High Current Gas Discharge Research Articles

Получение TiN-покрытий реактивным анодным испарением титана в разряде с самонакаливаемым полым катодом

A method for TiN-coatings deposition by anodic evaporation of titanium in a high-current gas discharge (30 A) with a self–heated hollow cathode in an Ar+N2 medium is proposed. Optical spectral analysis shows that a large amount of activated titanium is present in the gas-discharge plasma, and the proportion of metal ions coming from the plasma to the substrate, taking into account the single-charge ions, reaches 70%. At a nitrogen flow of 5 sccm, TiN-coatings with a thickness of 2 µm and a hardness of up to 24 GPa were obtained. The deposition rate at a distance of 7 cm from the vapor source was ~4 µm/h.

High-current gas discharge with a water-solution cathode as a source of plasma flow for gasification of carbon-containing waste

A gas discharge with a water-solution cathode was experimentally studied in the current range 10–25 A. A bulk plasma was obtained in an extended (up to 20 cm) discharge gap. The choice of an aqueous solution of sodium chloride for use as a cathode was justified. The concentration range of an aqueous solution of sodium chloride was established to obtain a homogeneous bulk plasma. A plasma generator has been developed that allows the formation of a powerful plasma flow from the substance of a water-solution cathode. The possibility of supplying gaseous raw materials to an extended discharge gap in a plasma generator has been established. A technical system for the gasification of carbon-containing waste in two stages has been created. In the first stage, the waste was subjected to thermal degradation using an arc plasma, and in the second stage, the volatile components were converted to synthesis gas in a gas-discharge plasma with a water-solution cathode.

The effect of gas injection on energy characteristics of high-current gas discharge with liquid electrolyte cathode

A gas discharge with flowing liquid electrolyte cathode was studied experimentally in high-current combustion conditions under conditions of gas injection into the discharge chamber. The interelectrode distance was 20 cm. Aqueous solutions of sodium chloride with specific electrical conductivity of 10–12 mS/cm were used as electrolyte. The discharge current varied within 14-20 A. The studies were carried out with air blowing at a mass flow rate of up to 2.2 g/s. It is shown that air blowing leads to an increase in the discharge current and decrease heat losses through electrodes.

The features of high-current gas discharge in a narrow gap between the liquid electrolyte and solid electrode

Gas-dynamic phenomena on the boundary "plasma - liquid electrolyte" currents in the range (10 - 21) A were studied. The regularities of the influence of deformation of the surface of the electrolyte on the characteristics of the gas discharge were revealed.

Ionization front in a high-current gas discharge

Spectroscopic measurements of ion/neutral density ratio profiles are made inside the high-current, low-pressure discharge of a coaxial magnetoplasmadynamic thruster and show the existence of a thin ionization front, upstream in the discharge, that effectively ionizes the incoming gas to ionization levels above 50%. The measurements allow an estimate of the width of this ionization front to be on the order of a few millimeters. Due to the known existence of microturbulence in the plasma, which can produce suprathermal electrons, an explanation of the measurements based on the existence of a suprathermal tail in the electron energy distribution function is sought. A theoretical model for the width of the ionization front is combined with a multilevel excitation model for argon and shows that a Maxwellian electron distribution function cannot account for the small length scale of the ionization front, and that the latter is more consistent with an electron distribution function having a suprathermal population, the magnitude of which is estimated by comparing the model to the experiments.

The Influence of an External Permanent Magnetic Field on the Dynamics of Plasma Channels in a Radial Pseudospark Switch

