Abstract: A supersonically expanding arc plasma in argon is analyzed both experimentally and theoretically. The plasma is created in a cascaded arc and extracted through a hole in the anode. It emanates in a large vacuum system, where it expands supersonically. This expansion is limited by a shock wave. After the shock wave a subsonic plasma beam is created. A quasi one-dimensional model, based on the conservation of mass, momentum and energy is presented. The shock wave is treated as a discontinuity. The electron density, the gas velocity and the gas temperature are measured as a function of the position in the expansion by means of Stark broadening and Doppler spectroscopy. The model calculations agree well with the measurements, especially in the first part of the supersonic flow.

Abstract: Electron energy distribution functions (eedf) in CO2 laser discharge (He—CO2—N2—CO mixture) have been calculated by solving the Boltzmann equation in the presence of given concentrations of excited (vibrational and electronic) states. The results show a well structured eedf as a result of second kind collisions coming from metastable electronic states of N2 and He as well as a strong dependence of rate coefficients for CO2 dissociation and for the ionization of the different species.

Abstract: In this paper, the various conditions under which the K-dV solitons and double layers may be formed in a plasma that includes two electron-temperatures are examined by deriving a “Further modified K-dV” (FmK-dV) equation in three dimensional space in which there is assumed to be an ambient magnetic field. Structural forms of the various ion-acoustic waves are discussed by obtaining both soliton-specific and double layer-specific solitons of the FmK-dV equation. Particular results are deduced as special cases of the more general cases.

Abstract: In low pressure plasmas the transition between the presheath and the sheath is investigated taking into account solutions of a two-fluid model in the whole plasma. The kinetic theory is reviewed only shortly. The hydrodynamic theory is described in detail. In addition, new results are given. Boundary conditions necessary for the hydrodynamic description are derived from the electron kinetics. The two-fluid equations supplemented by the Poisson equation constitute a set of nonlinear differential equations with isolated singular points. In addition, this is a singularly perturbated problem if the space charge sheath is thin. Singular points occur if the ions or the electrons attain the corresponding sound speed. The mathematical problem can be split into a boundary value problem for subsonic ion velocities and in an initial value problem for the hypersonic range. Solutions are obtained by combination of analytical and numerical methods. The numerical integration involvesinstabilities in the subsonic range if simultaneously the plasma is collision dominated and the space charge density is very small in the interior. Several methods are given to reduce or to avoid these difficulties. It is shown that a magnetic field, directed parallel to the tube wall, can reduce the voltage drop across the sheath substantially. In a positive column the radial variation of the electron temperature is calculated by means of the two-fluid model. Sheath criteria are discussed.

Abstract: In a dc glow discharge in oxygen, the concentrations of minor components of O2(a1Δg), O2(b1 Σg), O3, O(1D), as well as nagative ions and electrons have been measured. Balance equations have been derived which describe satisfactorily the stationary concentrations of these components as functions of gas pressure and discharge current. For the first time, the rate constants of important aeronomical reactions (a) O− + O2(a1Δg) O3 + e, (b) O2− + O2(a1Δg) 2O2 + e and (c) e + O3 O2− +O have been measured as functions of gas temperature T and mean energies of ions Ei and electron E6: Ka = (2.5 ± 0.5) · 10−9 · (T/300)4 ± 0.4· (Ei/0.04)−2.6 ± 0.4 cm3/s for T = 385−605 K and Ei = 0.10 − 0.66 eV; Kb = (1.0 ± 0.3) · 10−10 · (T/300)−2 ± 0.5 · (Ei/0.04)0.23 ± 0.05 cm3/s for T = 330−605 K and Ei = 0.09 + 1.5 eV; Kc for Ee = 0.8÷5 eV.

Abstract: A hydrodynamic description of a low-pressure discharge with singly and doubly-charged positive ions in the high ionization regime is given. Modified hydrodynamic equations are used to include the neutral gas depletion by ionization processes under free-flight conditions. Analytical formulas for the concentrations of the two species of ions at the discharge axis are derived. Numerical results for the radial drift velocities, the radial distributions of the densities and the neutral gas temperature are presented. The nature of the dip in the density profile of the singly-charged ions and the decrease in their radial drift velocity near the axis with increasing degree of ionization are discussed.

Abstract: Low pressure microwave plasmas are of growing interest for plasmachemical applications since they have special and in some cases unique advantages with respect to other plasma excitation methods. Subject of this paper are spatially resolved measurements of the optical emission of a special planar microwave plasma source utilized to investigate different plasmachemical processes. The optical emission spectroscopy (OES) is used as a tool to get information concerning the spatially distribution of reactive atom and molecule concentration by actinometry and concerning the neutral gas temperature by measurements of Doppler line broadening. The results refer to hydrocarbon containing hydrogen plasmas which gas pressures above 100 Pa. Surprisingly measurements confirm an earlier developed simplified two layer model consisting of a preferentially physically active plasma layer near the microwave window followed by a preferentially chemically active decaying region. They give evidence that this model is more adequate to the real physical situation as assumed until now.

