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Title: VUV absorption spectroscopy measurements of the role of fast neutral atoms in 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. The authors describe a newly-developed diagnostic tool that provides the first 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 is seen, setting upper limits of 0.12--1.5 x 10{sup 14} cm{sup {minus}3} for ground state fast neutral atom densities of H, C, N, O, F. The absence of molecular absorption bands also sets upper limits of 0.16--1.2 x 10{sup 15} cm{sup {minus}3} for common simple molecules. These limits are low enough to rule out ionization throughout the gap as a breakdown mechanism. This technique can now be applied to quantifymore » the role of neutral atoms in other high-power devices.« less

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Sandia National Labs., Albuquerque, NM (US); Sandia National Labs., Livermore, CA (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
752820
Report Number(s):
SAND2000-0719J
TRN: US0003247
DOE Contract Number:  
AC04-94AL85000
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review E; Other Information: Submitted to Physical Review E; PBD: 20 Mar 2000
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; INERTIAL FUSION DRIVERS; ION SOURCES; PLASMA DIAGNOSTICS; ABSORPTION SPECTROSCOPY; FAR ULTRAVIOLET RADIATION; NEUTRAL PARTICLES; HYDROGEN; CARBON; NITROGEN; OXYGEN; FLUORINE

Citation Formats

FILUK,A.B., BAILEY,JAMES E., CUNEO,MICHAEL E., LAKE,PATRICK WAYNE, NASH,THOMAS J., NOACK,DONALD D., and MARON,Y. VUV absorption spectroscopy measurements of the role of fast neutral atoms in high-power gap breakdown. United States: N. p., 2000. Web. doi:10.1103/PhysRevE.62.8485.
FILUK,A.B., BAILEY,JAMES E., CUNEO,MICHAEL E., LAKE,PATRICK WAYNE, NASH,THOMAS J., NOACK,DONALD D., & MARON,Y. VUV absorption spectroscopy measurements of the role of fast neutral atoms in high-power gap breakdown. United States. doi:10.1103/PhysRevE.62.8485.
FILUK,A.B., BAILEY,JAMES E., CUNEO,MICHAEL E., LAKE,PATRICK WAYNE, NASH,THOMAS J., NOACK,DONALD D., and MARON,Y. Mon . "VUV absorption spectroscopy measurements of the role of fast neutral atoms in high-power gap breakdown". United States. doi:10.1103/PhysRevE.62.8485. https://www.osti.gov/servlets/purl/752820.
@article{osti_752820,
title = {VUV absorption spectroscopy measurements of the role of fast neutral atoms in high-power gap breakdown},
author = {FILUK,A.B. and BAILEY,JAMES E. and CUNEO,MICHAEL E. and LAKE,PATRICK WAYNE and NASH,THOMAS J. and NOACK,DONALD 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. The authors describe a newly-developed diagnostic tool that provides the first 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 is seen, setting upper limits of 0.12--1.5 x 10{sup 14} cm{sup {minus}3} for ground state fast neutral atom densities of H, C, N, O, F. The absence of molecular absorption bands also sets upper limits of 0.16--1.2 x 10{sup 15} cm{sup {minus}3} for common simple molecules. These limits are low enough to rule out ionization throughout the gap as a breakdown mechanism. 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 = ,
volume = ,
place = {United States},
year = {Mon Mar 20 00:00:00 EST 2000},
month = {Mon Mar 20 00:00:00 EST 2000}
}