Formation of ArCl(B) molecules in a transverse volume discharge

Results of optimizing a λ=175 nm ArCl(B-X) emitter pumped by a transverse volume discharge are presented. The formation of ArCl(B) molecules was investigated in a plasma formed by mixtures of rare gases with HCl and Cl₂ molecules. It is shown that the Cl₂ molecule is the most efficient chlorine carrier and that neon at pressures ≥ 50 kPa is the most efficient buffer gas. Pis’ma Zh. Tekh. Fiz. 25, 29–33 (June 12, 1999)     

Investigation of the processes of periodic plasma structure formation in transverse nanosecond discharge with a slotted cathode

A periodic standing-like plasmic striation in inert gases has been observed and investigated under transversal nanosecond electric discharges. The pressure limits relevant for formation of a periodic plasma structure have been established, and the critical values for the voltage amplitude and discharge current have been found corresponding to the upper boundary of the range in which the plasma structure is formed. The external magnetic field effect on the parameters of the periodic plasma structure has been studied. It is stated that the plasma structure is formed at the stage of steady-state discharge and that the lifetime of the periodic structure considerably increases when the transversal magnetic field is applied.     

Dynamics of the formation of pulsed transverse nanosecond discharge with prolate slot-cathode

Experimental studies of the spatial-time dynamics in formation and evolution of nanosecond plasma-beam discharge with a prolate slot-cathode in inert gases is investigated using a high-speed camera. Features and regularities in the dynamics of evolution of nanosecond discharge with the slot-cathode are established depending on the external conditions. As it has been shown experimentally, the first registered optical radiation of the discharge arises near cathode surface and the discharge formation starts simultaneously at the cathode slit output and between the electrodes.     

Investigation of the degradation of silane molecules in a pulsed volume discharge

Results are presented of an investigation of the electrical and optical characteristics of a pulsed transverse discharge ignited in a 54×2.0×0.7 cm volume of an Ar+4%SiH₄ mixture. Studies were made of general spectra of the plasma radiation and the temporal and service-life characteristics of the radiation from the degradation products of the silane molecules. This type of discharge is of interest for obtaining porous silicon coatings over large areas. Pis’ma Zh. Tekh. Fiz. 24, 35–39 (November 12, 1998)     

Use of a transverse nanosecond discharge at the prebreakdown electron ionization multiplication stage for selective excitation of neon atoms

An investigation is made of the characteristics of a transverse nanosecond discharge in Ne/SF₆ and He/Ne/SF₆ mixtures at the prebreakdown electron ionization multiplication stage. The conditions needed to obtain a stable transverse discharge with ultraviolet spark preionization are studied as well as the spectral and temporal characteristics of the plasma radiation. It is shown that this transverse discharge burning regime may be promising for the selective excitation of neon atoms which may be used to develop an electric-discharge, λ=585.3 nm, Ne(3s–3p) plasma laser. Pis’ma Zh. Tekh. Fiz. 24, 85–90 (January 12, 1998)     

Reconstruction of the X-ray emission spectrum of a nanosecond creeping discharge

A method is proposed for determining the soft x-ray emission spectrum of a nanosecond creeping discharge. The method includes a determination of the photoelectron density from photocurrent measurements and a calculation of the spectral flux density. The results are compared with experimental data on the wavelength interval of maximum radiation intensity. Pis’ma Zh. Tekh. Fiz. 24, 39–44 (April 12, 1998)     

Periodic plasma structures in nanosecond discharge with a slit cathode

The spatial structure of optical emission from a transverse nanosecond pulsed electric discharge with a hollow (slit) cathode has been experimentally studied. A regular periodic plasma structure has been observed during nanosecond pulsed discharge in helium at medium pressures. Conditions of the plasma structure formation with respect to the discharge voltage and current are determined. It is shown that the observed plasma structure differs from the known types of striations.     

