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Title: Properties of Plasma Jets Emitted in Pulsed Capillary Discharges

Abstract

The basic properties of plasma jets emitted by pulsed capillary discharges (PCD) are investigated. The PCD operates with a {approx}2 kA, 10 ns current pulse, in argon in the 0.5-100 Torr pressure range. The electron density in the high pressure range, 20-100 Torr is measured with a time resolved Michelson interferometer and in the low pressure range, below 1 Torr, with a fast Langmuir probe. Characteristic values for the electron density are of order of 1017 cm{sup -3}, for high pressure operation, and 1014 cm{sup -3}, for the lower pressure range. In this limit, the characteristic electron temperature of the plasma jets is found to be in the 10 to 20 eV range.

Authors:
; ; ; ; ; ;  [1]
  1. Departamento de Fisica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile)
Publication Date:
OSTI Identifier:
20729260
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 808; Journal Issue: 1; Conference: 6. international conference on dense Z-pinches, Oxford (United Kingdom), 25-28 Jul 2005; Other Information: DOI: 10.1063/1.2159363; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ARGON; CAPILLARIES; ELECTRIC CURRENTS; ELECTRIC DISCHARGES; ELECTRON DENSITY; ELECTRON TEMPERATURE; EMISSION; EV RANGE; LANGMUIR PROBE; MICHELSON INTERFEROMETER; PLASMA JETS; PLASMA PRODUCTION; PRESSURE RANGE MEGA PA 10-100; PULSES; TIME RESOLUTION