High-current gas discharges can reach current densities of 10/sup 8/ A/cm/sup 2/ in order of magnitude and, therefore, damage the electrodes of nearly all types of low-pressure gas discharge switches. In pseudospark switches with radial geometry, the total current is divided by the number of radial channels and so the current per channel is strongly reduced. However, because of electromagnetic forces the plasma channels attract themselves and pinch together already in the first maximum of the switching current. Therefore, the main advantage of the radial pseudospark switch, the division of the total current, is lost. In this paper, a basic idea of how this movement of the plasma channels can be suppressed, will be introduced. Strong permanent magnets of different types (polarization B/sub x/ of type A: 0.48 T; type B: 1.31 T; and type C: 1.88 T) are attached to the pseudospark switch near the bores of the hollow cathode. The most effective way to apply the magnets was to put them face to face with the bores of the hollow cathode with the center line of the bores and the cylindric magnets coinciding. In this case, the magnetic field looks like a magnetic bottle viewed along the charge carriers path. The magnetic fields capture the plasma channels for a short time and so the pinch effect is delayed until the first maximum of current is over. The investigated pseudospark switch was a radial switch with three channels. The charging voltage was 10 kV and the discharge capacity was 2.2 /spl mu/F, resulting in a total discharge current of 40 kA, respectively, 13.3 kA per channel. In the switch under consideration, the pinching is fulfilled after 800 ns when no magnets are applied. The smallest possible distance between the front of the magnet and the end of the discharge channel was 2 mm. The strength of the magnetic field in this distance with magnets of type A, B, and C was 390, 1065, and 1525 mT, respectively, and the pinching was delayed for 400, 2000, and 1600 ns, accordingly.

Ion beam formation in the field of double layer stabilized by spatial reversal of magnetic field

Abstract The ion beam generation and dynamics of processes in a pulsed straight high-current gas discharge at Iow pressures have been studied. The spatial reversal of a longitudinal con-fining magnetic field is used to stabilize a potential jump. The potential difference of 3–10 kV is applied to the discharge gap filled with a preliminary created plasma. Initially, the precathode potential jump is formed and, thereafter, the auasi-steady double layer arises in the region of magnetic field reversal. Potential difference is concentrated in the double layer, where formation of ion and electron beams occur. A current value of the ion beam formed in the double layer is determined by Bohm's current of the plasma in the anode part of discharge gap (J < 0.6 A/cm2). The ion beam energy is determined by a value of the potential jump (3–10kV) in the double layer. When the plasma with the density higher than the critical one is formed in the system, the magnetic field reversal is self-consistently suppressed; the dou...

Formation of a high-current discharge plasma in metal vapor

A method of converting the energy of a capacitive store into the energy of a high-current gas discharge in aluminum vapor is investigated. The spatial and temporal characteristics of the gas-discharge plasma are studied. The electron temperature, density of charged particles, and conductivity of the plasma are determined.

High current plasma electron emitter

A high current plasma electron emitter based on a miniature plasma source has been developed. The emitting plasma is created by a pulsed high current gas discharge. The electron emission current is 1 kA at 300 V with a pulse duration of 10 ms. The prototype injector described in this paper will be used for a 20 kA electrostatic current injection experiment in the Madison symmetric torus reversed-field pinch. The source will be replicated in order to attain this total current requirement. The source has a simple design and has proven to be very reliable in operation. A high emission current, small size (3.7 cm in diameter) and low impurity generation make the source suitable for a variety of fusion and technological applications.

Formation of a high-current pulsed gas discharge as a source of highly concentrated energy flux to treat metal surfaces

The properties of a novel, pulsed, high-current gas discharge with minimized energy losses are investigated. The discharge provides a highly concentrated energy flux that can be used to treat metal surfaces and to form thin surface layers with desirable properties. A theoretical treatment of the formation of the discharge is presented, and the limitations on its voltage and interelectrode separation length are considered. Experiments are carried out to test the theoretical predictions of the discharge parameters. The experimental results show that more than 80% of the energy input to the discharge from the power supply is delivered to the metal surface. >

Collective interactions and plasma heating in a high current gas discharge

The results are presented of an experimental investigation of processes involved in the development of kinetic instabilities and the heating of a dense plasma in a strong electric field. It is shown that in a high current gas discharge effective heating of both the electron and ion components of the plasma occurs, associated with an anomalous plasma resistivity and intense microwave emission from the plasma at frequencies considerably below the plasma frequency due to the development of high frequency instabilities. The results are discussed and an explanation offered for the mechanism responsible for the development of the instabilities.

