Bulletin of the American Physical Society
53rd Annual Meeting of the APS Division of Plasma Physics
Volume 56, Number 16
Monday–Friday, November 14–18, 2011; Salt Lake City, Utah
Session UO8: ICF Simulations and Magneto-inertial Fusion |
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Chair: Tim Collins, Lawrence Livermore National Laboratory Room: Ballroom I |
Thursday, November 17, 2011 2:00PM - 2:12PM |
UO8.00001: Three-Dimensional Distributions of Scattered Light in NIF ``Exploding-Pusher'' Polar-Drive Experiments R.S. Craxton, P.W. McKenty, E.J. Bond, S. Le Pape, A.J. MacKinnon, P.A. Michel, J.D. Moody Backscattered-light distributions recorded on the NIF near-backscatter-imager (NBI) diagnostic, obtained during ``exploding-pusher'' polar-drive experiments\footnote{ A. M. Cok, R. S. Craxton, and P. W. McKenty, Phys. Plasmas \textbf{15}, 082705 (2008).} used for diagnostics commissioning, are presented together with simulations using the hydrodynamics code \textit{SAGE}.\footnote{ R. S. Craxton and R. L. McCrory, J. Appl. Phys. \textbf{56}, 108 (1984).} The simulations include the exact beam directions of all NIF beams. The scattered light is predicted to be strongly peaked in the polar direction, predominantly in the angular range covered by the NBI diagnostics, and subject to 2:1 modulations (peak to valley) in the azumithal direction. Detailed structures seen in the NBI images are reproduced in the simulations, allowing one to identify the individual beams responsible. Comparisons with such simulations can potentially enable the absorption in polar-drive experiments to be diagnosed. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302. [Preview Abstract] |
Thursday, November 17, 2011 2:12PM - 2:24PM |
UO8.00002: 2D and 3D Simulations of Exploding Pusher Capsules Jesse Pino, Andrew Smith, Aaron Miles A research campaign is underway at the National Ignition Facility (NIF) at LLNL to study rapidly evolving, non-LTE, inertial fusion plasmas. The goal is to field thin-shelled, gas filled ``Exploding Pusher'' capsules in a Polar Direct Drive (PDD) configuration. Ion temperatures of $>$ 15 keV and electron temperatures of $>$ 5 keV are reached. A small convergence ratio and rapidly ablated shell reduce susceptibility to hydrodynamic instabilities. Using 1D simulations, most favorable configurations were found to be thin SiO$_2$ or Be shells containing 10 atm of D$_2$-He$^3$ in a 2:1 ratio. This poster describes the 2D and 3D ARES Radiation Hydrodynamics simulations of these capsules. 2D simulations are essential because the PDD configuration requires that each of the beams be ``repointed'' away from their nominal angles. Each beam can also have a separate power profile and focal length. Large ensembles of simulations were run to probe the parameter space and find the optimal pointing resulting in the most spherical implosions. Response surfaces were constructed to ascertain the susceptibility to shot-time fluctuations. We also discuss resolution convergence and present preliminary results of 3D modeling. [Preview Abstract] |
Thursday, November 17, 2011 2:24PM - 2:36PM |
UO8.00003: Thermonuclear burn model within a molecular dynamics simulation of hot dense plasmas James Glosli, Michael Murillo, John Castor, Chris Fichtl, Paul Grabowski, Frank Graziani Applications of classical molecular dynamics methods to dense plasmas preserve the many-body ion-ion correlations functions that many other theoretical approaches neglect. However, a strictly classical description of a hot dense plasma will fail in modeling thermonuclear burn. To rectify this we introduce a model that allows for fusion events, coupling of the ions and electrons and the production of radiation with in a MD framework. The fusion is incorporated though a stochastic process that allows fusion between nearby ions. The probabilities for this process are chosen to reproduce known nuclear cross-section data. The ion-electron coupling model replaces the electrons with a thermal bath, which couples to the ions via a Langevin process. The Langevin parameters are chosen to slow fast ions according to known dE/dx formulae and to drive the electron and ion temperatures toward a common temperature. Finally, the energy flow to and from the radiation field is modeled simply by a set of ode's that couple the electron bath and radiation field. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. [Preview Abstract] |