Citation Formats

Avaria, G., Bhuyan, H., Caballero, L.S., Chuaqui, H., Favre, M., Mitchell, I., and Wyndham, E. Properties of Plasma Jets Emitted in Pulsed Capillary Discharges. United States: N. p., 2006. Web. doi:10.1063/1.2159363.
Avaria, G., Bhuyan, H., Caballero, L.S., Chuaqui, H., Favre, M., Mitchell, I., & Wyndham, E. Properties of Plasma Jets Emitted in Pulsed Capillary Discharges. United States. doi:10.1063/1.2159363.
Avaria, G., Bhuyan, H., Caballero, L.S., Chuaqui, H., Favre, M., Mitchell, I., and Wyndham, E. Thu . "Properties of Plasma Jets Emitted in Pulsed Capillary Discharges". United States. doi:10.1063/1.2159363.
@article{osti_20729260,
title = {Properties of Plasma Jets Emitted in Pulsed Capillary Discharges},
author = {Avaria, G. and Bhuyan, H. and Caballero, L.S. and Chuaqui, H. and Favre, M. and Mitchell, I. and Wyndham, E.},
abstractNote = {The basic properties of plasma jets emitted by pulsed capillary discharges (PCD) are investigated. The PCD operates with a {approx}2 kA, 10 ns current pulse, in argon in the 0.5-100 Torr pressure range. The electron density in the high pressure range, 20-100 Torr is measured with a time resolved Michelson interferometer and in the low pressure range, below 1 Torr, with a fast Langmuir probe. Characteristic values for the electron density are of order of 1017 cm{sup -3}, for high pressure operation, and 1014 cm{sup -3}, for the lower pressure range. In this limit, the characteristic electron temperature of the plasma jets is found to be in the 10 to 20 eV range.},
doi = {10.1063/1.2159363},
journal = {AIP Conference Proceedings},
number = 1,
volume = 808,
place = {United States},
year = {Thu Jan 05 00:00:00 EST 2006},
month = {Thu Jan 05 00:00:00 EST 2006}
}
  • The characteristic geometry of a pulsed capillary discharge (PCD), a narrow open end tube with a large aspect ratio, establishes natural conditions for the generation of plasma jets, that propagate in the neutral background gas surrounding the capillary. We have investigated the plasma jet emission in a PCD, with electron beam assisted on-axis initiation. A local storage capacitor, coaxial with the capillary assembly, is pulse charged up to a maximum of -11 kV, which results in an initial {approx} 10 ns, {approx} 2 kA current pulse. The discharge is operated in Argon and Nitrogen, in a continuous pulsing mode, atmore » frequencies between 5 to 20 Hz, and in a pressure range between 300 to 1100 Torr. A fast Langmuir probe, placed at the anode side, close to the capillary exit, is used to measure the characteristic electron temperature (Te) and electron density (Ne) of the plasma jets. Results obtained in Nitrogen at 10 Hz indicate that Te is in the 10 to 60 eV range with Ne of the order of 1014 (cm-3). Significant changes in the probe floating potential are observed for a fixed operating pressure when the pulsing frequency is varied, which can be ascribed to the presence of metastables in the gas fed into the capillary, which result from the interaction of the plasma jet with the plenum gas, at the cathode side. The presence of metastables reduces the energy cost involved in the capillary plasma production, which results in a pulsing frequency dependence of the plasma parameters.« less
  • The properties of a plasma jet generated in low-pressure pulsed capillary discharge have been measured. The discharge operates in a 5 cm long and 1.6-mm-inner diameter alumina capillary, with argon in a pressure range between 20 and 100 Torr, at 11-kV applied voltage. The temporal and spatial evolutions of the plasma density in the plasma jets are measured close to the capillary end with a Michelson interferometry based on a 10-ns-pulse Nd:yttrium aluminum garnet laser. The maximum on-axis plasma density is of the order of 10{sup 17} cm{sup -3} at the capillary output, with an {approx}6-ns rise time to reachmore » a significative electron density. At lower pressure the plasma density is seen to decay in a time scale of 50 ns and over an axial distance of the order of 0.5 mm, whereas at the higher pressure, 100 Torr, it remains more or less stationary for up to {approx}300 ns. The discharge is characterized by a high efficiency in energy coupling, as the local-stored energy is much less than 1 J per pulse.« less
  • Experimental investigations were conducted on the discharge and generation characteristics of a CO/sub 2/ laser with UV preionization. The voltage stability limits of a volume discharge were found as functions of the pressure and the composition of the gas mixture. Optimization of the laser parameters made it possible to obtain an energy output >20 J/liter at atmosphere pressure in a mixture containing nitrogen and >6 J/liter in a CO/sub 2/:He mixture. Using breakdown at the focal point of the lens, we obtained a pulse of radiation with an energy approx.0.5 J and a full-width at half-maximum approx.50 ns.
  • Qualitative analysis of the emission spectra of pulsed discharges through a capillary in argon, krypton, and xenon at initial pressures of 1.3-40 kPa showed that the line spectrum, which is particularly apparent at 1.3 kPa, does not contain lines of multiply charged ions of the contained gas or the capillary erosion products. The argon spectrum at 40 kPa includes, besides singly ionized silicon lines, also an Ar II 157.2-160.2 series, with excitation potentials up to 26 eV. It was experimentally shown that under certain conditions a sealed xuv-radiation source can be made with pulsed discharges through a capillary in anmore » inert gas. To this end it is necessary to reduce erosion of the capillary by using gas under high pressure.« less
  • Previous investigations show that the electric breakdown process in shielded capillary discharges with a hollow cathode geometry is characterized by the propagation of an anode directed high speed ionization wave (HSIW). To further investigate HSIW assisted capillary discharges with negative polarity, we have performed detailed experiments in argon, at pressures between 0.2 and 1.0 Torr. For these pressures, a characteristic ionization wave speed in the 0.1-3.0 x 107 m/s range is observed. The speed and amplitude of the wave are seen to decrease as the wave propagates along the capillary axis. As a result of these investigations, the role ofmore » the hollow cathode electron beams is clearly identified and the HSIW is established as the dominant mechanism for electric breakdown in low pressure capillary discharges, sharing most of the features previously observed in much larger coaxial discharge devices.« less