Vacuum Arc Behavior in a Transverse Magnetic Field

Experimental measurements in a vacuum interrupter have shown that the application of a transverse magnetic field results in substantial increases in arc voltage. Photographic studies of the arc column indicate that strong magnetic fields reduce the effective anode area and may lead to severe arc constriction.     

The High Current Metal Vapor Arc Column between Separating Electrodes

We observed metal vapor arcs between separating electrodes in a demountable vacuum chamber using high speed photography. The peak values of the ac arc current half-wave ranged from 5 kA to 67 kA. Determination of the arc appearance as functions of arc current and electrode gap revealed that the arc can assume various types of columnar forms when the current at the instant of electrode separation exceeds 7 kA. The duration of the columnar arcing forms is influenced by axial magnetic fields differently for different field strengths. The graphical representation of the results allows prediction of the most probable arc appearance for a given set of operating parameters. A qualitative explanation of the various arc appearances on the basis of balances between magnetic and kinetic pressures is provided.     

The Current Distribution and the Magnetic Pressure Profile in a Vacuum Arc Subject to an Axial Magnetic Field

The steady-state electric-current distribution and the magnetic pressure in a uniform conducting medium, flowing in a cylindrical configuration between two circular electrodes, was determined by solving the magnetic field transport equation with a superimposed axial magnetic field. This medium models the interelectrode plasma of the diffuse mode metal vapor vacuum arc. The results show the following. a) The electric current and the flux of the poloidal magnetic field are constricted at the anode side of the flowing plasma. Most of the constriction takes place within a boundary layer, with a characteristic length of 1/Rme, where Rme is the magnetic-Reynolds number for axial electron flow. b) The electric-current constriction inversely depends on K?, where K? is the azimuthal surface current density which produces the axial magnetic field. c) The magnetic-pressure profile shows a radial pinch force in most of the interelectrode region, but in the anode boundary layer it is axially directed, thus retarding the plasma flow. d) The peak of the magnetic pressure is at the anode, and its amplitude directly depends on K?. As K? increases, the peak location moves toward the anode center.     

Behavior of Sustained High-Current Arcs on Molten Alloy Electrodes during Vacuum Consumable Arc Remelting

Vacuum consumable arc remelting is a casting process carried out in a vacuum with the aim of remelting the consumable electrode in such a way that the new ingot has improved chemical and physical homogeneity. The power which causes the melting is supplied by a vacuum arc burning between the electrodes. In order to determine the furnace partitions of electrical power and current, experiments were conducted on molten-faced round electrodes. The quasi-steady melt rate was determined for both horizontally opposed 15-cm-diameter Ni electrodes and for vertically suspended 40-cm-diameter Inconel 718 electrodes. The cathode thermal power is directly proportional to the melt rate which, for the horizontally opposed electrode experiment, agrees to within 10 percent with the Ni breaker switch calorimetry measurements and with predictions from retarded potential analyzer plasma data. However, for the vertically suspended electrode experiments, the measured thermal power at the cathode is 50 percent higher than for nickel. When CO is introduced into the vertical alloy electrode system and electrode gap is increased, the cathode thermal power is reduced by approximately 50 percent. Furthermore, the electrode position measurements and observation of the ingot surface suggest that a concentrated arc is formed under these conditions.     

Influence of a Pulsed Axial Magnetic Field on a High-Current Arc of a Vacuum Circuit Breaker

Russian Physics Journal - The effect of a relatively short external axial magnetic field on the characteristics of a vacuum arc discharge in a vacuum circuit breaker is studied. A pulsed magnetic...     

The Rotation of Ions and Neutrals in a Cylindrical Magnetized Hollow Cathode Argon Arc

In a magnetized hollow cathode arc rotational velocities of ions and neutrals and their temperatures were measured in axial and radial dependence. In comparison with theory experimental results give a detailed analysis of radial transport phenomena.     

Magnetic Field Structure and Induced Electric Current Distribution on a Cylindrical Model： Application to Magnetic Nerve Stimulation

We study the relation between the magnetic field structure and the induced electric-current distribution based on a cylindrical model composed of a uniform electrically conductive medium. When the time-varying magnetic fields are axisymmetrically applied in the axial direction of the model, the electric fields are induced around the central axis in accordance with Faradays law. We examine the eddy-current distributions generated by loop-coils with various geometries carrying an alternating electric current. It is shown that the radial structure of the induced fields can significantly be controlled by the loop coil geometry, which will be suitable for practical use especially in magnetic nerve stimulation on bioelectromagneties, if we appropriately p/ace the exciting coil with optimum geometry.     