Special features of mechanisms of formation of transverse nanosecond discharge with slot cathode, confined by dielectric walls

Experiments are performed and comparison is made of the electrical and optical characteristics of open and confined transverse nanosecond discharges with a slot cathode. It is found that the duration and shape of current pulse under conditions of open and confined discharges are significantly different and, under some conditions, the current density of confined discharge exceeds that of open discharge by more than an order of magnitude. Estimates are obtained of the coefficient of electron emission from cathode plasma, which significantly exceed the coefficient of electron emission in an abnormal discharge. It is demonstrated that the beam mode of primary electrons in the cathode layer during motion in the anode direction gradually transforms to hydrodynamic mode. The free paths of accelerated electrons in plasma are determined, and it is demonstrated that they reach the anode and have a significant impact on the dynamics of development and on the structure of optical radiation of transverse nanosecond discharge with a slot cathode.     

Studying transverse volume discharge in a helium-propane mixture

The electrical properties and emission characteristics of plasma formed in a transverse volume discharge in helium-propane (He-C₆H₁₄) mixtures at a total pressure of 3–15 kPa have been studied. The spatial parameters, plasma emission spectra, and current and voltage oscillograms of the discharge, as well as the yield of carbon-containing products of propane decomposition at various pressures and compositions of the He-C₆H₁₄ gas mixture, have been determined.     

Characteristics of a submicrosecond transverse discharge in mixtures of helium with N2 and CO molecules and xenon atoms

An investigation is made of the electrical and optical characteristics of a moderate-pressure transverse discharge in typical active media of infrared CO lasers. The discharge was ignited in a system of unprofiled “ grid-plane” electrodes with automatic ultraviolet preionization by a corona discharge and had a 2×3 cm aperture. The pulse repetition frequency was 1–10 Hz, the current pulse length was ≤0.5 μs, and the pressure of the working mixtures was 10–100 kPa. Studies were made of the transverse discharge current voltage pulses, and also the spectral and temporal characteristics of the plasma radiation in N₂:CO, He:N₂:CO, and He: N₂:CO:Xe mixtures in the ultraviolet and visible ranges. Pis’ma Zh. Tekh. Fiz. 23, 71–76 (October 12, 1997)     

Radiative characteristics of a nanosecond discharge in water with aluminum based electrodes

The results of experimental investigation of the electrical and optical characteristics of a pulsed periodic nanosecond discharge in distilled water with aluminum and duralumin electrodes are given. Oscillograms of the current and voltage on the electrodes of the discharge are presented; the pulse power and the specific energy contribution from the discharge to the plasma have been calculated. In the spectra obtained, lines of aluminum, copper, hydrogen, and oxygen have been observed against the background of continuous emission in the visible range.     

A positive column of electric discharge in a transverse magnetic field

The influence of a transverse magnetic field on the characteristics of the positive column of electric discharge was investigated in both the diffusion and nondiffusion approximations. All solutions in the diffusion approximation were derived in analytical form. It is shown that with the enhancement of the magnetic field induction, the concentration distributions of the plasma and particle fluxes to insulated walls become nonsymmetric, the concentration maximum displaces in the direction of the magnetic force action, and the ion flux concurrent with this force may exceed substantially the ion flux in the opposite direction. The dependences of discharge parameters on the induction value are defined for helium. It is demonstrated that there is a maximum value of induction which bounds from above the range of magnetic fields, where the stationary state of the positive column is possible. In the range allowed for the stationary state, a single induction value is matched by two different modes of the positive column varying in values of the electron energy, drift speed, and electric-field strength. By means of the transverse magnetic field, it is possible to vary the electron energy within wide limits (from a few electronvolts to several hundred electronvolts).     

