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Title: Modeling of Radiative Properties of the Wire Array Z-Pinches

Abstract

Recent experiments show that the wire-array z-pinch plasmas are strongly inhomogeneous at small scales. The inhomogeneities are not shot-to-shot reproducible while the arrays provide extremely reproducible x-ray pulses and generate mega-joules of radiation at implosion. This is possible if small-scale structures are averaged in the implosion dynamics and if the energy balance and radiation production are mainly determined by the macroscopic, space-averaged plasma properties. We suggest that the basic physics of radiating wire array implosions could be modeled within a quasi-1D large-scale description. We show that such a quasi-1D hydro model reproduces basic radiative properties of the wire-array z-pinches if the Spitzer resistivity is enhanced by a factor, proportional to {beta}2, where {beta} {omega}e{tau}e is the Hall parameter. It becomes possible to explain the radiation pulse shapes and high experimental efficiency of magnetic energy conversion into radiation in the most powerful laboratory x-ray sources. Our results also reproduce some recently discovered properties of these x-ray sources, such as trailing mass during the implosion and radiation beginning before arrival of the entire imploding mass onto the axis.

Authors:
 [1];  [2];  [3]
  1. Laboratoire de Physique et Technologie des Plasmas, Ecole Polytechnique, 91128 Palaiseau (France)
  2. Icarus Research, Inc., P.O. Box 30780, Bethesda, MD 20824-0780 (United States)
  3. Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375 (United States)
Publication Date:
OSTI Identifier:
20729284
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: 10.1063/1.2159385; (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; COMPUTERIZED SIMULATION; EFFICIENCY; ENERGY CONVERSION; EXPLODING WIRES; IMPLOSIONS; LONGITUDINAL PINCH; MASS; PLASMA; PLASMA SIMULATION; PULSE SHAPERS; PULSES; X RADIATION; X-RAY SOURCES

Citation Formats

Chuvatin, A.S., Rudakov, L.I., and Velikovich, A.L. Modeling of Radiative Properties of the Wire Array Z-Pinches. United States: N. p., 2006. Web. doi:10.1063/1.2159385.
Chuvatin, A.S., Rudakov, L.I., & Velikovich, A.L. Modeling of Radiative Properties of the Wire Array Z-Pinches. United States. doi:10.1063/1.2159385.
Chuvatin, A.S., Rudakov, L.I., and Velikovich, A.L. Thu . "Modeling of Radiative Properties of the Wire Array Z-Pinches". United States. doi:10.1063/1.2159385.
@article{osti_20729284,
title = {Modeling of Radiative Properties of the Wire Array Z-Pinches},
author = {Chuvatin, A.S. and Rudakov, L.I. and Velikovich, A.L.},
abstractNote = {Recent experiments show that the wire-array z-pinch plasmas are strongly inhomogeneous at small scales. The inhomogeneities are not shot-to-shot reproducible while the arrays provide extremely reproducible x-ray pulses and generate mega-joules of radiation at implosion. This is possible if small-scale structures are averaged in the implosion dynamics and if the energy balance and radiation production are mainly determined by the macroscopic, space-averaged plasma properties. We suggest that the basic physics of radiating wire array implosions could be modeled within a quasi-1D large-scale description. We show that such a quasi-1D hydro model reproduces basic radiative properties of the wire-array z-pinches if the Spitzer resistivity is enhanced by a factor, proportional to {beta}2, where {beta} {omega}e{tau}e is the Hall parameter. It becomes possible to explain the radiation pulse shapes and high experimental efficiency of magnetic energy conversion into radiation in the most powerful laboratory x-ray sources. Our results also reproduce some recently discovered properties of these x-ray sources, such as trailing mass during the implosion and radiation beginning before arrival of the entire imploding mass onto the axis.},
doi = {10.1063/1.2159385},
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}
}
  • No abstract prepared.
  • Magneto-hydrodynamic simulations provide a powerful tool for improving our understanding of the complex physical processes underlying the behavior of wire array Z-pinches. We show how, by using large scale parallel 3D simulations of the array as a whole, it is possible to encompass all of the important features of the wire ablation, implosion and stagnation phases and to observe how these phenomena control the X-ray pulse that is achieved. Comparison of code results with experimental data from the 'Z' and MAGPIE pulsed power generators is shown to provide a detailed benchmark test for the models. The simulation results are alsomore » used to highlight key areas for future research.« less
  • X-pinch radiography was used to analyze the interaction between streams of coronal plasma and on-axis foam targets in wire array z-pinch experiments on the MAGPIE generator (1 MA,240 ns). The implosion of the x-pinch, used in place of a current return conductor to the load, provided a short (<2 s) small ({approx}5 {mu}m) intense burst of soft x-rays, ideal for point projection backlighting. Timimg of the x-pinch was adjusted via the mass of its wires, allowing us to study the evolution of the foam during the experiment. Choice of the x-pinch materials, filters, and recording film determined the probing radiation,more » and hence the plasma/foam densities were resolved. Quantitative results will be discussed.« less
  • We are investigating several techniques to obtain time-dependent magnetic field measurements in wire-array Z-pinches and X-pinches. One general approach is to use 'remote sensing' methods whereby a very small sensor material is placed in the plasma and then is investigated to extract useful information. Faraday rotation of polarized laser light traversing a small area through thin film waveguides coupled to a fine optical fiber is a possibility. While these films may not survive for long in a dense Z-pinch, they may provide useful information for a significant fraction of the current pulse. We also discuss results of experiments conducted usingmore » magnetic CoPt thin films to obtain the maximum magnetic field seen by the film near the end of the load current pulse.« less
  • Some issues concerning high-current electron beam transport from the X pinch cross point to the diagnostic system and measurements of the beam current by Faraday cups are discussed. Results of computer simulation of electron beam propagation from the pinch to the Faraday cup give limits for the measured current for beams having different energy spreads. The beam is partially neutralized as it propagates from the X pinch to a diagnostic system, but within a Faraday cup diagnostic, space charge effects can be very important. Experimental results show evidence of such effects.