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This work is devoted to the investigation of physical processes in a non-equilibrium plasma of a binary mixture of inert gases. The degree of radial separation of the mixture was found to increase with increasing pressure of buffer gas and discharge current and to decrease with growing partial pressure of the admixture. The correlation of the radial and axial types of separation was shown experimentally. The kinetics of population of the metastable states He(2³S) and Xe(³P2₂) and of charged particles was investigated using an impulse regime. The time for the establishment of the stationary state of the radial distribution of the components was found to be several times less than the time of reestablishment of the homogeneous distribution of the atomic component after switching off the discharge impulse. The phenomenon of a decreasing effective diffusion length of the discharge was found. This effect has essential influence on the time for the establishment of the stationary state of radial cataphoresis.     

Positive column of a glow discharge in a ternary mixture

The positive column of a glow discharge in a ternary mixture is considered. It is assumed that there is a primary gas, to which are added two gases (vapors) which are completely responsible for the ionization processes. The primary gas serves as a background determining such characteristics as the mobility and the diffusion coefficient of the atoms, ions, and electrons. The axial ion current in the discharge leads to an axial redistribution of the impurity atoms. This phenomenon, called cataphoresis, was considered first in [1] for a binary mixture. In the present paper axial cataphoresis is considered in a ternary mixture.     

Millimeterwave spectroscopy of transient molecules produced in a DC discharge

The construction of a millimeterwave spectrometer to study the pure rotational spectra of transient molecules in the gas phase is presented. The spectrometer is a source-modulated system combined with a free space glass discharge cell. Millimeterwave radiation has been produced using a frequency multiplier, the fundamental radiation source being klystrons. The spectrometer has been used to study the millimeterwave spectrum of carbon monosulfide (CS) and fluorine cyanide (FCN) produced inside the cell in a low pressure DC discharge of precursor gases. The quadrupole hyperfine structures of³³S and¹⁴N nucleus of CS and FCN have been resolved, measured and analysed.     

Cold-hollow-cathode arc discharge in crossed electric and magnetic fields

A crossed-field cold-hollow-cathode arc is stable at low working gas pressures of 10⁻²–10⁻¹ Pa, magnetic-field-and gas-dependent arcing voltages of 20–50 V, and discharge currents of 20–200 A. This is because electrons come from a cathode spot produced on the inner cathode surface by a discharge over the dielectric surface. The magnetic field influences the arcing voltage and discharge current most significantly. When the plasma conductivity in the cathode region decreases in the electric field direction, the magnetic field increases, causing the discharge current to decline and the discharge voltage to rise. The discharge is quenched when a critical magnetic field depending on the type of gas is reached. Because of the absence of heated elements, the hollow cathode remains efficient for long when an arc is initiated in both inert and chemically active gases.     

Lokale Diagnostik einer Argon-Niederdruckentladung mit Hilfe der resonanten Laserstreuung

We report on the experimental investigations on a laser-like low pressure argon gas discharge. The discharge parameters varied in the range from 0,05 to 1 Torr for the gas pressure and from 10 to 30 A for the discharge current. Local electron densities and temperatures have been measured with an adjustable spherical probe. Spatially resolved measurements of the temperatures and drift velocities of the Ar⁺-ions in the radial and axial direction of the positive column have been carried out by the resonant laser light scattering (fluorescence technique). The radial density profiles of the excited Ar⁺-ions have been determined in two different ways and have been compared with the calculations based on a simple collisional radiative model.     

Measurements of the Cathode Fall Characteristics in an Electron Beam Ionized Discharge

Measurements of cathode fall characteristics and of the influence of the cathode fall on the discharge properties of an electron beam ionized discharge (EBD) are reported. Gases investigated included methane, nitrogen, and argon. The cathode fall voltage was found to be a function of discharge current, voltage, gas type and pressure, and the rate of external ionization. At low discharge voltages, the cathode sheath region was found to require microseconds to get established. Added attaching gases had little influence on the cathode fall. Extrapolating to high rates of external ionization, the cathode fall voltage still can be expected to be hundreds of volts for the gases investigated.     

On the ion drift in gas mixtures

The features of the velocity distribution function of ions during their drift in a mixture of different gases are analyzed. Examples of drift of heavy ions in light gas, a mixture of two gases with equal concentrations, and drift of light ions in heavy gas are considered. It was shown that the transition to discharge in mixtures of different gases allows the formation of an ion flux with characteristics unattainable for discharge in single-component gas under typical conditions under which experiments with dust structures in plasma are performed.     

