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Title: Tomographic interferometry of a filtered high-current vacuum arc plasma

Abstract

Tomography of a plasma enables the distribution of electron density to be visualized. We report on the design of two tomographic interferometer systems used to measure plasma electron density distributions in a high-current pulsed cathodic vacuum arc. The method is shown to be capable of microsecond time resolution. The spatial resolution of the quasioptical interferometer operating at 2 mm wavelength is 20 mm and the spatial resolution of the waveguide-based interferometer operating at 8 mm wavelength is 50 mm. In both cases the resolution achieved depends on the launching and receiving geometries. We developed criteria for assessing the tomogram for artifacts arising from limited sampling. First results of the spatial and temporal history of plasma in a high-current vacuum arc guided by a curved magnetic filter are presented and indicate poloidal field fluctuations reminiscent of magnetohydrodynamic instabilities in pinches. The applicability of the tomographic interferometry method to optimize plasma transport through the filter is also demonstrated.

Authors:
; ; ; ; ; ;  [1];  [2];  [3]
  1. School of Physics (A28), The University of Sydney, NSW 2006 (Australia)
  2. (United States)
  3. (Australia)
Publication Date:
OSTI Identifier:
20982785
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 101; Journal Issue: 7; Other Information: DOI: 10.1063/1.2714677; (c) 2007 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; ELECTRON DENSITY; INTERFEROMETERS; INTERFEROMETRY; MAGNETIC FILTERS; MAGNETOHYDRODYNAMICS; PINCH EFFECT; PLASMA; PLASMA DENSITY; PLASMA DIAGNOSTICS; PLASMA INSTABILITY; SPATIAL RESOLUTION; TIME RESOLUTION; TOMOGRAPHY; WAVEGUIDES; WAVELENGTHS

Citation Formats

Warr, George B., Tarrant, Richard N., Bilek, Marcela M. M., McKenzie, David R., Harris, Jeffrey H., Howard, John, Blackwell, Boyd D., Fusion Energy Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6169, and Plasma Research Laboratory, Research School of Physical Sciences and Engineering, Australian National University, Canberra, ACT 0200. Tomographic interferometry of a filtered high-current vacuum arc plasma. United States: N. p., 2007. Web. doi:10.1063/1.2714677.
Warr, George B., Tarrant, Richard N., Bilek, Marcela M. M., McKenzie, David R., Harris, Jeffrey H., Howard, John, Blackwell, Boyd D., Fusion Energy Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6169, & Plasma Research Laboratory, Research School of Physical Sciences and Engineering, Australian National University, Canberra, ACT 0200. Tomographic interferometry of a filtered high-current vacuum arc plasma. United States. doi:10.1063/1.2714677.
Warr, George B., Tarrant, Richard N., Bilek, Marcela M. M., McKenzie, David R., Harris, Jeffrey H., Howard, John, Blackwell, Boyd D., Fusion Energy Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6169, and Plasma Research Laboratory, Research School of Physical Sciences and Engineering, Australian National University, Canberra, ACT 0200. Sun . "Tomographic interferometry of a filtered high-current vacuum arc plasma". United States. doi:10.1063/1.2714677.
@article{osti_20982785,
title = {Tomographic interferometry of a filtered high-current vacuum arc plasma},
author = {Warr, George B. and Tarrant, Richard N. and Bilek, Marcela M. M. and McKenzie, David R. and Harris, Jeffrey H. and Howard, John and Blackwell, Boyd D. and Fusion Energy Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6169 and Plasma Research Laboratory, Research School of Physical Sciences and Engineering, Australian National University, Canberra, ACT 0200},
abstractNote = {Tomography of a plasma enables the distribution of electron density to be visualized. We report on the design of two tomographic interferometer systems used to measure plasma electron density distributions in a high-current pulsed cathodic vacuum arc. The method is shown to be capable of microsecond time resolution. The spatial resolution of the quasioptical interferometer operating at 2 mm wavelength is 20 mm and the spatial resolution of the waveguide-based interferometer operating at 8 mm wavelength is 50 mm. In both cases the resolution achieved depends on the launching and receiving geometries. We developed criteria for assessing the tomogram for artifacts arising from limited sampling. First results of the spatial and temporal history of plasma in a high-current vacuum arc guided by a curved magnetic filter are presented and indicate poloidal field fluctuations reminiscent of magnetohydrodynamic instabilities in pinches. The applicability of the tomographic interferometry method to optimize plasma transport through the filter is also demonstrated.},
doi = {10.1063/1.2714677},
journal = {Journal of Applied Physics},
number = 7,
volume = 101,
place = {United States},
year = {Sun Apr 01 00:00:00 EDT 2007},
month = {Sun Apr 01 00:00:00 EDT 2007}
}
  • Studies of plasma behavior produced by a filtered high current pulsed cathodic vacuum arc system are reported. Titanium plasma is initiated from the cathode by surface flash over triggering at the centre of the cathode disk. The multiple arc spots move outwards due to their mutual repulsion and the arc current pulse is terminated as the arc spots reach the edge of the cathode disk. The plasma moves into a positively biased quarter-torus magnetic filter and is guided towards the substrate position located 150 mm beyond the filter exit. Electron density and plasma current measurements have been employed to analyzemore » the transport of the plasma associated with different cathode currents, and its dependence on confining magnetic field and bias conditions. For a given cathode current, the optimum plasma transport to the substrate requires the right combination of the strength of the confining magnetic field and the magnetic filter positive bias. The optimum values of these two parameters were found to increase with increasing cathode current. Initially the optimum throughput of plasma increases more strongly than the arc current (roughly 1.5 times the increase in the current); however, at high cathode current regimes (2.4 kA) a significant change of the plasma behavior is seen and transport efficiency is reduced.« less
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