Bulletin of the American Physical Society
2005 47th Annual Meeting of the Division of Plasma Physics
Monday–Friday, October 24–28, 2005; Denver, Colorado
Session RO2: Simulation of Plasma |
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Chair: John Verboncoeur, University of California, Berkeley Room: Adam's Mark Hotel Governor's Square 11 |
Thursday, October 27, 2005 2:00PM - 2:12PM |
RO2.00001: Grid-Free Lagrangian Plasma Simulations with Dynamic Point Insertion Andrew Christlieb, Benjamin Sonday, Robert Krasny We describe a grid-free Lagrangian particle simulation method for collisionless plasmas. The method is O(N log N) and couples a treecode field solver with a boundary integral method to efficiently solve Poisson's equation without using an underlying mesh [1]. Our previous results were obtained using a fixed number of Lagrangian particles. During a long simulation this eventually leads to lower resolution as gaps appear in the particle distribution. The present approach avoids this problem by adaptively inserting new particles to maintain resolution in phase space. The initial particle position is viewed as a Lagrangian parameter and new particles are inserted using local interpolation from current particles with respect to this parameter [2]. We consider two examples. First we present simulations of charged particle dynamics in a Penning-Malmberg trap and study phenomena such as crystal formation. Next we look at the two stream instability for cold and warm plasmas. Adaptive particle insertion allows one to capture details that are difficult to resolve with traditional particle simulations. \\ REFERENCES \\ 1) Christlieb, A.J., Krasny, R., Verboncoeur, J.P. (2004) Comp. Phys. Comm., vol 164 p. 306 \\ 2) Lindsay, K., Krasny, R. (2001) J. Comput. Phys., vol. 172, p. 879 [Preview Abstract] |
Thursday, October 27, 2005 2:12PM - 2:24PM |
RO2.00002: Equation-free Modeling of Ion Acoustic Wave with Particle Trapping George Stantchev, Michael Shay, William Dorland, James Drake Recently, Shay et al.[1] have successfully implemented equation-free projective integraion methods to simulate the propagation and steepening of a 1D ion acoustic wave. For the forward extrapolation step they have been using only a small number of lower moments of the probability density function (PDF) based on the assumption that the distribution would remain Maxwellian at all times. This however is no longer valid in many interesting situations, in particular for the case of particle trapping. To solve this problem we propose a generalization of Shay's algorithm to allow for tracking of an arbitrary PDF. We estimate the PDF at each micro-time step using statistical wavelet analysis. The resulting vectors of wavelet coefficents are used for forward extrapolation in time to obtain a multi-scale representation of the projected PDF after a coarse time step. An optimal wavelet basis is selected through adaptive refinement at the beginning of each microscopic simulation sequence. We discuss the application of this technique to the 1D acoustic wave problem with particle trapping. \par\noindent [1] M. Shay, J. Drake, W. Dorland, Multiscale modeling of plasmas via equation-free projective integration, in preparation [Preview Abstract] |
Thursday, October 27, 2005 2:24PM - 2:36PM |
RO2.00003: Mesoscale Simulation of Nanoparticle Production Gianluca Zuccaro, Giovanni Lapenta, Giovanni Maizza We present a model to study complex physical systems composed by a set of clusters of different chemical species immersed in a matrix with which they interact. The overall model describes the transient of the basic mechanisms governing the processes of interaction in a two-dimensional micrometer size system. At each time step, the continuum (micrometer scale) model computes the macroscopic fields according to the prescribed boundary conditions. The continuum system is discretized with a desired number of uniform computational cells. Each cell contains a number of computational particles which represent the actual particles mixture. The particle-in-cell (discrete) model maps the macroscopic fields from the (continuum) cells to the particles. A molecular dynamics approach is used for computing the chemical reactions among the particles. We present results of a recent application of this approach to the simulation of nanoparticles formation in SHS reactors [1]. \newline [1] G. Zuccaro, G. Lapenta, G. Maizza, Computer Phys. Commun., 162, 89 (2004). [Preview Abstract] |