MEASUREMENT OF PLASMA DENSITY USING A GAS LASER AS AN INFRARED INTERFEROMETER

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The vacuum switch. Part 1: Properties of the vacuum arc

In any study of switching devices, an understanding of the current conduction processes in the steady or quasi-steady state must precede the investigation of the transient phenomena during the change from the conducting to the insulating state.The paper describes the results of an investigation into the nature of the arcs which are formed when the contacts of a vacuum switch separate. In many respects the vacuum arc is the simplest of all the high-current gas discharges, since there exists no ambient atmosphere to complicate the arcing processes, but this simplicity is only relative, and many assumptions have had to be made to enable a quantitative picture to be built up.The vacuum arc appears to have two very different states; in one, which seems to be the normal condition at currents below about 104A with copper electrodes, the arc is totally unlike high-pressure arcs, and burns as a set of completely separate arcs electrically in parallel. In the other states the arc much more nearly resembles high-pressure arcs.Most of the work described deals with the vacuum arc in the first state, and the density of neutral atoms, ions and electrons in the discharge is calculated as a function of current and position. The influence of the properties of the electrode materials on the arcing voltage and the stability of the arc is described, and the energy balance of the arc is computed.The data from the paper are used in a companion paper to investigate theoretically arc-extinction processes.

Transverse Compression Waves in a Stabilized Discharge

An electric discharge which is compressed by its own magnetic field, and ``stabilized'' by means of an axial magnetic field, can have transverse wave motions which cause its periodic compression and expansion. This kind of motion can cause the heating of the ions in the discharge. The simplest of these wave modes are described and an estimate is given of the power available to the waves as a result of the interaction of the electrons in the discharge with an axial electric field. This interaction can cause the attenuation or spontaneous growth of the waves, depending upon the circumstances. It is likely that in high current gas discharge experiments there are examples of growing and decaying waves of this type.

Investigation of pulsed high current gas discharges by high speed photography

Investigation of pulsed high current gas discharges by high speed photography

Electron temperature and degree of ionization in the initial stage of a pulsed high current gas discharge

Electron temperature and degree of ionization in the initial stage of a pulsed high current gas discharge

Investigation of pulsed high current gas discharges by high speed photography

High speed (106 frames/sec) photographic data on pulsed high energy gas discharges in deuterium and some of the inert gases have been combined with oscillograms of current and voltage to give a qualitative description of the basic processes occurring in the initial stages of a high current discharge. The experimental results confirm the basic conclusions of the inertial theory of plasma constriction worked out by Leontovich and Osovets.

Studies of high current gas discharges at high rates of build-up

Phenomena associated with high current gas discharges in straight tubes are reported. Condenser banks up to 150 mu F and voltages in the range 10 to 30 kv were used in circuits specially devised to give the maximum rate of rise of current. The condensers, which are connected in parallel, are each provided with spark gaps, all of which may be discharged within approximates 10/sup -6/ sec by means of a special triggering circuit. This parallel connection of condensers and spark gaps results in very low inductance, and rates of rise of current in excess of 10/sup 12/ amp/sec. Neutron emission from discharges in deuterium were observed for currents in the range 10/sup 5/ to 10/sup 6/ amperes. Data showing the dependence of neutron production on the circuit inductance, voltage, current, and gas pressure are presented. The quenching effect of impuritiess was investigated, and it was found that neutrons are still observed when as much as 5% of nitrogen is added to the deuterium. In this respect, the results appear to differ from those of other obsevers who have studied similar discharges. The effect of axial magnetic fields on the discharge characteristics is reported. (auth)

Multipole Radiation from High-Current Gas Discharges

RESEARCH in the field of high-current gas discharges is now being pursued vigorously1. In these discharges, where the gas is highly ionized, higher spectra can be predominantly excited (for example, O III, A II) and the pinch effect reduces the loss of ions to the walls. It is thus interesting to consider the possibility of detecting in the laboratory those forbidden lines which are of astrophysical importance.

On the mechanism of current constriction in high-current gas discharges

A theory is given of the mechanism of the current constriction caused by electrodynamic forces.