Bulletin of the American Physical Society
57th Annual Meeting of the APS Division of Plasma Physics
Volume 60, Number 19
Monday–Friday, November 16–20, 2015; Savannah, Georgia
Session UO6: Laboratory Astrophysics |
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Chair: David Martinez, Lawrence Livermore National Laboratory Room: 201/202 |
Thursday, November 19, 2015 2:00PM - 2:12PM |
UO6.00001: Rayleigh Taylor Growth At An Embedded Interface Driven By A Radiative Shock C.M. Huntington, H.-S. Park, K.S. Raman, A.R. Miles, S.A. MacLaren, D.H. Kalantar, H.F. Robey, B.A. Remington, F.W. Doss, J.L. Kline, K.A. Flippo, C.C. Kuranz, W. Wan, R.P. Drake Radiative shocks are those where the radiation generated by the shock influences the hydrodynamics of the matter in the system. Radiative shocks occur during supernovae, as well as during the rebound phase of inertial confinement fusion (ICF) capsules. In the presence of a radiative shock, Rayleigh-Taylor (RT) growth at an unstable interface may be reduced relative to the growth from a purely hydrodynamic system. Using a 325 eV hohlraum on the National Ignition Facility (NIF), we are able to, for the first time, generate a radiative shock that traverses an RT-unstable interface. Because the generation of radiation at the shock front is a strong function of shock velocity ($\propto v^8$), the RT growth in the presence of fast and slow shocks were directly compared. We observe reduced RT spike development when the driving shock is expected to be radiative. The amplitude of the unstable embedded feature was in good agreement with 2D models for both the low-drive (225 eV) and high drive (325 eV) cases. This result has important implications for our understanding of astrophysical radiative shocks, as well as the dynamics of ICF capsules. [Preview Abstract] |
Thursday, November 19, 2015 2:12PM - 2:24PM |
UO6.00002: Accretion Shocks in the Laboratory: Using the OMEGA Laser to Study Star Formation R.P. Young, C.C. Kuranz, C.K. Li, P. Hartigan, D. Froula, G. Fiksel, J.S. Ross, P.-Y. Chang, S. Klein, A. Zylstra, H.W. Sio, A. Liao We present an on-going series of experiments using the OMEGA laser (Laboratory for Laser Energetics) to study star formation. Stars like our Sun experience ``magnetospheric accretion'' during their formation, wherein material from their surrounding accretion disk hurtles to their surface along magnetic field lines, where it forms an ``accretion shock.'' We have created a scaled ``accretion shock'' experiment where a plasma jet collides with a solid block; this is meant to mimic a stream of accreting material colliding with the surface of a young star. Visible image data show a dense shocked region forming that may ``bore into'' the block. We discuss how this may explain observations from young star systems and how the experiment could be further refined. This work is funded by the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas, grant number DE-NA0001840, and by the National Laser User Facility Program, grant number DE-NA0002032. [Preview Abstract] |
Thursday, November 19, 2015 2:24PM - 2:36PM |
UO6.00003: Studies of nuclear reactions relevant to stellar or Big-Bang Nucleosynthesis using ICF plasmas at OMEGA Alex Zylstra, Hans Herrmann, Yongho Kim, Gerry Hale, Mark Paris, Aaron McEvoy, Maria Gatu Johnson, Johan Frenje, Chikang Li, Fredrick Seguin, Hong Sio, Richard Petrasso, Dennis McNabb, Dan Sayre, Jesse Pino, Carl Brune, Andy Bacher, Chad Forrest, Vladimir Glebov, Christian Stoeckl, Roger Janezic, Craig Sangster The $^{\mathrm{3}}$He$+^{\mathrm{3}}$He, T$+^{\mathrm{3}}$He, and p$+$D reactions directly relevant to Stellar or Big-Bang Nucleosynthesis (BBN) have been studied at the OMEGA laser facility using high-temperature low-density `exploding pusher' implosions. The advantage of using these plasmas is that they better mimic astrophysical systems than cold-target accelerator experiments. Measured proton spectra from the $^{\mathrm{3}}$He$^{\mathrm{3}}$He reaction are used to constrain nuclear R-matrix modeling. The resulting T$+^{\mathrm{3}}$He gamma-ray data rule out an anomalously-high $^{\mathrm{6}}$Li production during the Big Bang as an explanation to the high observed values in metal poor first generation stars. The proton spectrum from the T$+^{\mathrm{3}}$He reaction is also being used to constrain the R-matrix model. Recent experiments have probed the p$+$D reaction for the first time in a plasma; this reaction is relevant to energy production in protostars, brown dwarfs and at higher CM energies to BBN. This work was partially supported by the US DOE, NLUF, LLE, and GA. [Preview Abstract] |