Thursday, October 27, 2005 2:36PM - 2:48PM |
RO2.00004: Intermittency in magnetohydrodynamic turbulence: DNS and Lagrangian averaged modeling Jonathan Graham, Pablo Mininni, Annick Pouquet, Darryl Holm The range of scales encountered in MHD problems of astrophysical interest is well beyond expected computer resolutions in the next decades. For this reason, closure schemes are often employed to model the effect of the unresolved scales. One such closure is Lagrangian-averaged magnetohydrodynamics (LAMHD) or the ``alpha model.'' This model is an extension of the smoothing procedure in fluid dynamics which filters velocity fields locally while leaving their associated vorticities unsmoothed, and has proven useful for high Reynolds number turbulence computations. It differs from large eddy simulations in that it preserves the invariants of a given flow. We present DNS and LAMHD simulations of forced and free decaying two-dimensional magnetohydrodynamic turbulence. The exponents of structure functions of the velocity, the magnetic field, and the Els\"asser variables are studied. LAMHD is found to have the same intermittent behavior as the DNS. The statistics of sign cancellations of the current (and vorticity) at small scales are also studied using both the cancellation exponent and the fractal dimension of the structures. LAMHD is found to have the same scaling behavior between positive and negative contributions as the DNS. At large Reynolds numbers, an independence of the cancellation exponent with the Reynolds numbers is observed. [Preview Abstract] |
Thursday, October 27, 2005 2:48PM - 3:00PM |
RO2.00005: Fast Electron Transport with Ionization Effects and Proton Acceleration Alex Robinson, Tony Bell, Robert Kingham In ultraintense laser-solid interactions ($> 10^{18}\mbox{Wcm}^{-2}$), two of the phenomena of great interest are the absorption of laser energy into relativistic electrons and the emission of multi-MeV protons from the back of the target. We have studied both the role of ionization in fast electron transport, and the electrostatic acceleration of protons using kinetic simulation. We have developed a version of the Vlasov-Fokker-Planck code KALOS that includes ionization processes for studying fast electron transport. We have studied the propagation of fast electrons into an un-ionized carbon target. We find that ionization affects the electric field structure. This may have consequence for magnetic field generation in 2D and 3D. We have also developed a three species relativistic Vlasov solver for studying proton acceleration. We have studied the effect of varying the proton density of the target. The Gurevich-Mora model is good at high density, whereas at low proton density the maximum proton energy is reduced, and a definite peak in the spectrum is produced at the highest energy. [Preview Abstract] |
Thursday, October 27, 2005 3:00PM - 3:12PM |
RO2.00006: Polar Direct Drive on the National Ignition Facility S. Skupsky, R.S. Craxton, F.J. Marshall, R. Betti, T.J.B. Collins, R. Epstein, V.N. Goncharov, I.V. Igumenshchev, J.D. Keller, J.A. Marozas, P.W. McKenty, P.B. Radha, J.D. Kilkenny, D.D. Meyerhofer, T.C. Sangster, R.L. McCrory Target designs to achieve direct-drive ignition on the NIF using the x-ray-drive beam configuration are examined. This approach, known as polar direct drive (PDD), achieves the required irradiation uniformity by repointing some of the beams toward the target equator, and by increasing the laser intensity at the equator to compensate for the reduced laser coupling from oblique irradiation.\footnote{ S. Skupsky \textit{et al}., Phys. Plasmas \textbf{11}, 2763 (2004).}$^{,}$\footnote{ R. S. Craxton and D. W. Jacobs-Perkins, Phys. Rev. Lett. \textbf{94}, 095002 (2005); R. S. Craxton \textit{et al}., Phys. Plasmas \textbf{12}, 056304 (2004).}$^{ }$ Techniques to increase the equatorial intensity can include using phase plates that produce elliptical spot shapes, increasing the power in beams directed toward the equator, and using a ring offset from the equator to redirect rays toward the target normal. The requirements for beam pointing and power balance are examined. The simulations use the 2-D hydrocode \textit{DRACO} with a 3-D ray trace to model the laser irradiation and Monte Carlo alpha-particle transport to model the thermonuclear burn. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-92SF19460. [Preview Abstract] |
