Bulletin of the American Physical Society
2009 APS April Meeting
Volume 54, Number 4
Saturday–Tuesday, May 2–5, 2009; Denver, Colorado
Session L15: High Energy Density Plasmas |
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Sponsoring Units: DPP Chair: Paul Drake, University of Michigan Room: Governor's Square 14 |
Sunday, May 3, 2009 3:30PM - 3:42PM |
L15.00001: Subsonic and Supersonic shear flows in laser driven high-energy-density plasmas E.C. Harding, R.P. Drake, R.S. Gillespie, M.J. Grosskopf, C.C. Kuranz, A. Visco, J.R. Ditmar, Y. Aglitskiy, J.L. Weaver, A.L. Velikovich, O.A. Hurricane, J.F. Hansen, B.A. Remington, H.F. Robey, M.J. Bono, T. Plewa Shear flows arise in many high-energy-density (HED) and astrophysical systems, yet few laboratory experiments have been carried out to study their evolution in these extreme environments. Fundamentally, shear flows can initiate mixing via the Kelvin-Helmholtz (KH) instability and may eventually drive a transition to turbulence. We present two dedicated shear flow experiments that created subsonic and supersonic shear layers in HED plasmas. In the subsonic case the Omega laser was used to drive a shock wave along a rippled plastic interface, which subsequently rolled-upped into large KH vortices. In the supersonic shear experiment the Nike laser was used to drive Al plasma across a low-density foam surface also seeded with a ripple. Unlike the subsonic case, detached shocks developed around the ripples in response to the supersonic Al flow. [Preview Abstract] |
Sunday, May 3, 2009 3:42PM - 3:54PM |
L15.00002: Wall Shocks as Diagnostic Features of High-Energy-Density Experiments F.W. Doss, R.P. Drake, H.F. Robey, C.C. Kuranz Shock tube experiments in which intense heating ahead of the shock is present, by radiation transfer or other mechanisms, can exhibit heating and ablation of the tube material, driving an inwardly directed radial shock, which we call a wall shock. Both the wall shock and its interaction with the experiment's primary shock can be observed. From this interaction, various parameters related to shock speeds and temperatures may be inferred. Because wall shocks may also be driven by laser preheat, they appear not only in experiments containing strongly radiating shocks, but in other laser driven shock experiments. We present several examples of wall shocks obtained in multiple experimental settings and observed by x-ray radiography, computational support generated from the radiation hydrodynamics code HYDRA, and work detailing how shock parameters may be estimated from wall-shock observations. Supported by the DOE National Nuclear Security Administration under the Predictive Science Academic Alliance Program by grant DE-FC52-08NA28616, under the Stewardship Sciences Academic Alliances program by grant DE-FG52-04NA00064, under the National Laser User Facility by grant DE-FG03-00SF22021, and by the Stewardship Science Graduate Fellowship Program. [Preview Abstract] |
Sunday, May 3, 2009 3:54PM - 4:06PM |
L15.00003: Challenges to understanding radiative shocks R.P. Drake, F.W. Doss, B. Fryxell, M.J. Grosskopf, J.P. Holloway, B. van der Holst, C. Huntington, C.C. Kuranz, E.S. Myra, K.G. Powell, I.V. Sokolov, Q.F. Stout, G. Toth, A.J. Visco Shock waves driven above a threshold velocity near 100 km/s become strongly radiative, converting most of the incoming energy flux into radiation. We produce such shock waves in Xe or Ar by using a laser to shock, ionize, and accelerate a Be plate into a gas-filled shock tube. Structure develops in these systems due to both radiative energy transfer and hydrodynamic instability. We are conducting such experiments, implementing a code to model them, and implementing software to assess the predictive capability of the code in our Center for Radiative Shock Hydrodynamics. This presentation will discuss the challenges and show our progress. [Preview Abstract] |