Temperature Field Measurements of the Electric Arc Plasma in a Longitudinal Magnetic Field

Two methods are described to determine local parameters of the unsteady asymmetric plasma. The basis of one method is the parametric approach. This method is used to determine plasma parameters in the case when an assumption can be made on the shape of the intensity isolines. The temperature field was calculated according to the intensity distributions in X direction obtained simultaneously from two lines of sight. The second method was applied for measurements in arbitrary plasma configuration. In this case the temperature fields were calculated according to measurements from lines of sight simultaneously, and the obtained data were used in the Radon transformation inversion.     

Electrodes of a Vacuum Chamber under the Action of an Arc in the Explosive Melting Zone

Technical Physics - After repeated exposure to an arc vacuum discharge, Cu (60%)—Cr (40%) alloyed systems show a change in the atomic concentration of copper (from 53.7 to 71.8 at %) and,...     

Current and Voltage Distribution in the Diffuse Vacuum Arc

On the basis of extensive measurements, a model is developed of the diffuse plasma of the high-current vacuum arc. The model shows that the current constriction and the voltage distribution in the diffuse vacuum arc prior to anode-spot formation are caused by the pressure source to which the charged and the neutral particles contribute.     

Investigations of the Current Density in the Cathode Spot of a Vacuum Arc

A short review is given on the problem of the current density in the cathode spot of a vacuum arc, theoretical models and experimental results are discussed. A new measuring method is presented which is directly related to the current carrying area of the spot. It leads to current densities of 10¹² A/m² at clean surfaces (comparable with results obtained from crater measurements) and 10⁹?10¹⁰ A/m² with contaminated surfaces.     

Plasma of Electric Arc Discharge between Melted Electrodes

Plasma of electric arc discharge between melted electrodes was experimentally investigated. Diagnostics of electric arc plasma was carried out. Optical emission and absorption spectroscopy was used to obtain radial profiles of temperature, electron density and neutral atoms concentration. The influence of electrode condition on plasma parameters was evaluated. It was found that the copper vapour in plasma tends to be located at the arc axis.     

Capillary Instability of a Cylindrical Ferrofluid Jet in a Uniform Longitudinal Magnetic Field

Technical Physics - The formulated problem makes it possible to study the influence of magnetic forces on capillary instability of a ferrofluid jet with given physical characteristics in both weak...     

Measurement of the Current Distribution at the Anode in a Low-Current Vacuum Arc

The distribution of the current collected by a multiring anode is measured in a diffuse vacuum arc for several values of the arc current and the electrode separation. It is found that the distribution widens as the electrode separation increases. Comparison with previous measurements suggests an influence of the electrode geometry on the results.     

Magnetic Field Enhancement of the Optogalvanic Signal in a Hollow Cathode Discharge

An optogalvanic signal enhancement was obtained in a magnetic field applied on a hollow cathode discharge-detector. In this magnetic field a mutual correlation was observed between optogalvanic signal behaviour, discharge current change and lower level population of the transition corresponding to the 632,8 nm laser irradiation spectral line.     

Influence of a Non-Stationary Magnetic Field on the Charge Composition and Energy Distribution of Ions of the Cathode Plasma of a Vacuum Arc

Russian Physics Journal - The influence of an external non-stationary axial magnetic field on the charge composition and energy distribution of ions of various charge states in the cathode plasma...     

Global Behavior of Field Line and Particle Diffusion in a Stochastic Magnetic Field

Global behavior of field line diffusion in a stochastic magnetic field is obtained. Stochastic motion of particles undergoing mutural random collisions in the stochastic magnetic field is studied for the whole time range. The field line as wel as the particle diffusion coefficients are calculated to the sixth order of the relative magnitude of the fluctuating magnetic field.     

Anode Melting in a Multicathode-Spot Vacuum Arc

Melting of the anode surface in a multicathode-spot vacuum arc is expected when the incident energy flux is not balanced. The anodic energy influx is proportional to the arc-current collected by the anode and melting of the anode should be observed when peak arc-current exceeds a critical value. In this work, the critical peak arc-current Ipt was measured, and its dependence on anode and cathode materials was determined. The arc was sustained between two parallel cylindrical electrodes, 14 mm in diameter and spaced 4 mm apart. The almost critically damped current pulse lasted for 30 ms with a 6-ms rise time to peak value. Peak currents were in the range of 500-2300 A. In most of the experiments the anode material differed from that of the cathode. In the runs where the cathode-anode materials were Cu-Al or Mo-Cu, respectively, the time dependence of a spectral line intensity radiated by the anode atoms located in the plasma near the anode surface was recorded. We found that Ipt depended on both the anode and cathode materials. Thus for an Al anode and Al and Cu cathodes, Ipt equaled to 1100 and 900 A, respectively. In arcs with a peak current larger or equal to Ipt, a sudden jump of the spectral line intensity was observed. In all experiments, even when strong melting of the anode was observed, the arc-voltage stayed quiescent and in the range 15-35 V, suggesting that no anode spot was formed.