Thursday, October 27, 2005 3:12PM - 3:24PM |
RO2.00007: Hot Spot Formation in ICF Ignition Targets D.M. Eklund, N.B. Meezan, J.C. Zier, L.J. Suter We present an analysis of hot spot formation physics in an indirect-drive, copper-doped beryllium ignition capsule for the National Ignition Facility. The capsule is simulated in 1-D using the radiation-hydrodynamics code \textsc{hydra}. We find that the initial density of the DT fuel gas affects the early-time formation of the hot spot. As the fuel gas is compressed, thermal conduction and alpha-particle deposition ablate DT ice into the hot spot. A constant-entropy model of the hot spot fuel provides an upper bound on capsule performance as a function of final hot-spot mass. The amount of ablated DT ice affects the ability of the hot spot to reach the temperature and column density necessary for ignition. We apply our understanding of hot-spot formation to quantify the robustness of fusion capsules. Surprisingly, the capsule yield is fairly insensitive to large changes in hot-spot thermal conductivity. This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48. [Preview Abstract] |
Thursday, October 27, 2005 3:24PM - 3:36PM |
RO2.00008: 1 MJ National Ignition Facility Capsule-Hohlraum Studies Paul Bradley, Douglas Wilson Recent plans for ignition on the National Ignition Facility (NIF) call for the first ignition attempt to utilize about 1 megajoule (MJ) of laser energy. We have been working on 2-D capsule-hohlraum implosion calculations for the NIF that utilize a laser drive pulse that peaks at 300 eV and uses less than 1 MJ of energy. We base our design on the H/He gas filled hohlraums that predict successful ignition at 1.8 MJ (1.35 MJ in the calculation). We start our effort with a 0.3 atom{\%} uniformly Cu doped beryllium ablator capsule that has an inner ice radius of 753 $\mu $m, and inner ablator radius of 825 $\mu $m, and an outer ablator radius of 1000 $\mu $m. The baseline hohlraum has a diameter of 5.02 mm and a length of 8.56 mm. After describing the conditions required for our best yield, we will also describe our sensitivity studies to changes in the laser pulse for shock timing and different pointing positions of the inner and outer laser cones for symmetry control.This work performed under the auspices of the U.S. Department of Energy by Los Alamos National Laboratory under Contract W-7405-ENG-36. [Preview Abstract] |
Thursday, October 27, 2005 3:36PM - 3:48PM |
RO2.00009: Hard X-ray and Hot Electron Environment in Vacuum Hohlraums at NIF* Joseph McDonald, L.J. Suter, O.L. Landen, J.M. Foster, J.R. Celeste, J.P. Holder, E.L. Dewald, M.B. Schneider, D.E. Hinkel, R.L. Kauffman, L.J. Atherton, R.E. Bonanno, S.N. Dixit, D.C. Eder, C.A. Haynam, D.H. Kalantar, A.E. Koniges, F.D. Lee, B.J. MacGowan, K.R. Manes, D.H. Munro, J.R. Murry, M.J. Shaw, R.M. Stevenson, T.G. Parham Time resolved hard x-ray images (\textit{hv} $>$ 9 keV) and time integrated hard x-ray spectra (\textit{hv} = 18-150 keV) from vacuum hohlraums irradiated with four 351 nm wavelength NIF laser beams are presented as a function of hohlraum size and laser power and duration. The hard x-ray images and spectra provide insight into the time evolution of the hohlraum plasma filling and the production of hot electrons. The fraction of laser energy detected as hot electrons (F$_{hot})$ is compared with previous measurements, explained by an empirical hohlraum plasma filling model, and compared to radiation-hydrodynamics simulations based on laser-plasma interaction theory. In addition, the significance of Au K-alpha emission and Au K-shell reabsorption observed in some of the bremsstrahlung dominated spectra is discussed. *This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-ENG-48. [Preview Abstract] |
Thursday, October 27, 2005 3:48PM - 4:00PM |