Thursday, November 19, 2015 2:36PM - 2:48PM |
UO6.00004: Neutron Generation Simulations of Collisionless Shock Experiments on NIF S.C. Wilks, D.P. Higginson, S.V. Weber, D.D. Ryutov, J.S. Ross, H.-S. Park, F. Fiuza A series of simulations that model recent collisionless shock experiments at the NIF [1] will be presented. In these experiments, two opposing CD plasmas flow into each other, both plasmas arising from lasers hitting planar CD targets separated by 6, 8, and 10mm. Where the plasma flows overlap, a symmetric peak of neutron generation was observed about the mid-plane. When one of the CD foils was replaced by CH, neutron generation was still observed, but with an asymmetry about the mid-plane. The hybrid PIC code LSP [2] is used to model this interaction. Neutron yields, temporal profiles and burn widths obtained from simulation compare favorably with experimental measurements from NTOF and PTOF [3] diagnostics. \\[4pt] [1] S. Ross, et al., this conference (2015).\\[0pt] [2] D. R. Welch, D. V. Rose, B. V. Oliver, and R. E. Clark, Nucl. Instrum. Methods Phys. Res., Sect. A 464, 134 (2001).\\[0pt] [3] H. G. Rinderknecht, M. Gatu Johnson, A. B. Zylstra, N. Sinenian, M. J. Rosenberg, et al., Rev. Sci. Instrum. 83, 10D902 (2012) [Preview Abstract] |
Thursday, November 19, 2015 2:48PM - 3:00PM |
UO6.00005: The generation of bipolar jets of astrophysical relevance using the OMEGA facility P.-A. Gourdain, E.G. Blackman, A. Frank, D.M. Meyerhofer, C.E. Seyler Bipolar astrophysical plasma jets are generated by young stellar objects, active galactic nuclei and proto-planetary nebulae. They are not only born in harsh environments, they can encounter extreme conditions along the way. Recent observations have made apparent that electron physics impacts the overall dynamics of bipolar plasma jets. For instance, the Hall effect together with Ohmic resistivity can change completely the magnetic field structure inside protoplanetary disks and can alter significantly the magneto-rotational instabilities in the inner regions of the disks. The Hall effect plays a critical role in the magnetic polarity of galactic jets. The numerical simulations presented here show how the OMEGA laser can be used to produce bipolar plasma jets with large Reynolds, magnetic Reynolds and Mach numbers. It will also show how electron physics can break the jet symmetry. A discussion will follow on how to generate similar jets using pulsed-power generators. [Preview Abstract] |
Thursday, November 19, 2015 3:00PM - 3:12PM |
UO6.00006: Foreshock magnetic structure ahead of a laser-driven shock wave Robert Crowston, H. Doyle, G. Gregori, J. Meinecke, A.R. Bell, Y. Kuramitsu, H. Takabe, T. Morita, T. Sano, T. Moritaka, Y. Yamura, T. Ishikawa, H. Yoneda, A. Pelka, Nigel Woolsey The Earth's bow shock contains many wave species that propagate upstream from the shock, against the incoming flow. The mechanism by which these waves are produced remains an open problem. Here, we present an experiment for studying one proposed excitation mechanism. A shock is launched by laser irradiation of a carbon pin immersed in a nitrogen gas. A shock forms, propagates parallel to an externally imposed magnetic field and is diagnosed using interferometry, streaked optical emission imaging and a three axis induction coil. Imaging aids establishing the shock conditions and the induction coil data is used to infer the time evolution of magnetic fields. Analysis extracts the frequency, amplitude and polarisation of magnetic waves arriving ahead of the shock. The results are consistent with instabilities and magnetic waves driven by warm electrons generated at the shock mixing with cold electrons. These waves propagate along magnetic field lines, transport energy and matter ahead of the shock ultimately resulting in an extended foreshock consisting of shock-reflected ions and electrons. [Preview Abstract] |
Thursday, November 19, 2015 3:12PM - 3:24PM |
