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 TO6: Fast Ignition - Simulations |
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Chair: Scott Wilks, Lawrence Livermore National Laboratory Room: Ballroom G |
Thursday, November 17, 2011 9:30AM - 9:42AM |
TO6.00001: Simulations of Implosion and Core Heating for Integrated Cone-in-Shell Fast-Ignition Experiments on OMEGA A.A. Solodov, K.S. Anderson, W. Theobald, R. Betti, J.F. Myatt, C. Stoeckl Integrated cone-in-shell fast-ignition experiments on OMEGA will benefit from improved performance of the OMEGA EP laser, including higher contrast, higher energy, and a smaller focus. A new target design will be used with a low-$Z$ aluminum cone tip, which is expected to significantly reduce the scattering losses of the fast electrons. Resistive magnetic-field collimation will be employed by shaping the cone tip toward the target center. The electrical resistivity mismatch between the Al tip and the surrounding CD plasma can collimate fast electrons into the assembled fuel. The performance of the new target design is investigated using integrated two-dimensional hydrodynamic simulations of implosion and hybrid-PIC simulations of electron transport. The hydrocode \textit{DRACO} simulates the compression of cone-in-shell targets and the hybrid-PIC code \textit{LSP} simulates the transport of fast electrons through the cone tip to the compressed core. Energy deposition of fast electrons in the assembled fuel is investigated. Core heating and neutron yield are computed. 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-FC02-04ER54789. [Preview Abstract] |
Thursday, November 17, 2011 9:42AM - 9:54AM |
TO6.00002: ICF Fast Ignition with Ultra-Relativistic Electron Beams Claude Deutsch, Jean-Pierre Didelez In contradistinction to mean-stream fast ignition scenario, based on collisional stopping in the compressed DT-fuel of relativistic electron beams(REB) in the 1-2 MeV energy range(ER) [1], we consider an ultra-relativistic extension of the Malkin-Fisch [2] attempt at using REB in the several tenths of MeV ER, and stopping them in target through strong induced Langmuir turbulence. We first stress the substantial and inelastic stopping arising from electron-positron pairs(Trident process). Above 100 MeV ER, bremsstrahlung and hard Gammas turn significant(cone scenario). We focus specifically on D and T nuclei electro disintegrating firstly in nucleons, and thereafter with negative pion production included. Then, it appears attractive to envisage pion-catalyzed DD,TT and DT fusion in a very dense and hot plasma surrounding with reduced alpha-sticking. The claim gets supports from the many available Debyelike multiatomic plasma orbitals involving D and T nuclei, pions and eventually electrons. A careful balance of the many collective(turbulent) and nonhadronic inelastic nuclear channels concludes the evaluation of such an approach to REB-driven scenarii for ICF fast ignition.\\[0pt] [1] C Deutsch, H Furukawa, K Mima, M Murakami and K Nishihara, PRL 77,2483(1996) and K V Starikov and C Deutsch PoP 14,022704 (2007) [2] V N Malkin and N J Fisch PRL 89, 125004 (2002) [Preview Abstract] |
Thursday, November 17, 2011 9:54AM - 10:06AM |
TO6.00003: Interaction of intense multi-picosecond laser pulses with matter Andreas Kemp, Laurent Divol, Bruce Cohen We present new results on the two- and three-dimensional kinetic modeling of short-pulse laser-matter interaction of Petawatt pulses at the spatial and temporal scales relevant to current experiments. We address key questions such as characterizing the multi-picosecond evolution of the laser energy conversion into hot electrons, i.e., conversion efficiency as well as angular- and energy distribution; the impact of return currents on the laser-plasma interaction; and the effect of self-generated electric and magnetic fields on electron transport. We will report applications to current experiments at LLNL's Titan laser and Omega EP, and to a Fast-Ignition point design. [Preview Abstract] |
Thursday, November 17, 2011 10:06AM - 10:18AM |
