mixture with ethanol and water vapors in a new plasma reactor. It is shown that, in agreement with experimental data, the H₂ concentration is a linear function of the discharge current and decreases with increasing gas flow rate in the interelectrode gap. It is established that the proposed approach provides higher molecular hydrogen concentrations as compared to those achieved with other methods.     

Exact solution of nonlinear equations describing stationary ionization wave profile in gas-discharge plasma

An exact solution is obtained for the system of nonlinear equations describing a stationary ionization wave profile in inert gas-discharge plasma.     

Nonequilibrium state of highly ionized helium plasma at atmospheric pressure

A spectral study of arc helium plasma of atmospheric pressure with the electron density n _e ≤ 10¹⁷ cm^?3 and the ionization degree of ～0.25 is performed. The character of the population of HeI levels with the excitation energy of 20.96–24.04 eV, which indicates infeasibility of the Boltzmann law with the electron temperature T _e for describing the relative population of excited HeI states, is experimentally determined. Due to the experimentally revealed unfitness of the local thermodynamic equilibrium (LTE) model for estimating T _e , mixed contours of the HeI 1083 line were divided into the Lorentz and Gaussian components. As a result, both the Stark effect constant that is poorly studied for this line and the temperature of heavy particles T _g in the plasma were estimated based on the Doppler component of its Gaussian half-width. As the arc current varied from 200 to 400 A, T _g increased from 20000 to 25 500 K, while the increase in the ionization temperature was, in this case, negligible (from 20000 to 21000 K).