56th Annual Meeting of the APS Division of Plasma Physics
Volume 59, Number 15
Monday–Friday, October 27–31, 2014;
New Orleans, Louisiana
Session TI2: ICF and Z-pinch Physics
9:30 AM–12:30 PM,
Thursday, October 30, 2014
Room: Bissonet
Chair: Patrick McKenty, University of Rochester
Abstract ID: BAPS.2014.DPP.TI2.6
Abstract: TI2.00006 : Computational modeling of Krypton Gas Puffs on Z*
12:00 PM–12:30 PM
Preview Abstract
Abstract
Author:
Christopher Jennings
(Sandia National Laboratories)
Large diameter multi-shell gas puffs rapidly imploded by high current
($\sim$ 20MA, $\sim$ 100ns) on the Z generator of Sandia
National Laboratories are able to produce high-intensity K-shell radiation.
Experiments are currently underway to produce Krypton K-shell emission at
$\sim$ 13keV, from double annular shell gas puffs imploded from a
12cm diameter onto a central gas jet. Efficiently radiating at these high
photon energies represents a significant challenge which necessitates the
careful design and optimization of the gas distribution. To facilitate this
we hydro-dynamically model the gas flow out of the nozzle, before imploding
that mass distribution using a 3-dimensional resistive, radiative MHD code
(GORGON). We present details of how modeled gas profiles are validated
against 2-dimensional interferometric measurements of the initial gas
distribution, and MHD calculations are validated against power, yield,
spectral and imaging diagnostics of the experiments. This approach has
enabled us to iterate between modeling the implosion and gas flow from the
nozzle to optimize radiative output from this combined system. Guided by our
implosion calculations we have designed and implemented gas profiles that
help mitigate disruption from Magneto-Rayleigh--Taylor implosion
instabilities, while preserving sufficient kinetic energy to thermalize to
the high temperatures required for K-shell emission. Predicted increases in
yield from introducing a relief feature into the inner gas nozzle to create
a radially increasing density distribution were recovered in experiment.
K-shell yield is predicted to further increase by the introduction of an
on-axis gas jet, although the mass of this jet must be carefully selected
with respect to the delivered current to avoid reducing the yield. For Kr
gas puffs the predicted K-shell yield increase from addition of a light
central jet was realized in the experiments, considerably increasing the
yield over previous results. Further confidence in our ability to model
different gas profiles was added by comparisons with smaller diameter Ar gas
puffs, where simulations reproduce the effect of a central jet for different
gas profiles.
*Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's NNSA under contract DE-AC04-94AL85000.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2014.DPP.TI2.6