TO6.00004: Magnetic, Material and Geometric Focusing Aids in Hot Electron Driven Fast Ignition R.J. Mason, R.J. Faehl, R.C. Kirkpatrick We study the effects of B-fields, material interfaces and resistivity on the focusing of hot electrons in various target geometries using the implicit hybrid simulation code ePLAS. The model deposits laser light near critical and generates a hot electron component, either fluid or particle, that moves through \textit{E {\&} B}-fields computed by the implicit moment method [1], while dragging on the ``cold'' background electrons and scattering off the local ions. Picosecond pulses at $\sim $10$^{20}$ W/cm$^{2}$ can produce highly divergent electron emission in Cu foils and in pre-pulsed cone targets [2]. We examine the influence of spontaneous and/or external $B-$fields, resistivity and density changes at target interfaces. We study how target contouring and the pulse history might be optimally configured to aid re-focusing of the hot electron energy for more localized target heating. We compare results for fixed Atomic Number with those from variable Z values determined from the Sesame EOS tables.\\[4pt] [1] R. J. Mason, J. Comp. Phys. \textbf{71,} 429 (1987)\\[0pt] [2] R. J. Mason, PRL \textbf{96,} 035001 (2006). [Preview Abstract] |
Thursday, November 17, 2011 10:18AM - 10:30AM |
TO6.00005: A new type of hybrid code for fast-electron transport with hydrodynamic response Robert Kingham, Brennig Williams We present a new hybrid code, relevant to fast-ignition, with PIC fast-electrons coupled to a Vlasov-Fokker-Planck (VFP) background plasma. Using the VFP code {\small IMPACT} [1] for the plasma provides a more complete Ohm's law \& heat-flow description than fluid models, conventionally used. Transport in the plasma includes magnetization effects \& non-local effects when the background is driven hard by the beam. Phenomena such as Nernst advection of B-fields, resistive \& $\nabla{n}\times\nabla{T}$ B-field generation are included. The code also includes ionization. As it is a hybrid code, several picosecond timescales are easily achievable. This makes the code well suited to study the effects of hydrodynamics on fast-electron transport [2], such as re-collimation of the beam due to PdV cooling in the background plasma [3]. The code has been tested against relevant beam-plasma instabilities and is being used to study systems with parameters relevant to FI. We present new results of fast-electrons travelling though a solid density background with hydrodynamic response. \\[4pt] [1] Kingham RJ \& Bell AR, JCP {\bf 194}, 1(2004)\\[0pt] [2] Bush IA {\em et al.}, PPCF {\bf 52} 125007 (2010)\\[0pt] [3] Kingham RJ {\em et al.}, J. Phys.: Conf. Ser. {\bf 244} 022042 (2010) [Preview Abstract] |
Thursday, November 17, 2011 10:30AM - 10:42AM |
TO6.00006: Full-scale PIC simulations of fast ignition Luis O. Silva, Frederico Fiuza, Michael Marti, Ricardo A. Fonseca, John Tonge, Josh May, Warren B. Mori Fast ignition modeling presents a grand challenging due to the different spatial and temporal scales. Following the work on a optimized hybrid algorithm for modeling inhomogeneous plasmas by B. Cohen et al. [JCP 229, 4591 (2010)], an hybrid algorithm was implemented in OSIRIS [F. Fiuza et al., PPCF 53, 074004 (2011)], allowing for the self-consistent modeling of all the relevant physics at different scales, and leading to a dramatic change in the computational resources required to model fast ignition. We will present results from the first multi-dimensional full-scale integrated simulations of fast ignition. Realistic compressed target profiles obtained from hydrodynamic simulations were used to study key questions such as the multipicosecond evolution of laser absorption and beam divergence, the fast electron transport, and its energy deposition in a fully self-consistent manner. Control of electron divergence, capable of providing laser to core energy efficiencies consistent with ignition conditions, will be shown either by changing the laser profile or by using external collimating structures. [Preview Abstract] |
Thursday, November 17, 2011 10:42AM - 10:54AM |
TO6.00007: PIC modeling of material dependence on fast electron generation and transport R. Mishra, M.S. Wei, S. Chawla, Y. Sentoku, R.B. Stephens, F.N. Beg 2D collisional PIC simulations, using PICLS\footnote{Y Sentoku, JCP 227, 6846 (2008)} code that includes dynamic ionization and radiation cooling, are performed to model a recent experiment\footnote{S Chawla et al, this meeting} on the Titan laser using multi-foil targets, where 2x reduction in total fast electron flux and a smaller spot size through high-Z layer were observed. Modeling show that a thin high-Z transport layer (e.g., Au) near lower Z source layer introduces a collimating effect on fast electron transport. Strong self-generated resistive B-fields are produced inside Au layer and at the interface (Al/Au), which confine the fast electron propagation and can also trap electrons in wing region to inhibit their propagation. In addition, effects of the surface material on LPI produced fast electron source characteristics are examined in both planar and buried cone geometries. [Preview Abstract] |