Abstract: A method for obtaining a medium pressure (p ∼ 1 torr), low power (< 100 W), RF-generated plasma jet, suitable for chemical kinetics studies and technological applications is described. Though various supply gases can be used to create the plasma jet, only results on the properties of a nitrogen jet are given in this paper with an emphasis on some spectral and electrical characteristics. The emission spectra of the nitrogen jet are discussed and spatial distributions of the relative concentration of nitrogen or radical impurities emitting species such as N2(C3Πu, v' = 0), NH(A3Πg, v'=0) in the bulk of the postdischarge plasma are calculated from the intensity of their vibrational bands. Electrical space resolved double probe measurements and the spatial distributions of the electron density and temperature in the plasma jet are also presented. Possible applications are shortly discussed.

Abstract: The dispersion properties of potential surface waves (SW), propagating at a warm nonisothermal plasma-metal boundary across the external magnetic field are studied in this paper. The existence of potential SW is shown to be possible in frequency ranges, where electromagnetic SW do not exist. The influence of transverse plasma density inhomogeneity on dispersion properties of the SW considered is studied as well.

Abstract: An experimental study of the evolution along the creation process of the plasma parameters characterizing a dc pulsed Argon discharge has been developed. The diagnostic of these parameters is based on the I — V probe characteristic technique. The electron density evolution values so measured are in a good agreement with those obtained from a theoretical model of this process, so the validity of the assumptions involving the model are confirmed.

Abstract: The impact of individual collision processes on the relaxation of the velocity distribution function of a group of electrons, initially localized in a narrow region at relatively high energies, has been studied. By having recourse to solutions of the non-stationary Boltzmann equation and to corresponding Monte-Carlo simulations, the temporal behaviour of electrons in CO2 plasmas, both in the absence and the presence of an external dc field, has been investigated. A microphysical interpretation of observed relaxation phenomena, based on the data relevant to the individual collision processes, is also given.

Abstract: Der vorliegende Artikel befast sich mit dem statischen Starkeffekt bei Feldstarken oberhalb von einigen hundert kV/cm. Im Vordergrund stehen dabei Untersuchungen von nicht wasserstoffahnlichen atomaren Systemen. Nach einer Beschreibung der heute verwendeten apparativen Anordnung zur Realisierung derartiger Felder wird anhand der Ergebnisse von Untersuchungen an Edelgasatomen (vorzugsweise Neon) gezeigt, wie sich auf der Basis umfangreicher experimentell gewonnener Daten allgemein gultige ‘Regeln’ uber die meist sehr komplizierten Verhaltensweisen von Starkeffekt-Niveaus aufstellen lassen. Des weiteren wird gezeigt, wie die gemessenen Verschiebungen uber weite Feldstarkebereiche hin in relativ einfacher Form analytisch beschrieben und dokumentiert werden konnen. Daruberhinaus wird auf das Problem einer brauchbaren Nomenklatur fur die Starkeffekt-Niveaus hin-gewiesen und vorgeschlagen, dafur jeweils einen Satz geeigneter Quantenzahlen zu verwenden. Dies setzt allerdings eine adaquate theoretische Beschreibung der jeweiligen Starkeffektzustande voraus.

Abstract: We present a collisional-radiative model of helium plasma with explicit inclusion of metastable state influences and give results of numerical calculations of population coefficients and effective reaction rates (generalization of effective ionization and recombination coefficients for the case when metastable states are not explicitly included) for a large region of electron densities and temperatures for optically thin and thick helium plasma. The model is described in this paper.

Abstract: A simple theoretical analysis of the discharge characteristics and the laser output performance of a discharge - pumped XeCl-laser is described. Validity of the model is confirmed by comparing the results with the measured time histories of the discharge voltage and current as well as with measured laser-output-energies. The model allows qualitative explanations with respect to the laser output energy in dependence on the total gas pressure, the concentrations of Xe and He as well as the load voltage of the power supply and the primary stored energy.

Abstract: A model is proposed for the formation of the electron energy distribution in a hollow cathode discharge. On the basis of this model, an integral equation has been derived to calculate the electron distribution function over the entire cathode cavity volume. The equation holds true for both the isotropic distribution, and the case when the local distribution function is anisotropic. Solutions of the kinetic equation obtained are presented, for electron energies over 2–3 eV and up to the cathode fall potential. It is shown that the electron energy distribution function in this interval determines the optical characteristics of the hollow cathode discharge. A comparison is given of the calculated and measured radiation powers for the cases of the hollow cathode discharge in xenon and carbon dioxide. The discrepancy between the theoretical and experimental data does not exceed 20%.

Abstract: The work advances a discrete mathematical model of physico-chemical reactions. Possibilities of the described model application for calculation of physico-chemical systems with complicated behaviour are analyzed.