UO6.00007: Microsecond evolution of laser driven blast waves, the influence of shock asymmetries and the resulting development of magnetic fields Eleanor Tubman, R. Crowston, G. Lam, G. Dimoline, R. Alraddadi, H. Doyle, J. Meinecke, J. Cross, R. Bolis, D. Lamb, P. Tzeferacos, D. Doria, B. Reville, H. Ahmed, M. Borghesi, G. Gregori, N. Woolsey The ability to recreate scaled conditions of a supernova remnant within a laboratory environment is of great interest for informing the understanding of the evolution of galactic magnetic fields. The experiments rely on a near point explosion driven by one sided laser illumination producing a plasma, surrounded by a background gas. The subsequent shock and blast waves emerge following an initial ballistic phase into a self-similar expansion. Studies have been undertaken into the evolution of shock asymmetries which lead to magnetic field generation via the Biermann battery mechanism. [1] Here we use the Vulcan laser facility, with targets such as carbon rods and plastic spheres placed in ambient gases of argon, helium or hydrogen, to produce the blast waves. These conditions allow us to study the asymmetries of the shocks using multi-frame imaging cameras, interferometry, and spectroscopy, while measuring the resulting magnetic fields with B-dot probes. The velocity of the shock and the temporal resolution of the asymmetries can be acquired on a single shot by the multi-framing cameras, and comparison with the measured B-dot fields allow for detailed inferences to be made. \\[4pt] [1] J. Meinecke et al., Nature Phys. 10, 520 (2014) [Preview Abstract] |
Thursday, November 19, 2015 3:24PM - 3:36PM |
UO6.00008: Magnetic field amplification and particle acceleration in high Mach number shocks Frederico Fiuza The amplification of magnetic fields is a central ingredient in understanding particle acceleration in supernova remnant shocks. I will present results from multi-dimensional particle-in-cell simulations of shock formation and particle acceleration for different magnetization levels. These first principles simulations, for unprecedented temporal and spatial scales, help bridge the gap between fully kinetic and hybrid modeling. The results show that depending on the magnetization the turbulence responsible for particle injection and acceleration is determined by different processes, which include Weibel and Bell-type instabilities, but also magnetic reconnection. At high Mach numbers both electrons and ions are shown to be efficiently injected and accelerated. I will discuss the importance of these results for current astrophysical models and the possibility of studying these magnetic field amplification and particle acceleration processes in near future high energy density laboratory experiments. [Preview Abstract] |
Thursday, November 19, 2015 3:36PM - 3:48PM |
UO6.00009: Electron Energization Induced by Magnetic Reconnection in Laboratory Laser-Driven Plasmas Samuel Totorica, Tom Abel, Frederico Fi\'uza The potential to study electron energization in laser-driven plasma experiments of magnetic reconnection is studied using two and three dimensional particle-in-cell simulations for realistic laboratory parameters and boundary conditions. It is demonstrated that electrons with energies several orders of magnitude larger than the thermal energy may be produced in plasma conditions currently accessible in the laboratory. Electrons are primarily accelerated by the reconnection electric field and their spectrum is affected by trapping in plasmoids and by the escape from the finite-sized system, giving rise to a non-thermal component with a power-law shape. We identify the optimal conditions for observing electron acceleration in the laboratory and derive a scaling law for the maximum electron energy, paving the way for a new platform for the experimental study of particle acceleration by magnetic reconnection. [Preview Abstract] |
Thursday, November 19, 2015 3:48PM - 4:00PM |
UO6.00010: Electron Weibel Instability Mediated Laser Driven Electromagnetic Collisionless Shock Qing Jia, Kunioki Mima, Hong-bo Cai, Toshihiro Taguchi, Hideo Nagatomo, X.T. He As a fundamental nonlinear structure, collisionless shock is widely studied in astrophysics. Recently, the rapidly-developing laser technology provides a good test-bed to study such shock physics in laboratory. In addition, the laser driven shock ion acceleration is also interested due to its potential applications. We explore the effect of external parallel magnetic field on the collisionless shock formation and resultant particle acceleration by using the 2D3V PIC simulations. We show that unlike the electrostatic shock generated in the unmagnetized plasma, the shock generated in the weakly-magnetized laser-driven plasma is mostly electromagnetic (EM)-like with higher Mach number. The generation mechanism is due to the stronger transverse magnetic field self-generated at the nonlinear stage of the electron Weibel instability which drastically scatters particles and leads to higher energy dissipation. Simulation results also suggest more ions are reflected by this EM shock and results in larger energy transfer rate from the laser to ions, which is of advantage for applications such as neutron production and ion fast ignition. [Preview Abstract] |
