Showing papers by "Lin Yin published in 2019"
TL;DR: In this article, the nonlinear saturation of crossed-beam energy transfer (CBET) for multispeckled laser beams crossing at arbitrary angles is examined using vector particle-in-cell simulations.
Abstract: The nonlinear saturation of crossed-beam energy transfer (CBET) for multispeckled laser beams crossing at arbitrary angles is examined using vector particle-in-cell simulations. CBET is found to saturate on fast (∼10s of picosecond) time scales involving ion trapping and excitation of oblique forward stimulated Raman scattering (FSRS). Ion trapping reduces wave damping and speckle interaction increases wave coherence length, together enhancing energy transfer; ion acoustic wave (IAW) breakup in the direction transverse to the wavenumber increases wave damping and contributes to CBET saturation. The seed beam can become unstable to oblique FSRS, which leads to beam deflection at a large angle and a frequency downshift (by the plasma frequency). FSRS saturates on fast ∼picosecond time scales by electron plasma wave self-focusing, leading to enhanced side-loss hot electrons with energy exceeding 300 keV. This may contribute to fuel preheat but FSRS can be mitigated by the presence of a density gradient. Such growth of FSRS contributes to the saturation of CBET. Scaling simulations show that CBET, as well as FSRS and hot electrons, increases with beam average intensity, beam diameter, and crossing area, but that CBET is limited by the excitation of FSRS and IAW breakups in addition to pump depletion. FSRS deflects the seed beam energy by greater than 40% of the incident beam energy and puts a few percent of the incident beam energy into hot electrons. FSRS limits the efficacy of CBET for symmetry tuning at late stages in the implosion and may account for a large portion of the “missing energy” in implosions that use gas-filled hohlraums.
29 citations
TL;DR: In this article, the applicability of the 1D ambipolarity condition is evaluated in 2D and 3D simulations of a plasma interface with a sinusoidal perturbation.
Abstract: The physics of mixing in plasmas is of fundamental importance to inertial confinement fusion and high energy density laboratory experiments. Two- and three-dimensional (2D and 3D) particle-in-cell simulations with a binary collision model are used to explore kinetic effects arising during the mixing of plasma media. The applicability of the one-dimensional (1D) ambipolarity condition is evaluated in 2D and 3D simulations of a plasma interface with a sinusoidal perturbation. The 1D ambipolarity condition is found to remain valid in 2D and 3D, as electrons and ions flow together required for J = 0. Simulations of perturbed interfaces show that diffusion-induced total pressure imbalance and hydroflows flatten fine interface structures and drive rapid atomic mix. The atomic mix rate from a structured interface is faster than the ∼ t scaling obtained from 1D theory in the small-Knudsen-number limit. Plasma kinetic effects inhibit the growth of the Rayleigh-Taylor instability at small wavelengths and result in a nonmonotonic growth rate scaling with wavenumber k with a maximum at a low k value, much different from Agk (where A is the Atwood number and g is the gravitational constant) as expected in the absence of plasma kinetic effects. Simulations under plasma conditions relevant to MARBLE separated-reactant experiments on Omega and the NIF show kinetic modification of DT fusion reaction rates. With non-Maxwellian distributions and relative drifts between D and T ions, DT reactivity is higher than that inferred from rates using stationary Maxwellian distributions. Reactivity is also found to be reduced in the presence of finite-Knudsen-layer losses.
21 citations
TL;DR: In this paper, the authors show how the higher charge-to-mass ratio of the protons results in species stratification and late-time suppression of the carbon acceleration, and propose an alternative shaping of the rear surface of 7LiD to increase the number of high-energy deuterons in the beam.
Abstract: Particle-in-cell simulations of laser- ion acceleration demonstrate marked discrepancies in the acceleration experienced by the different ion species in complex target compositions, especially when the target becomes relativistically transparent to the pulse during irradiation. Beginning with proton contaminants in a carbon target, we show how the higher charge-to-mass ratio of the protons results in species stratification and late-time suppression of the carbon acceleration. The target normal sheath acceleration (TNSA) primarily experienced by the protons can be exploited to mitigate this tamping by using a shaped rear surface of the target, leaving the break-out afterburner-driven carbons to accelerate close to the laser axis and then experience less tamping during a late-time TNSA phase. We then explore preferentially accelerating the lighter species in a mixed composition target, particularly focusing on deuteron beam applications. We examine three different target compositions with the same areal electron density, CD2, CH2, and 7LiD, and propose an alternative shaping of the rear surface of 7LiD to increase the number of high-energy deuterons in the beam.
4 citations
Posted Content•
University of Rochester1, Lawrence Livermore National Laboratory2, Los Alamos National Laboratory3, University of Maryland, College Park4, University of California, San Diego5, United States Naval Research Laboratory6, Ohio State University7, University of Bordeaux8, Lawrence Berkeley National Laboratory9, Stanford University10, Princeton University11, University of Texas at Austin12, University of Michigan13, University of California, Los Angeles14, University of Alberta15, University of Central Florida16, Colorado State University17, University of Lisbon18, University of Nebraska–Lincoln19
TL;DR: An overview from the past and an outlook for the future of fundamental laser-plasma interactions research enabled by emerging laser systems are presented.
Abstract: Author(s): Palastro, JP; Albert, F; Albright, B; Jr, TM Antonsen; Arefiev, A; Bates, J; Berger, R; Bromage, J; Campbell, M; Chapman, T; Chowdhury, E; Colaitis, A; Dorrer, C; Esarey, E; Fiuza, F; Fisch, N; Follett, R; Froula, D; Glenzer, S; Gordon, D; Haberberger, D; Hegelich, BM; Jones, T; Kaganovich, D; Krushelnick, K; Michel, P; Milchberg, H; Moloney, J; Mori, W; Myatt, J; Nilson, P; Obenschain, S; Peebles, J; Penano, J; Richardson, M; Rinderknecht, H; Rocca, J; Schmitt, A; Schroeder, C; Shaw, J; Silva, L; Strozzi, D; Suckewer, S; Thomas, A; Tsung, F; Turnbull, D; Umstadter, D; Vieira, J; Weaver, J; Wei, M; Wilks, S; Willingale, L; Yin, L; Zuegel, J | Abstract: An overview from the past and an outlook for the future of fundamental laser-plasma interactions research enabled by emerging laser systems.
2 citations