Abstract: On the basis of existing experimental and theoretical results on Stark widths of neutral and multiply ionized states of krypton and xenon, we have indicated existence of certain regularities of Stark broadening for ns-np types of transitions. These regularities were used to estimate the Stark widths of spectral lines from KrIV and XeI spectra that have not yet been measured or calculated.

Abstract: The development of Buneman kinetic instability in plasma with hot electrons and cold ions is investigated in the quasilinear approximation at current velocites close to the instability threshold values. It is shown that the contribution of electron's dielectric permeability in the dispersion equation is negligible and that quasilinear theory has in general stabilizing effect.

Abstract: The influence of high electric fields on the distribution function and following on the dielectric constant is considered in the framework of nonequilibrium Greenfunction technique. In the partial ionized H-plasma additional plasma-poles occur due to the field, which become field dependent. The existence of 2 maxima in the distribution function results in additional damping and turbulent regions.

Abstract: The impact of a secondary electron beam, generated at the electrodes and accelerated in the sheaths, on the self-consistent treatment of the electron behaviour in an rf bulk plasma has been investigated by a parametric study. Source of electrons in the plasma are collisional ionization and secondary electron injection. Electrons are lost by ambipolar diffusion to the electrodes of a parallel plate rf discharge configuration. The non-stationary Boltzmann equation is used to determine self-consistently the rf field amplitude necessary for maintaining the steady-state rf bulk plasma as well as the time resolved behaviour of the electron energy distribution function and of all contributions to the electron particle and power balance, at given source rate and energy distribution of secondary electron injection.

Abstract: Based upon former studies concerning the nonstationary electron kinetics in collision dominated, weakly ionized plasmas the phase delay between the ac electric field component and the resultant ac electron current density has been analysed, theoretically and experimentally, under the specific conditions of a microwave field superimposed to a dc discharge plasma column. The complex plasma conductivity and thus the phase delay has been calculated by solving an appropriate electron kinetic equation. The same quantities have been experimentally determined by using the microwave cavity which operates with different resonator modes. A comprehensive comparison between calculated and measured quantities for different neon discharge plasmas leads to a complete confirmation of the theoretical expectations.

Abstract: The article presents results of probe measurements of the electron and ion densities in an argon rf discharge. The electron density is determined from the electron probe current at the space potential which is estimated by extrapolation of the linear part of the probe electron current dependence to the plasma potential. The plasma potential is calculated from the floating potential. The positive ion density is determined from the probe ion saturated current according to collisional KOPICZYNSKI and ZAKREWSKI model [1]. The agreement between the electron and ion densities is better than in the work of HOPKINS and GRAHAM [2], where the collisionless Lafram-boise theory is used under similar conditions.

Abstract: In a preceding part of the paper, based on the Fourier expansion technique, a new method was developed to study the electron kinetics in weakly ionized, spatially uniform bulk plasmas of rf discharges in the established periodic state. Starting from the electron Boltzmann equation the Fourier expansion technique has been applied to the partial differential equation system for f and fA, the isotropic part and the first contribution to the anisotropy of the electron velocity distribution function, where both the distribution parts are the first two coefficients of the Legendre Polynomial expansion of the distribution function. In this part of the paper the new method will be applied to investigate the behaviour of the electron velocity distribution of the rf bulk plasma in molecular hydrogen and, in addition, of main macroscopic quantities. The study of the latter quantities will be possible since these are determined by appropriate energy space averaging over f and ft, respectively. Thus, a comprehensive harmonics analysis of the electron component of the rf H2 bulk plasma could be made in a wide rf field frequency range. This includes the determination of the harmonics contributions to the isotropic and anisotropic distribution and to relevant macroscopic quantities as dependent on the field frequency for the mentioned wide rf field frequency range as well as of the phase angles between the different harmonics. It could be proved that the so-called 10-term approximation is sufficient for the description. Further on the periodic alteration of important macroscopic quantities, as mean electron energy, power input from the rf field and power loss in collision processes etc., and their period averages will be investigated in this truncation order. The results obtained are discussed and could be especially interpreted within a physical concept based on a comparison of the rf field frequency with the lumped collision frequency for energy dissipation and that for impulse dissipation.

Abstract: Evaporation of emitter material from electrodes of fluorescent lamps has been measured by means of atomic absorption of Ba. A hollow-cathode discharge lamp served as background radiator. The arrangement is briefly described. Spot resolved measurements has been done in preheating and in discharge regimes. Essential results are dependence on evaporation rate and filament structure, evaporation and arising of cathode spot in discharge, and diminished evaporation regarding preheating.

Abstract: By using the reductive perturbation technique, the soliton solution of an ion-acoustic wave radially ingoing in a spherically bounded plasma consisting of ions and ion-beams with multiple electron temperatures is obtained. In sequel to the earlier investigations, the solitary waves are studied as usual through the derivation of a modified Korteweg-de Vries (K-dV) equation in different plasma models arising due to the variation of the isothermality of the plasmas. The characteristics of the solitons are finally compared with those of the planar and the cylindrical solitons.