RO2.00010: WITHDRAWN--Molecular dynamics simulations of transport in highly asymmetric plasma mixtures: Application to double-shell ignition targets Sorin Bastea, Harry Robey, Peter Amendt Dense plasma mixtures are often encountered in the study of inertial confinement fusion (ICF) and in many astrophysical environments. Evaluating the associated transport coefficients is important for understanding the performance of ICF targets, in particular double-shell ignition target designs [1]. However, such an assessment is often very difficult when the mixed plasma is highly asymmetric in charge and mass, as in the DT fuel and Au pusher of an ignition double shell. We present molecular dynamics simulation results [2] for the viscosity and mutual diffusion of a DT/Au mixture after deceleration onset, modeled as a binary ionic mixture. Compared with previous one-component plasma models [3], the predicted viscosity and mutual diffusivity are considerably higher and tend to reduce the Rayleigh-Taylor instability growth rates based on the model of Duff, Harlow and Hirt [4]. Mode cutoffs near 10$^{3}$ are predicted on the fuel-pusher interface, leading to the prospect of realistic multimode simulations of instability growth. [1[ P. Amendt et al., Phys. Plasmas \textbf{9}, 2221 (2002). [2] S. Bastea, Phys. Rev. E \textbf{71}, 056405 (2005). [3] J.G. Cl\'{e}rouin, M.H. Cherfi, G. Z\'{e}rah, Europhys. Lett. \textbf{42}, 37 (1998). [4] R.E. Duff, F.H. Harlow, C.W. Hirt, Phys. Fluids \textbf{5}, 417 (1962). This work was performed under the auspices of the U.S. Department of Energy by the University of California Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48. [Preview Abstract] |
Thursday, October 27, 2005 4:00PM - 4:12PM |
RO2.00011: Correlation Effects and their Impact on Line Broadening in Plasmas: Application to $H_\alpha$ Evgeny Stambulchik, Dimitri Fisher, Yitzhak Maron, Hans R. Griem, Spiros Alexiou In the last two decades, several computational approaches to the Stark broadening in plasma have been developed, where motion of both ions and electrons is simulated and their fields are calculated using an effective Debye-Yukawa potential. Such an approximation, in general, can be questioned in cases when the number of plasma particles in the Debye sphere is about unity or below. For testing the applicability of this approach, large-scale molecular-dynamics simulations were performed, with all plasma particles interacting by the Coulomb potential, and the correlations in the motion of the particles were analyzed. It was found that even for a moderately coupled plasma ($n_e = 10^{18}~\mbox{cm}^{-3}$, $T = 1~\mbox{eV}$), the collective effects play a major role in the statistical and dynamical properties of the micro-fields. Nevertheless, the corrections to the $H_\alpha$ profile are rather minor, for which an explanation is presented. [Preview Abstract] |
Thursday, October 27, 2005 4:12PM - 4:24PM |
RO2.00012: Studies of High Energy Density Matter Including Strongly Coupled Plasmas Using Intense Heavy Ion Beams at the GSI Darmstadt and Future FAIR Accelerator Facilities Naeem Tahir, Claude Deutsch, Vladmir Fortov, Viktor Gryaznov, Dieter Hoffmann, Igor Lomonosov, Roberto Piriz, Alexander Shutov, Peter Spiller, Mauro Temporal, Serban Udrea, Dmitry Varentsov Detailed numerical simulations and analytic work have shown that an intense heavy ion beam that will be generated at the future FAIR facility at Darmstadt, that will have an intensity of 2$\;\times\;$10$^{12}$ uranium ions per bunch with a bunch length of 50 ns and a particle energy of 0.4~-~2.7~GeV/u, will be a very efficient tool to create high-energy-density (HED) states in matter including strongly coupled plasmas. These theoretical studies have shown that using this ion beam one will be able to study those regions of the phase diagram that are either very difficult to access or are even unaccessible using the traditional methods of shock compression. [Preview Abstract] |
Thursday, October 27, 2005 4:24PM - 4:36PM |