Sunday, May 3, 2009 4:06PM - 4:18PM |
L15.00004: ABSTRACT WITHDRAWN |
Sunday, May 3, 2009 4:18PM - 4:30PM |
L15.00005: Gaussian curves of X-Ray satellites spectra in the L$\alpha$ $_{\rm x}$, L$\alpha$ $_{2}$, L$\beta$ $_{1}$, L$\beta$$_{2}$ and L$\gamma$ region of 3d, 4d and 5d transition elements Surendra Poonia The X-ray satellites L$\alpha \prime $, L$\alpha \prime \prime $, L$\alpha \prime \prime \prime $, L$\alpha \prime \prime \prime \prime $,$_{ }$L$\alpha _{3}$, L$\alpha _{4}$, L$\alpha _{5}$, L$\alpha ^{ix}$, L$\alpha ^{x}$, L$\alpha _{s}$, L$\beta _{1}^{I}$, L$\beta _{1}^{II}$, L$\beta _{1}^{III}$, L$\beta _{1}^{IV}$, L$\beta _{2}^{I}$, L$\beta _{2}^{(b)}$, L$\beta _{2}^{II}$ L$\beta _{2}^{(c)}$, L$\gamma _{1}\prime $, L$\gamma _{2}\prime $, L$\gamma _{2}\prime \prime $ and L$\gamma \prime _{2,3}$ observed in the L-emission spectra in elements with Z = 26 to 92, have been calculated. The energies of various transitions have been calculated by available Hartree-Fock-Slater using the semi-empirical Auger transition energies in the doubly ionized atoms and their relative intensities have been estimated by considering cross - sections of singly ionized 2x$^{-1}$ (x $\equiv $ s, p) states and then of subsequent Coster-Kronig (CK) and shake off processes. In both these processes initial single hole creation is the prime phenomenon. Each transition has been assumed to give rise to a Gaussian line and the overall spectrum has been computed as the sum of these Gaussian curves. The calculated spectra have been compared with the measured satellite energies in L emission spectra. Their intense peaks have been identified as the observed satellite lines. The one to one correspondence between the peaks in calculated spectra and the satellites in measured spectra has been established on the basis of the agreement between the separations in the peak energies and those in the measured satellite energies. Group of transitions under the transition schemes L$_{3}$M$_{x}$-M$_{x}$M$_{4,5}$, L$_{2}$M$_{x}$-M$_{x}$M$_{4,5}$, L$_{3}$M$_{x}$-M$_{x}$N$_{4,5}$ and L$_{2}$M$_{x}$-M$_{x}$N$_{4,5}$ (x $\equiv $ 1-5), which give rise to these satellites have been identified. [Preview Abstract] |
Sunday, May 3, 2009 4:30PM - 4:42PM |
L15.00006: A Comparison of the Nonlinear Least-Squares Fitting and Analysis of the 633.4-nm (1s$_{5} - 2p_{8}$) and 638.3-nm (1s$_{4} - 2p_{7}$) Optogalvanic Spectral Transitions of Neon Kayode Ogungbemi, Prabhakar Misra OG transitions of neon excited in an Iron-neon lamp when illuminated with a Nd: YAG-pumped pulsed dye laser have been investigated, specifically the 1s$_{5}$ -- 2p$_{8}$ and 1s$_{4}$-- 2p$_{7}$ transitions of neon as a function of discharge conditions (0.50-2.00 mA, 5 Torr). The OG waveforms recorded were analyzed using a theoretical model. Monte Carlo least-squares fitting of these waveforms has helped to specifically determine the exponential rates and time constant parameters associated with the evolution of the OG signals. The amplitudes and shapes of these waveforms have been studied as a function of current, and also the effects of collision rates experienced by the neon atoms in the modeling of the cathode plasma. A comparison of the 1s$_{5 }$-- 2p$_{8 }$and 1s$_{4 }$-- 2p$_{7 }$OG transitions of neon provides insight into population distribution and the nature of the collisions occurring in the sustained discharge of the hollow cathode lamp. [Preview Abstract] |
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