Emission characteristics of plasma of a transverse volume discharge in mixtures of helium, argon, and krypton with sulfur hexafluoride

The emission characteristics of the plasma of repetitively pulsed spontaneous UV-VUV radiation sources on the basis of ArF* (193 nm) and KrF* (249 nm) molecules, and the products of decomposition of sulfur hexafluoride molecules pumped by a transverse volume discharge in a mixture of inert gases with sulfur hexafluoride molecules have been investigated. The discharge emission spectra in the range of 190–780 nm at the low-current and high-current stages of the transverse discharge, the time characteristics of the voltage across the electrodes, the pump current, and the emission of excimer molecules and the products of decomposition of sulfur hexafluoride have been studied. It is shown that, in the gas-static operation mode of the radiator at the number of discharge pulses smaller than 10³, the 193-nm ArF* and 249-nm KrF* bands are main in the emission spectrum. Upon further operation of the radiator, a spectral continuum is formed on the basis of sulfur molecular bands in the range 260–550 nm.     

Two types of spherical stratified gas discharge

Results on experimental investigation of a volume low-pressure gas discharge between the walls of a metal chamber and the small anode in the center of the chamber are represented. The discharge current-voltage characteristics in the range of currents corresponding to Townsend and glow discharges are measured. The experiments were carried out in nitrogen, argon, helium, carbon dioxide, and argon-acetone mixture. Hysteresis of current voltage characteristics is observed for some gas media in the link area of Townsend and glow discharges. It is found that the Townsend spherical discharge plasma is always stratified. Contrary to the glow discharge, stratification in this case is observed in all gases and remains for an arbitrary length of time.     

Excessive hydrogen and deuterium Balmer lines broadening in a hollow cathode glow discharges

Results of a Doppler spectroscopy study of hydrogen and deuterium Balmer lines in the stainless steel and copper hollow cathode glow discharge, operated in pure hydrogen, deuterium and mixtures of inert gases with hydrogen, are reported. For all gases and gas mixtures plasma observations perpendicular to electric field revealed the excessively large Doppler broadening. By changing mode of glow discharge operation, the Doppler broadened line profiles in helium-hydrogen mixture are recorded parallel to the discharge electric field as well. The excessively broadened part of the H line profile is shifted towards blue or red wavelength by changing the direction of electric field vector. The presence of large excessive Balmer lines broadening in pure hydrogen and in its gas mixture with neon as well as shifting of the excessively broadened part of line profile by means of electric field is in contradiction with the resonance transfer model proposed by Mills et al. in several publications, see e.g. [IEEE Trans. Plasma Sci. 31, 338 (2003)].     

Emission anomalous optical magnetic resonances in a mixture of even neon isotopes

Unusual resonances have been detected in the dependence of the discharge glow in neon on the longitudinal magnetic field. The resonances appear in fairly high magnetic fields and are observed only at low gas pressures and exclusively in a mixture of ²⁰Ne and ²²Ne isotopes. This phenomenon is an evidence of collective resonant radiation processes involving atoms of different neon isotopes.     

Simulation of the positive column of a glow discharge in an inert gas-chorine mixture with allowance for the dissociation of chlorine molecules

A model is developed that makes it possible to calculate the concentration of excimer molecules, halogenides of inert gases, in the positive column of a glow discharge initiated in a chlorine-containing gas mixture. Using this model, one can quantitatively reproduce experimental dependences of the excimer UV power on the discharge current in wide ranges of the gas mixture compositions and pressures, provide satisfactory quantitative agreement between calculated and experimental radial distributions of the electron and excimer molecule concentrations, and give a physical explanation for the experimental dependences. To this end, this model, unlike other available ones, allows for the electron-impact dissociation of chlorine molecules, the radial nonuniformity of dissociation, and the radial nonuniformity of the gas temperature.     

Calculation of the He-Cd dc discharge

Numerical evaluations of the excited atom densities and the volt-ampere characteristics in He-Cd dc mixture discharge in a cylindrical tube are reported. For this purpose, under non-equilibrium conditions in low current and low pressure discharge, a set of coupled rate equations for the number densities of atoms in most important quantum states is solved. A model of Cd-and He-atom possessing six and four levels, respectively, is assumed. The results of the computation are given as a function of the external positive column parameters at relative cadmium concentration 10^–3.     