Thursday, November 17, 2011 2:36PM - 2:48PM |
UO8.00004: Collaborative Comparison of High-Energy-Density Physics Codes M. Fatenejad, C. Fryer, B. Fryxell, D. Lamb, E. Myra, J. Wohlbier We will describe a collaborative effort involving the Flash Center for Computational Science, The Center for Radiative Shock Hydrodynamics (CRASH), LANL, and LLNL to compare several sophisticated radiation-hydrodynamics codes on a variety of HEDP test problems and experiments. Currently we are comparing efforts to simulate ongoing radiative shock experiments being conducted by CRASH at the OMEGA laser facility that are relevant to a wide range of astrophysical problems. The experiments drive a collapsed planar radiative shock through a Xenon-filled shock tube. Attempts to simulate these experiments have uncovered various challenges to obtaining agreement with experimental results. We will present the results of code-to-code comparisons that have enabled us to understand the impact of differences in numerical methods, physical approximations, microphysical parameters, etc. [Preview Abstract] |
Thursday, November 17, 2011 2:48PM - 3:00PM |
UO8.00005: Electron energy transport in Laser Produced Plasmas Using a Velocity Dependent Krook (DVK) Model in one and two dimensions Wallace Manheimer, Denis Colombant We have extended our VDK model for nonlocal electron energy transport to two dimensions, using a simple extension of our one dimensional model. There are various simplifications one can make to reduce the computer time involved in a calculation. For instance, there is often a dominant direction for the heat flow, axial in foil acceleration calculations, and radial in spherical implosion calculations. One option is to consider the VDK model in only the dominant direction. Furthermore, one can apply the VDK model at a subset of points in the transverse (to the dominant) direction and use interpolation. To do a two dimensional calculation, it is possible to use a VDK model independently in each direction. In this model as well, we can employ the VDK model at every point in each direction, or at a subset. [Preview Abstract] |
Thursday, November 17, 2011 3:00PM - 3:12PM |
UO8.00006: ABSTRACT WITHDRAWN |
Thursday, November 17, 2011 3:12PM - 3:24PM |
UO8.00007: Experiments and Simulations of Laser-Driven Magnetized ICF Targets on OMEGA P.-Y. Chang, G. Fiksel, M. Hohenberger, J.R. Davies, J.P. Knauer, R. Betti, F.H. S\'eguin, R.D. Petrasso Recent experiments on OMEGA have shown that magnetizing the hot spot in a laser-driven inertial confinement fusion experiment leads to an enhancement of the implosion performance. A magnetic seed field of 8 T was embedded into a warm plastic (CH) capsule filled with D$_{2}$ gas. The target was imploded in a polar-drive configuration using 40 beams of the OMEGA laser. This resulted in an estimated peak magnetic field of $\sim $20 MG, and a measured 15{\%} and 30{\%} increase of the ion temperature and the fusion yield with respect to unmagnetized targets. To study the magnetic-field topology and its effects on the target, we have implemented a 2-D, azimuthal symmetry MHD subroutine into the 1-D hydrodynamics code \textit{LILAC}. Since the plasma beta is much greater than unity during the implosion, the magnetic field does not affect the implosion dynamics and behaves as a passive variable. We present results from these simulations and compare them to experimental proton radiography data of an imploding, magnetized target. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement Nos. DE-FC52-08NA28302 and DE-FG02-04ER54768. [Preview Abstract] |
Thursday, November 17, 2011 3:24PM - 3:36PM |
UO8.00008: Fusion-Yield Enhancement in Magnetized Laser-Driven Implosions G. Fiksel, P.-Y. Chang, M. Hohenberger, J.P. Knauer, R. Betti, F.J. Marshall, D.D. Meyerhofer, F.H. S\'eguin, R.D. Petrasso We have successfully demonstrated an enhancement of the fusion performance of a magnetized, laser-compressed inertial confinement fusion target. A spherical CH target with a 10-atm D$_{2}$-gas fill was imploded using the OMEGA laser in a polar-drive configuration. A seed magnetic field of 80 kG was embedded in the target, and was subsequently trapped and compressed by the imploding conductive plasma. As a result of the target hot-spot magnetization, the electron-radial heat losses were suppressed and the observed ion temperature and neutron yield were enhanced by 15{\%} and 30{\%}, respectively. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302. [Preview Abstract] |