RO2.00013: Self-Adaptive Event-Driven Simulation of Multi-Scale Plasma Systems Yuri Omelchenko, Homayoun Karimabadi Multi-scale plasmas pose a formidable computational challenge. The explicit time-stepping models suffer from the global CFL restriction. Efficient application of adaptive mesh refinement (AMR) to systems with irregular dynamics (e.g. turbulence, diffusion-convection-reaction, particle acceleration etc.) may be problematic. To address these issues, we developed an alternative approach to time stepping: self-adaptive discrete-event simulation (DES). DES has origin in operations research, war games and telecommunications. We combine finite-difference and particle-in-cell techniques with this methodology by assuming two caveats: (1) a local time increment, \textit{dt} for a discrete quantity $f$ can be expressed in terms of a physically meaningful quantum value, \textit{df}; (2) $f$ is considered to be modified only when its change exceeds \textit{df}. Event-driven time integration is self-adaptive as it makes use of \textit{causality} rules rather than \textit{parametric }time dependencies. This technique enables asynchronous flux-conservative update of solution in accordance with local temporal scales, removes the curse of the global CFL condition, eliminates unnecessary computation in inactive spatial regions and results in robust and fast parallelizable codes. It can be naturally combined with various mesh refinement techniques. We discuss applications of this novel technology to diffusion-convection-reaction systems and hybrid simulations of magnetosonic shocks. [Preview Abstract] |
Thursday, October 27, 2005 4:36PM - 4:48PM |
RO2.00014: FSML - Fusion Simulation Markup Language for Interoperability of Data and Analysis Tools Svetlana Shasharina, Chuang Li The fusion community becomes more interconnected and problems become more complex. This requires the internetworking of various codes, comparing solutions from multiple solvers, and sharing of data and data analysis tools. However, the data formats and data analysis tools used in simulations are highly heterogeneous. Imposing one standard data format and one type of tools is unrealistic due to historical and practical reasons. In this paper, we introduce the Fusion Simulation Markup Language, or FSML - an XML based system for describing and accessing fusion and plasma physics simulation data of various formats used in the fusion community. The system consists of syntactic and semantic metadata organized in specialized XML schemas and APIs written for accessing data from major data analysis and visualization tools. We present the preliminary results, using a subset of MHD variables, and demonstrate their application for two large three-dimension fusion simulation codes M3D and NIMROD. The FSML schema is being extended to include all fundamental MHD variables and other simulations metadata. Comprehensive modules for 3D visualization are being augmented with a set of tools for data interpolation. Finally, FSML is being extended with common API's for accessing data on structured and unstructured meshes. [Preview Abstract] |
Thursday, October 27, 2005 4:48PM - 5:00PM |
RO2.00015: Modernization and Componentization of Fusion Modules for Future Integrated Modeling Ovsei Volberg, Sveta Shasharina, Johan Carlsson We discuss the development of the Framework for Modernization and Componentization of Fusion Modules, which contains a set of tools, standards and techniques for modernization of modules extracted from established fusion codes with subsequent conversion of these modules to components in accordance with modern software engineering practices. The National Transport Code Collaboration (NTCC) project created a community-owned library of modules for integrated fusion modeling. The standards enforced for these modules and strict review process make this library a valuable asset for plasma simulation. Component based approach addresses the modeling of complex, mutually interacting, computationally intensive systems via its reformulation as a problem of coupling between sub-systems designated as components. A certain challenge in developing such components from legacy codes could be addressed by Common Component Architecture (CCA) tools. We report on the results of our application of CCA tools to the development of components from two NTCC modules, GLF23 and MMM95, and coupling them with another component made from the new nonlinear solver. We also report on the comparison of the NTCC standards with the standards of several community-wide projects for integrated modeling in the other areas of science. [Preview Abstract] |
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