Bulletin of the American Physical Society
2008 APS April Meeting and HEDP/HEDLA Meeting
Volume 53, Number 5
Friday–Tuesday, April 11–15, 2008; St. Louis, Missouri
Session 1HE: Stellar Explosions, Turbulence and Instabilities |
Hide Abstracts |
Sponsoring Units: HEDP HEDLA Chair: Paul Drake, University of Michigan Room: Hyatt Regency St. Louis Riverfront (formerly Adam's Mark Hotel), Promenade F |
Friday, April 11, 2008 8:30AM - 8:55AM |
1HE.00001: HED physics frontiers on OMEGA/OMEGA EP Invited Speaker: The 60 beam, 30 kJ, OMEGA laser facility has been operating at the University of Rochester for more than a decade. The OMEGA EP laser facility adjacent to it will be completed in Q3FY08. OMEGA EP will consist of four beamlines with NIF-like architecture. Each of the beams will ultimately produce 10 ns 6.5 kJ energy ultraviolet pulses directed into the EP target chamber. Two of the beamlines will also operate as high energy petawatt (HEPW) lasers, with up to 2.6 kJ each in 10 ps IR pulses. The HEPW beams can be injected into either the EP chamber or the existing OMEGA target chamber for integrated experiments. This talk will describe the OMEGA EP project status, HED physics possibilities using the combined system, and opportunities for external user access. The full OMEGA laser system (original 60 beam OMEGA and OMEGA EP) will allow unprecedented opportunities for HED physics research. These include backlighting of ICF implosions and integrated Fast Ignition Experiments in the OMEGA target chamber. The configuration flexibility of the OMEGA EP target area, will allow a wide variety of HED physics research, with the possibility of mixing and matching short and long pulse laser beams. Research areas will include episodic jets, the use of up to 40 ns long drive pulses for Equation of State measurements, short pulse, high intensity backlighting of otherwise opaque materials, and the possibility of creating an electron-positron plasma The ongoing OMEGA EP Use Planning process will be described. [Preview Abstract] |
Friday, April 11, 2008 8:55AM - 9:20AM |
1HE.00002: Stellar convection and turbulence Invited Speaker: We give an overview on recent research about turbulent stellar convection. In addition to analytical models there are in particular numerical models being developed at an increasing rate. Such simulations presently consider already rather varied contexts in stellar physics, starting with classical aspects such as solar granulation, attempts to model larger parts of convective envelopes of normal stars or stellar convective cores. They address now even the less classical situation where convection in shells is more directly connected to nuclear burning such as oxygen burning in late stages of the evolution of massive stars. We describe the main features predicted by such models, viz. the general structure of the convective flows, the nature of the turbulent field and overshooting. We will also address model verification and open questions. [Preview Abstract] |
Friday, April 11, 2008 9:20AM - 9:45AM |
1HE.00003: Type II Supernovae Invited Speaker: We give an overview of the hydrodynamics of core collapse supernova explosions according to the results of recent two and three-dimensional numerical simulations. Emphasis is placed on the various hydrodynamic instabilities that occur during both the early and advanced stages of the explosion, and the importance of these instabilities for the interpretation of supernova observations, like spectra, light curves, polarimetry, and inferred pulsar recoils. The Type II supernova SN 1987A in the Large Magellanic Cloud is used as a case study to illustrate these points. [Preview Abstract] |
Friday, April 11, 2008 9:45AM - 10:10AM |
1HE.00004: Laboratory blast wave driven instabilities Invited Speaker: This presentation discusses experiments well-scaled to the blast wave driven instabilities during the explosion phase of SN1987A. Blast waves 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. 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 a perturbed interface, which produces nonlinear, unstable growth dominated by the Rayleigh-Taylor (RT) instability. Recent experiments have been performed using complex initial conditions featuring a three-dimensional interface structure with a wavelength of 71 $\mu $m in two orthogonal directions, at times supplemented by an additional sinusoidal mode of 212 $\mu $m or 424 $\mu $m. We have detected the interface structure under these conditions, using dual orthogonal radiographs on some shots, and will show some of the resulting data. Recent advancements in our x-ray backlighting 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. Current simulations do not show this phenomenon. This presentation will discuss the amount of mass in these spike extensions as well as the error analysis of this calculation. Future experiments will also be discussed. They will be focusing on realistic initial conditions based on 3D stellar evolution models. This research was sponsored by the Stewardship Science Academic Alliances Program through DOE Research Grants DE-FG52-07NA28058, DE-FG52-04NA00064, and other grants and contracts. [Preview Abstract] |
Friday, April 11, 2008 10:10AM - 10:35AM |
1HE.00005: Theory and simulation of astrophysical explosions and turbulence Invited Speaker: Supernova explosions are among the most dramatic in the universe. Type II supernovae follow the core collapse of a massive star, while Type Ia supernovae are typically believed to be thermonuclear explosions of carbon-oxygen white dwarfs that have accreted enough material to initiate carbon burning. In both cases, the explosion dynamics are complicated by hydrodynamic instabilities that make spherical symmetry impossible. Much of the work that is done on hydrodynamic mixing in SNe draws, on the one hand, on the fundamental instability problems of classical Rayleigh-Taylor (RT) and steady-shock Richtmyer-Meshkov (RM), and, on the other hand, on complex (often multiphysics) computational and experimental systems. These include numerical simulations of supernovae and laser-driven laboratory experiments that invoke Euler scaling to make connections to their much larger astrophysical counterparts. In this talk, we consider what additional insight is to be gained from considering a third fundamental instability problem that is more relevant than either RT or RM in isolation and somewhat less complex than the full system. Namely, we consider an idealized blast-wave-driven problem in which a localized source drives a divergent Taylor-Sedov blast wave that in turn drives a perturbed interface between heavier and lighter gamma-law fluids. Within this context, we use numerical simulations and simplified analytic models to consider the effect of the initial perturbation spectrum in determining the late-time asymptotic state of the mixing zone, the interaction of multiple unstable interfaces relevant to core-collapse supernovae, and the proximity of the forward shock to the developing instability. Finally, we discuss how laser-driven laboratory experiments might be used to help resolve some as yet unanswered questions in supernova explosion hydrodynamics. [Preview Abstract] |
Friday, April 11, 2008 10:35AM - 11:00AM |
1HE.00006: Nonlinear evolution of hydrodynamic instabilities from multimode initial perturbation Invited Speaker: The RT and RM hydrodynamic instabilities are subjects of intensive experimental and theoretical research because of its critical importance in inertial confinement fusion and astrophysics research. The nonlinear evolutions of those instabilities in 3D, from an initial multimode perturbation, were study experimentally and theoretically. The RM experiments were performed using the BGU shock tube facility, where the turbulent mixing zone evolution following the passage of shocks through the interface of two different fluids wee measured. The RT experiments were performed using the OMEGA laser facility at LLE, where the bubble size distribution evolution from an initial 3D broadband modulation was measured. The experimental result were compared with the prediction of the bubble-competition and the mode-coupling models, developed to describe the nonlinear evolution of the instability from a multimode initial perturbation, as well as with full 3D numerical simulations. Collaborators: O. Sadot, V. Smalyuk, Y. Elbaz, E. Leionov, A. Formoza, G. Malamud, N. Wygoda, A. L. Levin, G. Ben-Dor, J. A. Delettrez, D. D. Meyerhofer, T. C. Sangster, R. Betti, V. N. Goncharov [Preview Abstract] |
Friday, April 11, 2008 11:00AM - 11:15AM |
1HE.00007: BREAK
|
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700