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Title: 2D radiation-magnetohydrodynamic simulations of SATURN imploding Z-pinches

Abstract

Z-pinch implosions driven by the SATURN device at Sandia National Laboratory are modeled with a 2D radiation magnetohydrodynamic (MHD) code, showing strong growth of magneto-Rayleigh Taylor (MRT) instability. Modeling of the linear and nonlinear development of MRT modes predicts growth of bubble-spike structures that increase the time span of stagnation and the resulting x-ray pulse width. Radiation is important in the pinch dynamics keeping the sheath relatively cool during the run-in and releasing most of the stagnation energy. The calculations give x-ray pulse widths and magnitudes in reasonable agreement with experiments, but predict a radiating region that is too dense and radially localized at stagnation. We also consider peaked initial density profiles with constant imploding sheath velocity that should reduce MRT instability and improve performance. 2D krypton simulations show an output x-ray power > 80 TW for the peaked profile.

Authors:
; ;  [1]
  1. and others
Publication Date:
Research Org.:
Lawrence Livermore National Lab., CA (United States)
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
192472
Report Number(s):
UCRL-JC-122340; CONF-951182-7
ON: DE96005395; TRN: 96:006491
DOE Contract Number:
W-7405-ENG-48
Resource Type:
Conference
Resource Relation:
Conference: 37. annual meeting of the American Physical Society Division of Plasma Physics, Louisville, KY (United States), 6-10 Nov 1995; Other Information: PBD: 6 Nov 1995
Country of Publication:
United States
Language:
English
Subject:
07 ISOTOPE AND RADIATION SOURCE TECHNOLOGY; 66 PHYSICS; LINEAR Z PINCH DEVICES; RAYLEIGH-TAYLOR INSTABILITY; IMPLOSIONS; X-RAY SOURCES; MAGNETOHYDRODYNAMICS; ALUMINIUM; PLASMA SIMULATION

Citation Formats

Hammer, J.H., Eddleman, J.L., and Springer, P.T. 2D radiation-magnetohydrodynamic simulations of SATURN imploding Z-pinches. United States: N. p., 1995. Web.
Hammer, J.H., Eddleman, J.L., & Springer, P.T. 2D radiation-magnetohydrodynamic simulations of SATURN imploding Z-pinches. United States.
Hammer, J.H., Eddleman, J.L., and Springer, P.T. Mon . "2D radiation-magnetohydrodynamic simulations of SATURN imploding Z-pinches". United States. doi:. https://www.osti.gov/servlets/purl/192472.
@article{osti_192472,
title = {2D radiation-magnetohydrodynamic simulations of SATURN imploding Z-pinches},
author = {Hammer, J.H. and Eddleman, J.L. and Springer, P.T.},
abstractNote = {Z-pinch implosions driven by the SATURN device at Sandia National Laboratory are modeled with a 2D radiation magnetohydrodynamic (MHD) code, showing strong growth of magneto-Rayleigh Taylor (MRT) instability. Modeling of the linear and nonlinear development of MRT modes predicts growth of bubble-spike structures that increase the time span of stagnation and the resulting x-ray pulse width. Radiation is important in the pinch dynamics keeping the sheath relatively cool during the run-in and releasing most of the stagnation energy. The calculations give x-ray pulse widths and magnitudes in reasonable agreement with experiments, but predict a radiating region that is too dense and radially localized at stagnation. We also consider peaked initial density profiles with constant imploding sheath velocity that should reduce MRT instability and improve performance. 2D krypton simulations show an output x-ray power > 80 TW for the peaked profile.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Nov 06 00:00:00 EST 1995},
month = {Mon Nov 06 00:00:00 EST 1995}
}

Conference:
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  • Z-pinch implosions driven by the SATURN device [D. D. Bloomquist {ital et} {ital al}., {ital Proceedings} {ital of} {ital the} 6{ital th} {ital Institute} {ital of} {ital Electrical} {ital and} {ital Electronics} {ital Engineers} ({ital IEEE}) {ital Pulsed} {ital Power} {ital Conference}, Arlington, VA, edited by P. J. Turchi and B. H. Bernstein (IEEE, New York, 1987), p. 310] at Sandia National Laboratory are modeled with a two-dimensional radiation magnetohydrodynamic (MHD) code, showing strong growth of the magneto-Rayleigh{endash}Taylor (MRT) instability. Modeling of the linear and nonlinear development of MRT modes predicts growth of bubble-spike structures that increase the time spanmore » of stagnation and the resulting x-ray pulse width. Radiation is important in the pinch dynamics, keeping the sheath relatively cool during the run-in and releasing most of the stagnation energy. The calculations give x-ray pulse widths and magnitudes in reasonable agreement with experiments, but predict a radiating region that is too dense and radially localized at stagnation. We also consider peaked initial density profiles with constant imploding sheath velocity that should reduce MRT instability and improve performance. Krypton simulations show an output x-ray power {approx_gt}80 TW for the peaked profile. {copyright} {ital 1996 American Institute of Physics.}« less
  • Abstract not provided.
  • The magnetic Rayleigh-Taylor (RT) instability has been predicted and observed to cause breakup of the plasma sheath in imploding Z-pinches. In this work we show that for the type of density profile encountered in strongly radiating pinches, instability at very short wavelengths grows to the non-linear stage and seeds progressively longer wavelengths. The result is a self-similar broadening of the sheath as found for mix layers in fluid RT unstable systems.
  • EUV emissions can be used to measure several z-pinch parameters. The authors have measured implosion velocity from Doppler splitting of lines and estimated electron temperature during run-in from the mean ionization state of line emissions. In an argon pinch they measure an electron temperature of 100 eV before stagnation. To date Doppler split lines have measured implosion velocities less than 40 cm/microsecond. They are presently attempting to measure magnetic field or load current from Zeeman splitting and it may be possible to measure electron density from a Stark-broadened line. Opacity and ion thermal broadening may also contribute to line widthmore » information. The spectrometer utilizes a variable line space grating to give a flat focal field. Spectral resolution with a 60 micron detector resolution is up to 3,000 and generally increases with wavelength. This is sufficient to detect several plasma line broadening mechanisms. The spectrometer may detect lines above 100 {angstrom} and below 1,400 {angstrom}. Spectral range across a microchannel plate stripline detector decreases with increasing wavelength setting. The authors may gate two striplines with 1 to 12 nsec gates at any time during the pinch discharge. Each stripline spatially images the pinch diameter perpendicular to the direction of dispersion. Spatial resolution in the pinch diameter is 1 mm. Spatial acquisition along the z axis is also 1 mm. Data are presented from argon, krypton, and aluminum z-pinch discharges on the SATURN accelerator.« less
  • A two dimensional resistive MHD code (MH2D) is applied to the study of the m=0 instability in z-pinches with diffuse profiles. The effects of sheared axial flow and various initial profiles on the non-linear development of Rayleigh-Taylor and MHD instabilities are explored.