Transport properties of Freon-152a and Freon-142b in the temperature range of 280–510 K

The thermal conductivity of 1,1 difluoroethane (Freon-152a) and 1 chloro-1 difluoroethane (Freon-142b) are measured at several pressures in the range 29.7–75.8 kPa and as a function of temperature in the range 280–510 K. The thermal conductivity column instrument is employed, and the experimental values are estimated to be accurate within a maximum uncertainty of ±5.6% at the lowest temperature, which reduces to ±2.4% at the highest temperature. These conductivity values are compared with the predictions of Chapman-Enskog kinetic theory, with the correction factor for the internal energy transport estimated from Hirschfelder's theory, and the Lennard-Jones (12-6) potential. The experimental conductivity data are also utilized to generate the values for the two other transport properties in conjunction with the interrelations obtained between different properties on the basis of kinetic theory. The data on transport properties are employed to give the best possible estimates of Prandtl and Schmidt numbers as a function of temperature.     

The formation of diffuse discharge by short-front nanosecond voltage pulses and the modification of dielectrics in this discharge

The dynamics of diffuse discharge formation under the action of nanosecond voltage pulses with short fronts (below 1 ns) in the absence of a source of additional preionization and the influence of a dielectric film on this process have been studied. It is established that the diffuse discharge is induced by the avalanche multiplication of charge initiated by high-energy electrons and then maintained due to secondary breakdowns propagating via ionized gas channels. If a dielectric film (polyethylene, Lavsan, etc.) is placed on the anode, then multiply repeated discharge will lead to surface and bulk modification of the film material. Discharge-treated polyethylene film exhibits a change in the optical absorption spectrum in the near-IR range.     

Glow discharge in a transverse supersonic gas flow at low pressures

A low-pressure glow discharge in a transverse supersonic gas flow was experimentally studied for the case where the flow only partially fills the interelectrode gap. It is shown that the space region with supersonic gas flow has a higher concentration of gas particles and, therefore, works as a charged particle generator. The near-electrode regions of glow discharge are concentrated specifically in this region. This structure of glow discharge is promising for plasma deposition of coatings under ultralow pressures.     

An experimental study of heat transfer in the boiling of Freon-12 in a field acted on by centrifugal forces

Results are described for an investigation into the boiling of Freon-12 in the following range of inertial accelerations:a/g=1–5250.     

Investigation of liquid-vapor interface vibrations during film boiling of Freon-113 on a spherical surface

Experimental investigation of saturated Freon-113 film boiling on a sphere with 30 mm diameter at atmospheric pressure under conditions of free convection was carried out. Nonsinusoidal wave formations at the liquid-vapor interface were revealed using high-speed video recording. The temperature gradient dependence for the average vapor film thickness was determined.     

The formation of excited chlorine atoms in a low-pressure transverse volume discharge

The characteristics of a transverse volume discharge (TVD) in chlorine at low pressures (P(Cl₂)=0.1–1.5 kPa) were studied. The excited chlorine atoms were formed in a 18×2.2× (0.5–1.0) cm volume using relatively low values of the capacitor bank charging voltage (U _ch ≤ 10 kV) in the pulsed discharge voltage source. The optical emission from plasma was studied in a spectral range from 500 to 900 nm. Homogeneous TVD pulses of short duration (τ; ≤ 100 ns) obtained under these conditions are of interest for use in UV-VUV lamps employed in pulsed plasmachemical reactors for dry etching of thin films. The density of excited atomic chlorine radicals can be monitored on medium-resolution spectrometers using the ClI emission lines with λ=725, 754, and 821 (2) nm.     

Measuring parameters of volume nanosecond pulsed discharge in air at atmospheric pressure

We report on the basic electrical characteristics of the volume nanosecond pulsed discharges in air at atmospheric pressure. The measurements of temperature were performed using spectral methods, whereas the electron density of plasma was measured using a multibeam Fabry-Perot interferometer. It is shown that, subject to maintaining the form of the volume discharge, the maximum electron density is 1.5 × 10¹³ cm^?3, which is comparable to the critical value in streamer discharges.     

Real-time decay of fluorinated fullerene molecules on Cu(001) surface controlled by initial coverage

Nano Research - In this study, the evolution of C60F18 molecules on a Cu(001) surface was studied by means of scanning tunneling microscopy and density functional theory calculations. The results...