Thursday, November 17, 2011 10:54AM - 11:06AM |
TO6.00008: Cone Material Dependence of Fast Ignition Core Heating Tomoyuki Johzaki, Atsushi Sunahara, Yasuhiko Sentoku, Hideo Nagatomo, Kunioki Mima In cone-guiding fast ignition, the cone material affects the heating performance through the fast electron generation and transport processes [1]. In the present paper, we advanced the research on the cone material dependence of core heating properties with a help of the integrated simulations. By assuming Au, Cu and DLC as the cone material, first we evaluate the pre-plasma generation by radiation-hydro simulations. Using those pre-plasma profiles, the fast electron generation is evaluated by PIC simulations including collision and ionization processes. Then, the fast electron transport is calculated by Fokker-Planck code. In addition to the fundamental feature of cone material dependence, we will discuss the fast electron guiding by self-generated and externally-applied magnetic field, and also radiation effects.\\[4pt] [1] T. Johzaki, et al., Plasma Phys. Control. Fusion 51 (2009) 014002. [Preview Abstract] |
Thursday, November 17, 2011 11:06AM - 11:18AM |
TO6.00009: Reduction of pre-formed plasma inside a cone target for fast ignition Atsushi Sunahara, Tomoyuki Johzaki, Hideo Nagatomo, Hiroyuki Shiraga Reduction of pre-formed plasma inside a cone target for fast ignition of inertial confinement fusion is a crucial problem, since the number of fast electrons that heat the imploded core is reduced by the interaction of short pulse laser with the pre-formed plasma [1]. Three causes for generation of pre-formed plasma are considered; (1) existence of pre-pulse of short pulse laser, (2) break-through of shock wave from the implosion plasma in the cone tip, and (3) simultaneous occurrence of (1) and (2). To suppress cause (2), in particular, we propose pointed cone tips. To investigate propagation of the shock wave from an imploding core to the interior of the pointed cone tip of the cone target, we have conducted 2D radiation hydrodynamic simulations for a variety of materials and cone shapes. Our simulation results show that the optimized pointed cone tip can delay the shock traveling time through the Al pointed cone tip, by 20-30 ps in the typical implosion condition of FIREX experiment at the institute of laser engineering Osaka University. We will present our optimized design of the pointed cone tip.\\[4pt] [1] H. B. Cai, K. Mima, A. Sunahara, T. Johzaki, H. Nagatomo, S. Zhu and X. T. He, Phys. Plasmas, 17, (2010) 023106-1-8. [Preview Abstract] |
Thursday, November 17, 2011 11:18AM - 11:30AM |
TO6.00010: Particle-in-cell simulations with charge-conserving current deposition on graphic processing units Chuang Ren, Xianglong Kong, Michael Huang, Viktor Decyk, Warren Mori Recently using CUDA, we have developed an electromagnetic Particle-in-Cell (PIC) code with charge-conserving current deposition for Nvidia graphic processing units (GPU's) (Kong et al., Journal of Computational Physics 230, 1676 (2011). On a Tesla M2050 (Fermi) card, the GPU PIC code can achieve a one-particle-step process time of 1.2 - 3.2 ns in 2D and 2.3 - 7.2 ns in 3D, depending on plasma temperatures. In this talk we will discuss novel algorithms for GPU-PIC including charge-conserving current deposition scheme with few branching and parallel particle sorting. These algorithms have made efficient use of the GPU shared memory. We will also discuss how to replace the computation kernels of existing parallel CPU codes while keeping their parallel structures. [Preview Abstract] |
Thursday, November 17, 2011 11:30AM - 11:42AM |
TO6.00011: LSP simulations of the effect of scattering on hot electron transport A.G. Krygier, S. Jiang, V. Ovchinnikov, D.W. Schumacher, R.R. Freeman, A. Link Characterization of the hot electron source in ultra-intense laser-plasma interactions (LPI) is important to fast ignition. The transport of hot electrons in plasma involves self-generated fields and scattering which modify the electron transport. The apparent divergence of the electrons is typically measured by imaging K-alpha fluorescence from metal targets created by the transporting electrons. The modifications due to hot electron scattering are considered using the PIC code LSP where the electron source has been generated by simulating the LPI for a range of intensities and materials and are compared to results from Monte Carlo simulations. We report on the results of these simulations. [Preview Abstract] |