Thursday, November 17, 2011 3:36PM - 3:48PM |
UO8.00009: High-Yield Magnetized Liner Fusion Explosions and Blast Mitigation Stephen Slutz, Roger Vesey, Michael Cuneo Cylindrical liner implosions with preheated and magnetized deuterium-tritium (DT) are predicted to reach fusion conditions on present pulsed power machines [S.A. Slutz et al Phys. Plasmas 17, 056303 (2010)]. We present simulations indicating that high yields (1-10 GJ) and gains (100-1000) may be possible at currents of about 60-70 MA if a cryogenic layer of solid DT is provided on the inside surface of the metal liner. A hot spot is formed from the central preheated magnetized low-density gas and a burn wave propagates radially into the surrounding cold dense fuel. These yields and gains are more than adequate for inertial fusion energy. However, the pulsed-power driver must be protected from the blast of these high-yield explosions. Numerical simulations are presented which show that the blast can be deflected and the fusion neutrons absorbed by a blanket that partially surrounds the liner. Thus a modest length transmission line can be used to deliver power to the liner. [Preview Abstract] |
Thursday, November 17, 2011 3:48PM - 4:00PM |
UO8.00010: Experimental progress toward magnetized liner inertial fusion on Z Daniel Sinars, Mark Herrmann, Michael Cuneo, Derek Lamppa, Andrew Lopez, Ryan McBride, Dean Rovang, David Hanson, Eric Harding, Charles Nakhleh, Stephen Slutz, Roger Vesey, Adam Sefkow, Kyle Peterson Yields exceeding 100 kJ may be possible on the 25 MA Z facility at Sandia using the implosion of cylindrical metal liners onto magnetized ($>$10 T) and preheated (100-500 eV) deuterium-tritium fuel [S.A. Slutz et al., Phys. Plasmas 17, 056303 (2010)]. The fusion fuel in such targets absorbs about 100 kJ, so a 100 kJ yield would be `scientific breakeven.' Suitable liner targets (Al and Be) have been fabricated and used in experiments on the magneto-Rayleigh-Taylor instability. Magnetic field coil prototypes for $>$10 T axial fields are being tested. Preheat experiments using the multi-kJ Z-Beamlet laser are planned. Cryogenic deuterium fuel systems have been developed. Integrated magnetized liner inertial fusion (MagLIF) tests using deuterium fuel are expected in 2013. [Preview Abstract] |
Thursday, November 17, 2011 4:00PM - 4:12PM |
UO8.00011: Beryllium liner z-pinches for magneto-Rayleigh-Taylor studies on Z R.D. McBride, S.A. Slutz, D.B. Sinars, R.W. Lemke, M.R. Martin, C.A. Jennings, M.E. Cuneo, M.C. Herrmann, B.E. Blue Magnetized Liner Inertial Fusion (MagLIF) [S.A. Slutz, et al., Phys. Plasmas \textbf{17}, 056303 (2010)] is a promising new concept for achieving $>$100 kJ of fusion yield on Z. The greatest threat to this concept is the magneto-Rayleigh-Taylor (MRT) instability. Thus experimental campaigns have been initiated to study MRT growth in fast imploding ($<$100 ns) cylindrical liners. This talk will present results from experiments that used 6.151-keV radiography to study the implosions of unperturbed (surface roughness only) beryllium (Be) liners. The high transmission efficiency of 6.151-keV photons through Be allowed us to obtain radiographs with finite transmission throughout the radial extent of the imploding liners. The data from these experiments will be shown and compared to simulation data from several magneto-hydrodynamic codes. These data are allowing us to evaluate the integrity of the inside (fuel-confining) surface of the imploding liner as it approaches stagnation. [Preview Abstract] |
Thursday, November 17, 2011 4:12PM - 4:24PM |
