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Title: VUV absorption spectroscopy measurements of the role of fast neutral atoms in a high-power gap breakdown

Abstract

The maximum power achieved in a wide variety of high-power devices, including electron and ion diodes, z pinches, and microwave generators, is presently limited by anode-cathode gap breakdown. A frequently discussed hypothesis for this effect is ionization of fast neutral atoms injected throughout the anode-cathode gap during the power pulse. We describe a newly developed diagnostic tool that provides a direct test of this hypothesis. Time-resolved vacuum-ultraviolet absorption spectroscopy is used to directly probe fast neutral atoms with 1-mm spatial resolution in the 10-mm anode-cathode gap of the SABRE 5 MV, 1 TW applied-B ion diode. Absorption spectra collected during Ar RF glow discharges and with CO{sub 2} gas fills confirm the reliability of the diagnostic technique. Throughout the 50--100 ns ion diode pulses no measurable neutral absorption was seen, setting upper limits of (0.12--1.5)x10{sup 14}cm{sup -3} for ground-state fast neutral atom densities of H, C, N, O, and F. The absence of molecular absorption bands also sets upper limits of (0.16--1.2)x10{sup 15}cm{sup -3} for common simple molecules. These limits are low enough to rule out ionization of fast neutral atoms as a breakdown mechanism. Breakdown due to ionization of molecules is also found to be unlikely. This technique canmore » now be applied to quantify the role of neutral atoms in other high-power devices.« less

Authors:
; ; ; ; ; ;
Publication Date:
Sponsoring Org.:
(US)
OSTI Identifier:
40205413
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review E; Journal Volume: 62; Journal Issue: 6; Other Information: Othernumber: PLEEE8000062000006008485000001; 029012PRE; PBD: Dec 2000
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ABSORPTION; ABSORPTION SPECTRA; ABSORPTION SPECTROSCOPY; ATOMS; BREAKDOWN; DIAGNOSTIC TECHNIQUES; ELECTRONS; GLOW DISCHARGES; HYPOTHESIS; IONIZATION; PROBES; RELIABILITY; SPATIAL RESOLUTION

Citation Formats

Filuk, A. B., Bailey, J. E., Cuneo, M. E., Lake, P. W., Nash, T. J., Noack, D. D., and Maron, Y. VUV absorption spectroscopy measurements of the role of fast neutral atoms in a high-power gap breakdown. United States: N. p., 2000. Web. doi:10.1103/PhysRevE.62.8485.
Filuk, A. B., Bailey, J. E., Cuneo, M. E., Lake, P. W., Nash, T. J., Noack, D. D., & Maron, Y. VUV absorption spectroscopy measurements of the role of fast neutral atoms in a high-power gap breakdown. United States. doi:10.1103/PhysRevE.62.8485.
Filuk, A. B., Bailey, J. E., Cuneo, M. E., Lake, P. W., Nash, T. J., Noack, D. D., and Maron, Y. Fri . "VUV absorption spectroscopy measurements of the role of fast neutral atoms in a high-power gap breakdown". United States. doi:10.1103/PhysRevE.62.8485.
@article{osti_40205413,
title = {VUV absorption spectroscopy measurements of the role of fast neutral atoms in a high-power gap breakdown},
author = {Filuk, A. B. and Bailey, J. E. and Cuneo, M. E. and Lake, P. W. and Nash, T. J. and Noack, D. D. and Maron, Y.},
abstractNote = {The maximum power achieved in a wide variety of high-power devices, including electron and ion diodes, z pinches, and microwave generators, is presently limited by anode-cathode gap breakdown. A frequently discussed hypothesis for this effect is ionization of fast neutral atoms injected throughout the anode-cathode gap during the power pulse. We describe a newly developed diagnostic tool that provides a direct test of this hypothesis. Time-resolved vacuum-ultraviolet absorption spectroscopy is used to directly probe fast neutral atoms with 1-mm spatial resolution in the 10-mm anode-cathode gap of the SABRE 5 MV, 1 TW applied-B ion diode. Absorption spectra collected during Ar RF glow discharges and with CO{sub 2} gas fills confirm the reliability of the diagnostic technique. Throughout the 50--100 ns ion diode pulses no measurable neutral absorption was seen, setting upper limits of (0.12--1.5)x10{sup 14}cm{sup -3} for ground-state fast neutral atom densities of H, C, N, O, and F. The absence of molecular absorption bands also sets upper limits of (0.16--1.2)x10{sup 15}cm{sup -3} for common simple molecules. These limits are low enough to rule out ionization of fast neutral atoms as a breakdown mechanism. Breakdown due to ionization of molecules is also found to be unlikely. This technique can now be applied to quantify the role of neutral atoms in other high-power devices.},
doi = {10.1103/PhysRevE.62.8485},
journal = {Physical Review E},
number = 6,
volume = 62,
place = {United States},
year = {Fri Dec 01 00:00:00 EST 2000},
month = {Fri Dec 01 00:00:00 EST 2000}
}