Thursday, November 19, 2015 4:00PM - 4:12PM |
UO6.00011: Measurements of laser-driven magnetic fields in quasi-hohlraum geometries Bradley Pollock, D. Turnbull, C. Goyon, S. Ross, W. Farmer, A. Hazi, E. Tubman, N. Woolsey, K. Law, S. Fujioka, J. Moody Magnetic fields of 10-100 T have been produced with a laser-driven scheme using a parallel-plate target geometry, where a laser is directed through a hole in the front plate and irradiates the plate behind it. Hot electrons generated from the rear plate collect on the front plate, creating a voltage difference ($\sim$ 10-100 keV) between them. When the plates are connected via a quasi-loop conductor, this voltage sources current in the range of $\sim$ 0.1-1 MA which produces a magnetic field along the axis of the loop. The field is generated on fast ($\sim$ ns) timescales, and can be scaled by changing the drive laser parameters. Recent experiments at the Jupiter Laser Facility have allowed temporally-resolved measurements of the voltage between the plates with $\sim$ 1 J laser drive. Separate experiments at the Omega EP laser system have allowed direct Faraday rotation (in fused SiO$_{2}$) measurements of the field strength inside the current loop by employing the 4w polarimetry capability of EP. We have also measured the extent and structure of the field with proton deflectometry at EP. The maximum field recorded along the axis of the quasi-loop is $\sim$ 5 T at moderate (100 J) laser drive, and measurements of fringing fields outside the loop at 1 kJ indicate that the field increases to $\sim$ 40 T. These results are compared with modeling to determine the current driven in the target, and infer information about the plasma conditions which sourced the current. This work was performed under the auspices of the United States Department of Energy by the Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344. [Preview Abstract] |
Thursday, November 19, 2015 4:12PM - 4:24PM |
UO6.00012: Analysis of laser-produces jets from locally heated targets Holger Schmitz, Alex Robinson Recent simulations showed that it might be possible to produce a jet by locally heating a foil target with a high intensity laser, so as to produce a single blast wave which then drives jet formation. In contrast to many earlier experimental setups, the jets in this configuration are formed by a two stage process similar to that thought to be responsible for jets from young stellar objects. As the blast wave expands into the ambient medium it creates an inverse conical density structure. This inverse cone focuses the flow into a conically converging flow which then turns into a narrow jet. The realisation of this two step process in an experiment could make it possible to study the formation of stellar jets in the laboratory. We present new results investigating the criteria that lead to the creation of the inverse conical structure and the subsequent jet formation. The localised heating necessary for driving the jet is achieved by guiding the electrons in self generated magnetic fields at resistivity gradients. We present simulations demonstrating the geometries that lead to the localised heating suitable for jet formation. [Preview Abstract] |
Thursday, November 19, 2015 4:24PM - 4:36PM |
UO6.00013: Characterization of magnetic reconnection in the high-energy-density regime B. Qiao, Z. Xu, H.X. Chang, S.Z. Wu, C.T. Zhou, X.G. Wang, X.T. He Magnetic reconnection (MR), breaking and reorganizing the topology of magnetic field dramatically, is a fundamental process observed in many space, laboratory and astrophysical plasmas. In this talk, we report recent investigations on characterization of magnetic reconnection (MR) in the high-energy-density (HED) regime, where the plasma inflow is strongly driven and the total thermal pressure is larger than the magnetic pressure ($\beta >1)$. This extreme regime of MR occurs frequently in astrophysics and recent HED experiments. Comparing the particle-in-cell simulation results for the interactions of colliding laser-produced plasma bubbles with induced anti-parallel and parallel poloidal magnetic fields respectively, the consequences