Simulation of gas-discharge UV sources based on a glow discharge in a xenon-chlorine mixture

A model is developed that makes it possible to calculate the concentration of excimer molecules, halogenides of inert gases, in the positive column of a glow discharge initiated in a chlorine-containing gas mixture. Using this model, one can quantitatively reproduce experimental dependences of the excimer UV power on the discharge current in wide ranges of the gas mixture compositions and pressures, provide satisfactory quantitative agreement between calculated and experimental radial distributions of the electron and excimer molecule concentrations, and give a physical explanation for the experimental dependences. To this end, this model, unlike other available ones, allows for the electron-impact dissociation of chlorine molecules, the radial nonuniformity of dissociation, and the radial nonuniformity of the gas temperature.     

Composition dependence of the viscosity of dense gas mixtures

We present a method for the computation of the composition dependence of the viscosity of a dense gas mixture. This method uses the (modified) Enskog theory formula for the viscosity of a dense mixture of rigid-sphere gases, as obtained by Thorne, and assumes that this formula can be applied to real gas mixtures provided one replaces the purely rigid sphere quantities in the Enskog theory by suitably chosen real gas quantities. In order to compute the composition dependence of a mixture one needs: (a) the viscosities of the pure component gases at the same molar density as the mixture; (b) the low-density viscosities of the pure component gases; (c) one low-density value of the mixture viscosity; (d) the second virial coefficient and its temperature derivative for each component pure gas; and (e) in some cases, the equations of state of the pure components. No dense mixture data are required. Many of the low-density and equation-of-state quantities can be obtained with sufficient accuracy from existing correlation schemes. The technique has been applied to three binary systems for which accurate measurements exist: He-Ar, Ne-Ar, and H₂-CH₄. There is agreement to about 1% up to densities 0.7 of the critical, and to about 5% for densities up to 1.8 times the critical for H₂-CH₄. The multicomponent generalization is also given but experimental data for comparison are lacking.     

Luminescence of XeCl* and XeBr* exciplex molecules initiated by a longitudinal pulsed discharge in a three-component mixture of Xe with CsCl and CsBr vapors

The excitation of simultaneous luminescence of XeCl* and XeBr* exciplex molecules in a longitudinal pulsed-periodic discharge has been studied. To generate exciplex molecules, a three-component mixture of xenon with cesium bromide and chloride vapors was used. Spectral, energetic, and pulse-temporal characteristics of the discharge have been investigated, and the dependences of the UV luminescence yield on the composition and excitation conditions of the mixture have been studied. The average specific power of the discharge UV radiation in the Xe-CsBr-CsCl mixture has been determined to be 0.25 W/cm³, which corresponds to the total efficiency value ～0.7%. Also, mechanisms by which exciplex molecules are formed in a low-pressure vapor-gas mixture of the inert gas with halogenides of alkali metals have been considered.     

Isotopic thermal diffusion factors of the noble gases

A new set of isotopic thermal diffusion factors for Ar, Kr and Xe is reported. The data have been obtained from thermal diffusion column measurements in a column previously calibrated with Ne gas, and complete the α_T data for the binary mixtures of noble gases given previously. The results lead to the conclusion that the thermal diffusion properties of the noble gases and their mixtures are well described by the law of corresponding states first proposed by Kestin, Ro and Wakeham. It is also concluded that the calibration technique used makes the thermal diffusion column a valuable instrument for the determination of the thermal diffusion factors of isotopic and non-isotopic dilute gas mixtures.     

Plasma-dust structures in He-Ar DC glow discharge

The gas mixture discharge has a number of features which can appear in experiments with dusty plasma. For example, in the case of a significant difference in atomic masses of ions and atoms, strong anisotropy of the distribution function over ion velocities takes place, which in turn can cause a significant change in properties of dust structures. In this work, experiments on the study of the dust structures in the gas discharge of a mixture of light and heavy gases, i.e., helium and argon, are analyzed. The results of numerical simulation of ion and electron drift in the mixture of these gases and dust particle charging processes are presented.     

Output parameters and a spectral study of UV Cu Ne–CuBr laser

A comparative study on the temporal behaviour of the average output power of UV Cu⁺ laser with quartz and ceramic inserts is reported. Spectral investigations of the discharge are also made. The use of quartz inserts leads to some impurities introduction into the gas mixture and to an average output power reduction from 500 to 30 mW at multiline output (248.6, 252.9, 260.0 and 270.3 nm) for UV lasing of 25 h. The utilization of ceramic inserts allows to maintain relatively constant gas mixture composition and average output power of about 300 mW for 100-h.