Alignments of a Microparticle Pair in a Glow Discharge

Stability of a vertically aligned microparticle pair in a stratified glow DC discharge is experimentally investigated. Using laser perturbations, it is shown that, for the same discharge parameters, a pair of microparticles can be suspended in two stable configurations: vertical and horizontal. The interparticle interaction and the electric field of the stratum in the region of particle levitation are quantitatively investigated for the first time. The decharging effect of the lower (downstream) particle by the ion flow wake is also observed for the first time in a glow discharge. The obtained experimental data made it possible to check the analytical criteria for the configurational stability of the system.

Effect of ionization waves on dust chain formation in a DC discharge

An interesting aspect of complex plasma is its ability to self-organize into a variety of structural configurations and undergo transitions between these states. A striking phenomenon is the isotropic-to-string transition observed in electrorheological complex plasma under the influence of a symmetric ion wake field. Such transitions have been investigated using the Plasma Kristall-4 (PK-4) microgravity laboratory on the International Space Station. Recent experiments and numerical simulations have shown that, under PK-4-relevant discharge conditions, the seemingly homogeneous direct current discharge column is highly inhomogeneous, with large axial electric field oscillations associated with ionization waves occurring on microsecond time scales. A multi-scale numerical model of the dust–plasma interactions is employed to investigate the role of the electric field in the charge of individual dust grains, the ion wake field and the order of string-like structures. Results are compared with those for dust strings formed in similar conditions in the PK-4 experiment.

CFD simulation of DC-discharge in airflow

The main purpose of this work is to simulate a dynamics of DC discharge in a subsonic airflow. The calculations were performed in the FlowVision 3.12.01 software package. The single-fluid model (MHD approach) of equilibrium plasma was used while the initial discharge channel was set manually. Cylindrical coaxially arranged electrodes were located in the central part of the calculation area, in the core of the airflow. A 5A DC discharge at atmospheric pressure was considered, as well as a simple model of a re-breakdown between parts of discharge filament. In this work, three-dimensional distributions of temperature and current density were obtained during an evolution of discharge in a flow. Discharge channel extension by the airflow and partial channel decay after the re-breakdown process were shown.

Intensification of mixing of fuel with supersonic air flow when injection and electric discharge are combined

This paper presents the results of experimental investigations of DC discharge influence on mixing intensification of transvers injected gas jet into supersonic aiflow. The air was used as injected gas to prevent the influence of chemical reactions on measurements. The data obtained during discharge includes current and voltage acquisition, registration of pressure pulsations in the jet downstream of discharge operation accompanied by correlation and Fourier analysis allowed to conclude that discharge significantly increase the pressure pulsations in a wide frequency range of 1000 Hz to 50kHz. Increase of the oscillations near the jet boundary is assumed to be related to kinematic mixing intensification of the injected gas with the oncoming flow.

Depth Profile Analysis of the Modified Layer of Poly(vinyltrimethylsilane) Films Treated by Direct-Current Discharge

Previously, we found that modification of the membrane surface from polyvinyltrimethylsilane (PVTMS) by treatment with low-temperature plasma induced by low pressure DC discharge leads to a significant increase in gas separation characteristics. To understand the mechanism of this phenomenon, in this article XPS combined with precision etching 10 keV beam of Ar2500+ clusters was used for depth profiling of PVTMS spin-coated films before and after DC discharge treatment. The etching craters depths were measured by stylus surface profiler. The average etching rate of the untreated PVTMS film by Ar2500+ clusters was defined (230 nm/min). It was found that the low temperature plasma treatment of PVTMS leads to a sharp increase in the oxygen concentration on a surface with a simultaneous decrease in the carbon content. The experimental data obtained indicate also that the treatment of PVTMS film by plasma leads not only to a change in the chemical structure of the surface, but also to the formation of a gradient subsurface layer with a thickness of about 50 nm.

Development of Technology for Vacuum Surface Conditioning by RF Plasma Discharge Combined With DC Discharge

Introduction. It is important to decrease light and heavy impurities influxes towards the plasma volume during the high temperature plasma experiments in fusion devices. This is why the conditioning of the wall inner vacuumsurfaces is a basic part of the fusion device operation.Problem Statement. The conventional inner vacuum chamber surface conditioning methods has a significant drawback: sputtering materials in a vacuum chamber. The inner vacuum surfaces can be also conditioned with radio-frequency (RF) discharge plasma, but the conditioning effectiveness is limited by low ion energy.Purpose. The purpose of this research is to develop vacuum surface conditioning technology by the radio frequency plasma combined with DC discharge. Materials and Methods. The noncontact passive method of optical plasma spectroscopy has been used to estimate ion plasma composition. The stainless steel outgassing has been determined in situ with the thermodesorption probe method. The sputtering of the samples has been measured with the weight loss method.Results. The studies of combined discharge have shown that: the anode voltage of combined discharge is lower than in case of the glow discharge; the stainless steel 12Kh18N10T erosion coefficient is about 1.5 times less in thecase of combined discharge than in the glow one; the thermal desorption diagnostic of wall conditions in the DSM-1 has shown better efficiency with the combined discharge as compared with the glow discharge. Theproposed technology is an original one and has no analogs.Conclusions. The reported research results have shown good prospects for the combined discharge usage for plasma walls conditioning and opportunities for using the combined discharge technology for big fusion machines.