Bulletin of the American Physical Society
50th Annual Meeting of the Division of Plasma Physics
Volume 53, Number 14
Monday–Friday, November 17–21, 2008; Dallas, Texas
Session QI1: Shocks and Shock-Driven Phenomena in High-Energy Density Plasmas |
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Chair: Vladimir Smalyuk, University of Rochester Room: Landmark A |
Wednesday, November 19, 2008 3:00PM - 3:30PM |
QI1.00001: Laboratory blast wave driven instabilities Invited Speaker: This presentation discusses experiments involving the evolution of hydrodynamic instabilities in the laboratory under high-energy-density (HED) conditions. These instabilities are driven by blast waves, which occur following a sudden, finite release of energy, and consist of a shock front followed by a rarefaction wave. When a blast wave crosses an interface with a decrease in density, hydrodynamic instabilities will develop. Instabilities evolving under HED conditions are relevant to astrophysics. These experiments include target materials scaled in density to the He/H layer in SN1987A. About 5 kJ of laser energy from the Omega Laser facility irradiates a 150 $\mu $m plastic layer that is followed by a low-density foam layer. A blast wave structure similar to those in supernovae is created in the plastic layer. The blast wave crosses an interface having a 2D or 3D sinusoidal structure that serves as a seed perturbation for hydrodynamic instabilities. This produces unstable growth dominated by the Rayleigh-Taylor (RT) instability in the nonlinear regime. We have detected the interface structure under these conditions using x-ray backlighting. Recent advances in our diagnostic techniques have greatly improved the resolution of our x-ray radiographic images. Under certain conditions, the improved images show some mass extending beyond the RT spike and penetrating further than previously observed or predicted by current simulations. The observed effect is potentially of great importance as a source of mass transport to places not anticipated by current theory and simulation. I will discuss the amount of mass in these spike extensions, the associated uncertainties, and hypotheses regarding their origin We also plan to show comparisons of experiments using single mode and multimode as well as 2D and 3D initial conditions. This work is sponsored by DOE/NNSA Research Grants DE-FG52-07NA28058 (Stewardship Sciences Academic Alliances) and DE-FG52-04NA00064 (National Laser User Facility). [Preview Abstract] |
Wednesday, November 19, 2008 3:30PM - 4:00PM |
QI1.00002: A High Energy Density Shock Driven Kelvin-Helmholtz Shear Layer Experiment Invited Speaker: In 2002, a high energy density Kelvin-Helmholtz (KH) instability experiment was designed (O.A. Hurricane, \textit{High Energy Density Phys.}, 2008) for the National Ignition Facility (NIF) Early Light experiment. However, the long backlighter delay, required for the experiments success, could not be accommodated by NIF at that time. In early 2008, this experiment proposal was resurrected by our team, the target was fabricated at Livermore with final assembly at the University of Michigan, and then fielded at the Omega laser facility. The data return from the four shots of the experiment series exceeded expectation. In this paper, we describe the theory and simulation behind the experiment design, the unusual target construction, and present the radiographic data from the Omega experiment in raw form and a preliminary analysis of the data. Discussion of the target design theory and simulations focuses on the key role played by baroclinic vorticity production in the functioning of the target and also illuminates the key design parameters. The data shows the complete evolution of large distinct KH eddies, from formation to turbulent break-up. The data appears to graphically confirm a theoretical fluid dynamics conjecture about the existence of supersonic bubbles over the vortical structure [transonic convective Mach numbers (D. Papamoschou and A. Roshko, \textit{J. Fluid Mech.}, \textbf{197}, 1988)] that support localized shocks (shocklets) not extending into the free-stream$^{ }$(P.E. Dimotakis, \textit{AIAA 91-1724}, Proc. 22$^{nd}$ Fluid Dyn., Plasma Dyn., {\&} Lasers Conf., 1991). The consequences of these observations on understanding the turbulent transition, growth-rates and mixing in compressible supersonic turbulent shear layers will be discussed. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. A National Laser Users Facility grant also supported this work. Collaborators: J.F. Hansen$^{\ast }$, E.C. Harding$^{\# }$, R.P. Drake$^{\# }$, H.F. Robey$^{\ast }$, C.C. Kuranz$^{\# }$, B.A. Remington$^{\ast }$, and M.J. Bono$^{\ast }$ ($^{\ast }$Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California, 94551 $^{\# }$U. of Mich., Dept. of Atmospheric, Oceanic and Space Sciences, 2455 Hayward St., Ann Arbor, Michigan, 48109-2143) [Preview Abstract] |
Wednesday, November 19, 2008 4:00PM - 4:30PM |
QI1.00003: Timing of Multiple Shock Waves in Cryogenic-Deuterium Targets Invited Speaker: Achieving ignition and high performance from inertial confinement fusion targets requires optimization of the implosion dynamics. Critical to this is the timing of a sequence of shock waves that are used to condition the shell and fuel as they are imploded. The National Ignition Campaign (NIC) specifications for ignition designs require that these shock waves coalesce at precise intervals that must be controlled to $\sim $50 ps. The plan for ignition includes optimization experiments that use surrogate targets to measure the timing and strength of shocks, then iterating the drive profile to achieve the required precision. These surrogate targets use an ignition-style capsule fitted with a deuterium-filled re-entrant cone embedded in that shell. The shocks are observed in flight through a transparent window using optical diagnostics. We report on OMEGA experiments that demonstrated this shock-timing technique in liquid deuterium driven by hohlraums that reached radiation temperatures of 165 eV. Multiple spherically converging shocks are also being diagnosed and timed in direct-drive deuterium-filled spheres to optimize cryogenic implosions and validate hydrodynamic simulations. This work was supported by U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302. Contributors: V.N. Goncharov, S.X. Hu, M.A. Barrios, D.E. Fratanduono, T.C. Sangster, D.D. Meyerhofer, UR/LLE, P.M. Celliers, D.H. Munro, D.G. Hicks, H.F. Robey, G.W. Collins, O.L. Landen, LLNL, R.E. Olson, SNL. [Preview Abstract] |
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