Showing papers on "Plasma channel published in 1990"
TL;DR: In this article, a direct current are plasma generator is described, which uses a concentric electrode configuration and a magnetic field parallel to the electrode axis to obtain rotation of the are current channel at a frequency in the 1-3 kHz range.
Abstract: A direct-current are plasma generator is described which uses a concentric electrode configuration and a magnetic field parallel to the electrode axis to obtain rotation of the are current channel at a frequency in the 1-3 kHz range. The anode is a hollow graphite cylinder, and the cathode is a thoriated tungsten wire. A magnetic field of several hundred gauss is obtained from one or more ring-shaped permanent ceramic magnets. For a 5-mm anode diameter, the plasma is diffuse, and the current channel has the form of a thin radial sheet which undergoes relatively small periodic perturbations at the rotational frequency. Design features, performance data, and plasma structure are considered.
23 citations
TL;DR: The growth rate of the ion-hose instability has been measured for a 2.5 MeV, 1 kA, 1 μsec electron beam following plasma channels of O2, N2, and H2 (in the ion focused regime).
Abstract: The growth rate of the ion‐hose instability has been measured for a 2.5 MeV, 1 kA, 1 μsec electron beam following plasma channels of O2, N2, and H2 (in the ion‐focused regime). The amplitude of transverse oscillations of a given beam segment was seen to grow, saturate, and damp as the segment traveled. The offset amplitude at saturation (dm) was seen to be an exponential function of the beam pulse duration (t): dm=dm,0 exp(2πGLt/tc), where tc is the time required for one channel oscillation and GL is the growth rate (for beam oscillations less than the channel radius). With beam radius equal to channel radius (rb=rc), and channel density equal to half the beam density, GL=0.75±0.15. Here GL was seen to scale with the square root of channel ion mass when data from channels of O2, N2, and H2 were compared. Also, GL was seen to increase as rb was increased (with the initial beam emittance kept the same). A fivefold decrease in growth rate was observed for t>tc and dm>rc. The decrease in growth rate may be du...
15 citations
Patent•
16 Oct 1990TL;DR: In this article, an arrangement for comminution of concrements of various kinds in the body of living being, uses an underwater or submerged arc gap with spark discharge, and an electrical energizing circuitry for that arc gap, a plurality of electrode assemblies from which one is selected to be used in the equipment is connected to the energizing circuit; the electrode assemblies are basically similarly configured and each has an ohmic resistor which is connected directly in series with one of the electrodes.
Abstract: An arrangement for the comminution of concrements of various kinds in the body of living being, uses an underwater or submerged arc gap with spark discharge, and an electrical energizing circuitry for that arc gap, a plurality of electrode assemblies from which one is selected to be used in the equipment is connected to the energizing circuit; the electrode assemblies are basically similarly configured and each has an ohmic resistor which is connected directly in series with one of the electrodes, the resistance value for the resistors in the electrode assemblies of the plurality are different, and in each instance much lower than the resistance of the unignited gap, but of comparable magnitude with the resistance of a fully developed plasma channel in the gap following ignition by the energizing circuit.
4 citations
TL;DR: In this article, experimental results of measurements of the conductivity of a plasma channel produced by a high-current relativistic electron beam (REB) in a gas mixture N 2 :O 2 of various pressures were presented.
4 citations
TL;DR: In this paper, the authors showed that the post-disruption plasma is about a resistive tearing time, which is consistent with measured plasma current decay times of 1-3 ms, characteristic of resistive 10 eV plasma.
2 citations
TL;DR: In this paper, the linearized tracking force on an electron beam propagating slightly off axis in an Ohmic plasma channel is calculated using the frozen field approximation of the Maxwell field equations.
Abstract: The linearized tracking force on an electron beam propagating slightly off axis in an Ohmic plasma channel is calculated. Electron inertial effects are included in Ohm’s law. The channel of conductivity (σ), density (ne), and radius (a) is surrounded by a region of ambient plasma with conductivity (σ0), density (ne0), and radius (b). Enclosing the system is a highly conducting metallic tank. The electromagnetic fields are calculated using the frozen‐field approximation of the Maxwell field equations. The fields are expanded into monopole and dipole moments linearized in the small parameter (d/a), where (d) is the beam displacement. The electron beam is assumed to be a rigid cylinder of charge propagating at the speed of light through the channel and is not allowed to respond dynamically to the force.
2 citations
02 Jul 1990
TL;DR: In this paper, at microsecond conduction times and both 200 and 800 kA current levels, the authors showed that a current channel is seen to propagate toward the load, and this channel is associated with an increased ion current and cathode and switch plasma luminosity.
Abstract: Plasma erosion opening switch conduction phase studies. at microsecond conduction times and both 200 and 800 kA current levels, are reported here. Similar data were obtained from both experiments. A current channel is seen to propagate toward the load, and this channel is associated with an increased ion current and cathode and switch plasma luminosity. There is evidence of local opening during the conduction phase. which may be related to hydrodynamic effects.
1 citations
02 Jul 1990
TL;DR: In this paper, a low impedance phase was observed whose duration could be controlled by the gas pressure and the initial plasma current, at the end of which the diode voltage and impedance rise abruptly with observed switching times less than 10 ns.
Abstract: Plasma filled diode experiments have been performed at .1 to .5 TW by producing a hollow, Penning like, discharge in low pressure gas inside the A-K gap of an electron beam diode. A low impedance phase was observed whose duration could be controlled by the gas pressure and the initial plasma current. At the end of this low impedance phase, the diode voltage and impedance rise abruptly with observed switching times less than 10 ns.
1 citations
TL;DR: In this article, a theoretical study of the formation and current neutralization of a high current electron beam into nitrogen under high pressure (p ≥ 70 torr) was performed, where the complex ion formation and recombination mechanism was considered together with its effect on the parameters of the plasma formed and the dynamics of beam current neutralisation.
Abstract: A theoretical study is performed of plasma channel formation and current neutralization upon injection of a high current electron beam into nitrogen under high pressure (p ≥ 70 torr). The complex ion formation and recombination mechanism is considered together with its effect on the parameters of the plasma formed and the dynamics of beam current neutralization. Analytical expressions are obtained for the densities of simple and complex ions in the limiting cases and numerical calculations are carried out by computer for a more general case. It is shown that in nitrogen at a pressure of 70 torr when complex ions are considered the plasma channel conductivity decreases by approximately 35–40%.