caused by MR are distinguished from those by plasma bubble collisions and two-fluid effects. It is found that the out-of-plane quadrupole magnetic field, bipolar poloidal electric field, plasma heating and even the out-of-plane electric field appear in both cases, which cannot be recognized as evidences of MR here as previously thought. The Lorentz-invariant scalar quantity $D_{e} =\gamma_{e} \mathord{\buildrel{\lower3pt\hbox{$\scriptscriptstyle\rightharpoonup$}}\over {j}} \cdot (\mathord{\buildrel{\lower3pt\hbox{$\scriptscriptstyle\rightharpoonup$}}\over {E}} +\mathord{\buildrel{\lower3pt\hbox{$\scriptscriptstyle\rightharpoonup$}}\over {v}} \times \vec{{B}})$ [$\gamma_{e} =(1-v_{e}^{2} /c^{2})^{-1/2}$ is the Lorentz factor] in the electron dissipation region is proposed as the key sign of MR occurrence in the HED regime. [Preview Abstract] |
Thursday, November 19, 2015 4:36PM - 4:48PM |
UO6.00014: Axial Magnetic Field Compression within Radial Foil Plasma Jets, Experiment and Simulation Tom Byvank, William Potter, Jae Young Chang, Jacob Banasek, John Greenly, Charles Seyler, Bruce Kusse Compression of an axial magnetic field correlates with density hollowing and azimuthal rotation of a plasma jet generated by the COBRA pulsed power machine (1 MA peak current in 100 ns rise time) in a radial foil (15 $\mu $m Al thin disk) configuration. The plasma jet compresses an external 1 T axial magnetic field (Bz) as it collimates along the central z-axis. Experimental measurements use a Bdot magnetic probe placed in the center of the hollow plasma jet. Experimental results show compression of the 1 T Bz field to 2.4 $+$/- 0.3 T. Predictions made by the extended magnetohydrodynamics (XMHD) code, PERSEUS, show a 5.0 $+$/- 0.7 T field at the probe location. We overview physical reasons for the discrepancy between the experimental and simulation magnetic field compression measurements. [Preview Abstract] |
Thursday, November 19, 2015 4:48PM - 5:00PM |
UO6.00015: Results from colliding magnetized plasma jet experiments executed at the Trident laser facility M.J.-E. Manuel, A.M. Rasmus, C.C. Kurnaz, S.R. Klein, J.S. Davis, R.P. Drake, D.S. Montgomery, S.C. Hsu, C.S. Adams, B.B. Pollock The interaction of high-velocity plasma flows in a background magnetic field has applications in pulsed-power and fusion schemes, as well as astrophysical environments, such as accretion systems and stellar mass ejections into the magnetosphere. Experiments recently executed at the Trident Laser Facility at the Los Alamos National Laboratory investigated the effects of an expanding aluminum plasma flow into a uniform 4.5-Tesla magnetic field created using a solenoid designed and manufactured at the University of Michigan. Opposing-target experiments demonstrate interesting collisional behavior between the two magnetized flows. Preliminary interferometry and Faraday rotation measurements will be presented and discussed. This work is funded by the U.S Department of Energy, through the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas, grant number DE-NA0001840. Support for this work was provided by NASA through Einstein Postdoctoral Fellowship grant number PF3-140111 awarded by the Chandra X-ray Center, which is operated by the Astrophysical Observatory for NASA under contract NAS8-03060. [Preview Abstract] |
Thursday, November 19, 2015 5:00PM - 5:12PM |
UO6.00016: Formation of a reconnection layer in colliding supersonic magnetized HED plasmas Lee Suttle, Sergey Lebedev, Jack Hare, George Swadling, Francisco Suzuki-Vidal, Guy Burdiak, Jian Wu, Qingguo Yang, Thomas Clayson, Simon Bland, Nicolas Niasse, Jeremy Chittenden, Nicholas Stuart, Siddharth Patankar, Timothy Robinson, Roland Smith We present experimental results showing the formation and structural development of a magnetic reconnection layer produced by the collision of two counter-streaming, supersonic plasma flows in a quasi-1D geometry. The flows, which are produced by the ablation from a pair of pulsed-power driven inverse wire arrays, are magnetized - carrying oppositely aligned embedded magnetic fields (B $\sim$ 2T) perpendicular to the direction of the flow. Measurements show spatially resolved distributions of the electron density, magnetic field, ion temperature and flow velocity inside the interaction region at several stages throughout its evolution, via laser interferometry, Faraday rotation and Thomson Scattering techniques. [Preview Abstract] |
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