NDLI: On the validation of a 3D inflow model for simulating wire array z-pinches, z-pinch energetics, and scaling of radiated power with current

Content Provider	IEEE Xplore Digital Library
Author	Lemke, R.W. Waisman, E.M. Sinars, D.B. Yu, E.P. Haill, T.A. Brunner, T.A. Hanshaw, H.L. Cuneo, M.E. Desjarlais, M.P. Mehlhorn, T.A.
Copyright Year	2008
Description	Author affiliation: Sandia Nat. Labs., Albuquerque, NM (Lemke, R.W.; Waisman, E.M.; Sinars, D.B.; Yu, E.P.; Haill, T.A.; Brunner, T.A.; Hanshaw, H.L.; Cuneo, M.E.; Desjarlais, M.P.; Mehlhorn, T.A.)
Abstract	Summary form only given. Development of a predictive computational model for wire array z-pinches has been inhibited by the 3D nature of the dynamics. We have developed a 3D computational model for simulating cylindrical wire array z-pinches. In lieu of trying to simulate individual wires in the array from the beginning of the initiation phase, which is computationally impractical, we have incorporated a steady state model of wire ablation physics into our 3D, radiation MHD code ALEGRA. Results are presented from a validation study using radiation pulses, currents, and density profiles from a variety of experiments with single wire arrays on the Z accelerator. The wire array is modeled using full length, periodic wedges with angles of 1 and 60 degrees, and 1 degree azimuthal cells. Radiation power pulses produced by arrays with different masses are matched by tuning the ablation rate. Results indicate that the mass ablation rate scales with wire diameter to the -0.49 power, slower than the -0.66 power deduced from experiments. While both wedge models produce power pulses in reasonable agreement with measurements, only the 60 degree wedge with uncorrelated perturbations in azimuth produces both the measured density profile and radiated power. The resulting web-like, azimuthal structure that develops in the z-pinch plasma has a significant influence on the current distribution, density profile and power pulse. Simulations show that shock heating and pdV work account for most of the energy radiated by the z-pinch at stagnation, through peak power. Results indicate that the sub quadratic scaling of peak power (P) with peak current (I) observed in experiments on $Z^{4}$ $(P~I^{1.24plusmn0.18})$ is correlated with significant precursor mass stagnating on axis before the main pinch. For 2.5 and 6.0 mg arrays, the simulated power scales as $P~I^{1.35}$ with a stagnating precursor plasma, and $P~I^{1.8}$ when stagnation of the precursor is precluded by decreasing the implosion time, which is consistent with $P~I^{2}$ based on energy conservation.
Starting Page	1
Ending Page	1
File Size	34478
Page Count	1
File Format	PDF
ISBN	9781424419296
ISSN	07309244
DOI	10.1109/PLASMA.2008.4590764
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2008-06-15
Publisher Place	Germany
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Arrays Wire Solid modeling Computational modeling Plasmas Three dimensional displays Laboratories
Content Type	Text
Resource Type	Article
Subject	Atomic and Molecular Physics, and Optics Condensed Matter Physics Electrical and Electronic Engineering

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