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Title: Recent Results for Large Diameter (12 cm) Gas Puff Z-Pinches at Peak Currents of >3 to <6 MA

Abstract

There is strong interest in many laboratories worldwide in utilizing less expensive, longer rise-time (> 200 ns) pulsed power to drive x-ray producing z-pinches. Based on the idea of a magnetically-driven annular implosion, the emission of K-shell photons requires high energy per ion (implosion velocity above 43 cm/{mu}s for argon) to strip the atoms to the helium-like and hydrogen-like states. This high velocity must be combined with high density in the final hot plasma to produce significant x-ray yield. To first order, implosion velocity correlates with the initial diameter of the z-pinch load in proportion to the implosion time. Thus some effort has been made in the last few years to develop larger diameter z-pinch loads suitable for use with the longer rise-time drivers. Advancing from the <4 cm diameter loads (used for 100 ns implosions) of a decade ago, progress with 8 cm loads was reported at the last DZP meeting. Here we review further progress with 12 cm loads as used to date at peak currents of 3.5 MA to almost 6 MA with >200 ns implosion times. The most interesting result is that implosions from 12 cm diameter have not proven hopelessly unstable. High quality pinches withmore » few millimeter K-shell emitting diameters, <5 ns pulse widths, electron temperatures above 1.7 keV and ion densities >4*1019/cm{sup 3} have been achieved. The observed argon K yield has equaled simple scaling estimates that ignore the expected increase in instabilities for large initial diameters. This more stable result probably occurs because we are using radial mass distributions that are 'snowplow' stabilized, i.e., they are not shell-like but rather have smoothly varying mass with the radial density gradient, d{rho}/dr small or negative over much of the gas flow. Data on yield as a function of the radial distribution suggest that a near or on-axis peak in the initial gas density is probably optimal. Work remains to be done to establish the details of the 'best' mass distribution.« less

Authors:
; ;  [1]; ; ; ; ;  [2]; ; ; ;  [3];  [4];  [5]
  1. Alameda Applied Sciences Corp, 626 Whitney St, San Leandro CA, 94577 (United States)
  2. Titan Pulsed Sciences Division, 2700 Merced St., San Leandro, CA 94577 (United States)
  3. Naval Reearch Laboratory, Code 6720, 4555 Overlook Ave SW, Washington DC 20375 (United States)
  4. Naval Reearch Laboratory, Code 6770, 4555 Overlook Ave SW, Washington DC 20375 (United States)
  5. Defense Threat Reduction Agency, Kirtland AFB, Albuquerque, NM 87117 (United States)
Publication Date:
OSTI Identifier:
20729240
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: 10.1063/1.2159344; (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; ELECTRIC CURRENTS; ELECTRON TEMPERATURE; GAS FLOW; HELIUM; HOT PLASMA; HYDROGEN; IMPLOSIONS; ION DENSITY; K SHELL; KEV RANGE; LINEAR Z PINCH DEVICES; LONGITUDINAL PINCH; MASS DISTRIBUTION; PHOTONS; PLASMA DENSITY; PLASMA INSTABILITY; PULSE RISE TIME; X RADIATION

Citation Formats

Coleman, P.L., Krishnan, M., Thompson, J.R., Banister, J.W., Failor, B.H., Levine, J.S., Qi, N., Sze, H.M., Apruzese, J.P., Davis, J., Thornhill, J.W., Velikovich, A.L., Commisso, R.J., and Verma, A. Recent Results for Large Diameter (12 cm) Gas Puff Z-Pinches at Peak Currents of >3 to <6 MA. United States: N. p., 2006. Web. doi:10.1063/1.2159344.
Coleman, P.L., Krishnan, M., Thompson, J.R., Banister, J.W., Failor, B.H., Levine, J.S., Qi, N., Sze, H.M., Apruzese, J.P., Davis, J., Thornhill, J.W., Velikovich, A.L., Commisso, R.J., & Verma, A. Recent Results for Large Diameter (12 cm) Gas Puff Z-Pinches at Peak Currents of >3 to <6 MA. United States. doi:10.1063/1.2159344.
Coleman, P.L., Krishnan, M., Thompson, J.R., Banister, J.W., Failor, B.H., Levine, J.S., Qi, N., Sze, H.M., Apruzese, J.P., Davis, J., Thornhill, J.W., Velikovich, A.L., Commisso, R.J., and Verma, A. Thu . "Recent Results for Large Diameter (12 cm) Gas Puff Z-Pinches at Peak Currents of >3 to <6 MA". United States. doi:10.1063/1.2159344.
@article{osti_20729240,
title = {Recent Results for Large Diameter (12 cm) Gas Puff Z-Pinches at Peak Currents of >3 to <6 MA},
author = {Coleman, P.L. and Krishnan, M. and Thompson, J.R. and Banister, J.W. and Failor, B.H. and Levine, J.S. and Qi, N. and Sze, H.M. and Apruzese, J.P. and Davis, J. and Thornhill, J.W. and Velikovich, A.L. and Commisso, R.J. and Verma, A.},
abstractNote = {There is strong interest in many laboratories worldwide in utilizing less expensive, longer rise-time (> 200 ns) pulsed power to drive x-ray producing z-pinches. Based on the idea of a magnetically-driven annular implosion, the emission of K-shell photons requires high energy per ion (implosion velocity above 43 cm/{mu}s for argon) to strip the atoms to the helium-like and hydrogen-like states. This high velocity must be combined with high density in the final hot plasma to produce significant x-ray yield. To first order, implosion velocity correlates with the initial diameter of the z-pinch load in proportion to the implosion time. Thus some effort has been made in the last few years to develop larger diameter z-pinch loads suitable for use with the longer rise-time drivers. Advancing from the <4 cm diameter loads (used for 100 ns implosions) of a decade ago, progress with 8 cm loads was reported at the last DZP meeting. Here we review further progress with 12 cm loads as used to date at peak currents of 3.5 MA to almost 6 MA with >200 ns implosion times. The most interesting result is that implosions from 12 cm diameter have not proven hopelessly unstable. High quality pinches with few millimeter K-shell emitting diameters, <5 ns pulse widths, electron temperatures above 1.7 keV and ion densities >4*1019/cm{sup 3} have been achieved. The observed argon K yield has equaled simple scaling estimates that ignore the expected increase in instabilities for large initial diameters. This more stable result probably occurs because we are using radial mass distributions that are 'snowplow' stabilized, i.e., they are not shell-like but rather have smoothly varying mass with the radial density gradient, d{rho}/dr small or negative over much of the gas flow. Data on yield as a function of the radial distribution suggest that a near or on-axis peak in the initial gas density is probably optimal. Work remains to be done to establish the details of the 'best' mass distribution.},
doi = {10.1063/1.2159344},
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}
}