Thursday, November 17, 2011 11:42AM - 11:54AM |
TO6.00012: Experimental and LSP modeling study of pre-pulse effects on the laser-plasma interaction by using a 527 nm laser pulse G.E. Kemp, D.W. Schumacher, A. Link, R.R. Freeman, H. Friesen, H.F. Tiedje, Y.Y. Tsui, R. Fedosejevs, D.P. Higginson, F.N. Beg, M.H. Key, H.S. McLean, P. Patel, R.B. Stephens We describe a study motivated by the Fast Ignition approach to inertial confinement fusion of the generation in metal of hot electrons using intense laser pulses. Hot electrons are excited in an underdense plasma interface. This interaction involves relativistic effects and instabilities that can drastically alter the pulse and modify the ensuing laser-plasma interaction (LPI). In order to study the effect of this pre-plasma on the LPI and electron transport, slab and ``buried-cone'' targets were shot on Titan at the Jupiter Laser Facility using relatively clean 527 nm wavelength pulses with varying levels of injected pre-pulse energy. We compare the experimental results to simulations using the PIC code LSP. The simulations, in 2D3V Cartesian, are performed using full-scale targets and laser pulse. [Preview Abstract] |
Thursday, November 17, 2011 11:54AM - 12:06PM |
TO6.00013: LSP modeling of ultra-intense lasers on cone-coupled wire targets: effect of cone thickness Chris Orban, Vladimir Ovichinnikov, Kramer Akli, Anthony Link, Douglass Schumacher, Richard Freeman Experiments with ultra-intense laser pulses incident on cone-coupled wire targets can potentially yield valuable information on electron excitation and transport physics relevant to the fast ignition (FI) fusion regime. Using the PIC code LSP, we present fully kinetic simulations with fully consistent laser E \& B fields designed to model mm-scale cone-wire experiments conducted with the Titan laser at LLNL. We investigate and explain the strong experimental trend for thicker cones to produce a lower K$_\alpha$ yield. We find that the K$_\alpha$ signal does sensitively depend on the details of the hot electron transport, refluxing and interaction with the cone. Comparison to other recent works and implications for FI are also discussed. [Preview Abstract] |
Thursday, November 17, 2011 12:06PM - 12:18PM |
TO6.00014: LSP Simulations of High Intensity Short Pulse Lasers Incident On Reduced Mass Targets Frank W. King, Vladimir M. Ovchinnikov, Douglass Schumacher, Kramer U. Akli, Richard R. Freeman Reduced mass targets allow study of the surface heating and volumetric heating regimes which are important for a variety of applications. We present the results of fully kinetic 2D simulations, using the PIC code LSP, that model full scale laser pulses incident on full scale targets as a function of intensity, spot size, pre-plasma, and target lateral extent and thickness. The simulations run for as long as 20 ps in some cases. We observe complex target deformation including the formation of shocks that vary with lateral position and compare to recent experiment [1,2].\\[4pt] [1] K.U. Akli, et al, Phys. Rev. Lett. \textbf{100}, 165002 (2008).\\[0pt] [2] K.U. Akli, et al, APS DPP 2011. [Preview Abstract] |
Thursday, November 17, 2011 12:18PM - 12:30PM |
TO6.00015: LSP simulations of eliminating electron refluxing in Fast Ignition related experiments Vladimir Ovchinnikov, Kramer Akli, Gregory Kemp, Andrew Krygier, Linn Van Woerkom, Douglass Schumacher, Richard Freeman In previous work\footnote{V.M. Ovchinnikov et al, Phys. Plasmas, to be published in July, 2011} we found that refluxing from the front, back and side surfaces of a target gives rise to K$_{\alpha}$ images that are not necessarily representative of the FI-relevant, hot electrons. Placing a thick layer of low-Z material on the back of the target (called the Get-Lost-Layer or GLL) can reduce electron refluxing without strongly attenuating the K$_{\alpha }$ signal. We present the results of fully kinetic 2D simulations, using the PIC code LSP, of eliminating electron refluxing in buried cone targets for the perfect case when all electrons are stopped in the GLL. Our simulation results are in good agreement with recent experiments at Titan laser at LLNL in 2009, indicating that carbon GLLs successfully eliminate electron refluxing. This work was supported by the U.S. Department of Energy under contracts DE-FC02-04ER54789, DE-FG02-05ER54834, and allocations of computing time from the LLNL Institutional Computing Grand Challenge program. [Preview Abstract] |
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