UO8.00012: Evolution of Thermal Plasma Formed from Thick Aluminum Pulsed with Multi-MG Magnetic Field B.S. Bauer, S. Fuelling, I.R. Lindemuth, R.E. Siemon, K.C. Yates, W.L. Atchison, T.J. Awe, S.F. Garanin, S.D. Kuznetsov Understanding the evolution of ohmically heated conductors is exceptionally important for basic physics and applications. The thermal ionization of the surface of Al-6061 rods with radii larger than the magnetic skin depth has been investigated with well-characterized experiments and detailed numerical modeling. With appropriate rod electrical connections, plasma formation is predominantly a thermal process. Time-resolved imaging, radiometry, spectroscopy, and laser shadowgraphy find plasma forms when the surface magnetic field reaches 2.2 MG. As the pulsed current grows, the visible spectrum shifts from more bremsstrahlung-like to blackbody-like. Radiation-MHD simulations with UP, MHRDR, and Raven are explaining the experimental data, which can be computationally reproduced using certain choices of models for resistivity, equation of state, other transport coefficients, and radiation opacities. [Preview Abstract] |
Thursday, November 17, 2011 4:24PM - 4:36PM |
UO8.00013: The Magnetized Noh Problem as a Verification Test for Z-Pinch Simulation Codes J.L. Giuliani, A.L. Velikovich, J.W. Thornhill, S.T. Zalesak Advanced simulations of high energy density Z-pinch plasmas involve 2D and 3D computer codes. The classic Noh problem of a strong, self-similar expanding shock accreting inflowing gas of constant velocity is often used for verification of hydrodynamic codes. The more relevant test of the M in MHD appropriate for a stagnating pinch are the new, exact, self-similar solutions that extend the Noh problem to include ideal MHD with an azimuthal magnetic and non-uniform velocity profiles for the inflowing gas. This magnetized Noh problem is used to test two R-Z MHD codes, MACH2 and CERBERUS, and the 3D MHD Cartesian code ATHENA. Comparison of the simulations against the self-similar solution shows good agreement for CERBERUS, while the Cartesian code appears subject to a growing instability which can be removed with a diffusive Riemann solver. In summary, the magnetized Noh problem is a new and challenging verification tool for MHD codes designed to model imploding Z pinches. [Preview Abstract] |
Thursday, November 17, 2011 4:36PM - 4:48PM |
UO8.00014: Fusion Based on the Inductively-Driven Lithium Liner Compression of an FRC Plasmoid John Slough, David Kirtley, Richard Milroy A method for achieving the compressional heating required to reach fusion gain conditions based on the compression of a Field Reversed Configuration plasmoid (FRC) is described. An inductive technique is employed to accelerate an array of thin, lithium metal bands radially inward to create a three dimensional compression of the target FRC. The FRC is formed inside the vacuum vessel using a rotating magnetic field generated by antennas located outside the reactor vessel. No ports or opening of the reactor is required during fusion burn. The metal bands can be located several meters from the target implosion site, and with inductive drive the driver coils are physically positioned outside the reactor vacuum wall. The speed and direction of the shells for convergent motion is controlled by appropriately shaped flux concentrators inside the vacuum vessel that also serve as cooling conduits and breeding blankets. An effective fusion blanket is formed with shell convergence absorbing the fusion energy as well as the radiated plasma energy during the brief fusion burn. The resultant vaporized and ionized blanket shell expands compressing the external magnetic field providing for direct energy conversion. Several aspects of the process have been explored experimentally and numerically and a description of a sub megajoule experiment for obtaining fusion breakeven with the FRC will be presented. [Preview Abstract] |
Thursday, November 17, 2011 4:48PM - 5:00PM |
UO8.00015: Planar Foil MRT Instability Measurements Using a 1-MA LTD J.C. Zier, D.A. Chalenski, S.G. Patel, D.M. French, R.M. Gilgenbach, M.R. Gomez, Y.Y. Lau, A.M. Steiner, I.M. Rittersdorf, M.R. Weis, M.G. Mazarakis, M.R. Lopez, M.E. Cuneo Initial dynamic load experiments were performed on UM's 1-MA linear transformer driver (LTD) facility, MAIZE, to characterize magneto-Rayleigh-Taylor (MRT) instability growth and plasma dynamics on planar-foil plasmas. The loads utilized a double current return plate geometry with a 400 nm-thick Al foil positioned between the return plates. Magnetic pressure accelerated the foil plasma to drive MRT instability that was measured using shadowgraphy. Plasma dynamics were observed to be dominated by an initial expansion phase where both foil interfaces were found to be MRT unstable with 85-105 ns e-folding times. [Preview Abstract] |
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