Browsing by Author "Ryutov, D.D."

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    Development of an interpretive simulation tool for the proton radiography technique
    (AIP Publishing LLC., 2015) Levy, M.C.; Ryutov, D.D.; Wilks, S.C.; Ross, J.S.; Huntington, C.M.; Fiuza, F.; Martinez, D.A.; Kugland, N.L.; Baring, M.G.; Park, H.-S.
    Proton radiography is a useful diagnostic of high energy density (HED) plasmas under active theoretical and experimental development. In this paper, we describe a new simulation tool that interacts realistic laser-driven point-like proton sources with three dimensional electromagnetic fields of arbitrary strength and structure and synthesizes the associated high resolution protonradiograph. The present tool’s numerical approach captures all relevant physics effects, including effects related to the formation of caustics. Electromagnetic fields can be imported from particle-in-cell or hydrodynamic codes in a streamlined fashion, and a library of electromagnetic field “primitives” is also provided. This latter capability allows users to add a primitive, modify the field strength, rotate a primitive, and so on, while quickly generating a high resolution radiograph at each step. In this way, our tool enables the user to deconstruct features in a radiograph and interpret them in connection to specific underlying electromagnetic field elements. We show an example application of the tool in connection to experimental observations of the Weibel instability in counterstreaming plasmas, using ∼108 particles generated from a realistic laser-driven point-like proton source, imaging fields which cover volumes of ∼10 mm3. Insights derived from this application show that the tool can support understanding of HED plasmas.
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    Scaled laboratory experiments explain the kink behaviour of the Crab Nebula jet
    (Springer Nature, 2016) Li, C.K.; Tzeferacos, P.; Lamb, D.; Gregori, G.; Norreys, P.A.; Rosenberg, M.J.; Follett, R.K.; Froula, D.H.; Koenig, M.; Seguin, F.H.; Frenje, J.A.; Rinderknecht, H.G.; Sio, H.; Zylstra, A.B.; Petrasso, R.D.; Amendt, P.A.; Park, H.S.; Remington, B.A.; Ryutov, D.D.; Wilks, S.C.; Betti, R.; Frank, A.; Hu, S.X.; Sangster, T.C.; Hartigan, P.; Drake, R.P.; Kuranz, C.C.; Lebedev, S.V.; Woolsey, N.C.
    The remarkable discovery by the Chandra X-ray observatory that the Crab nebulaﾒs jet periodically changes direction provides a challenge to our understanding of astrophysical jet dynamics. It has been suggested that this phenomenon may be the consequence of magnetic fields and magnetohydrodynamic instabilities, but experimental demonstration in a controlled laboratory environment has remained elusive. Here we report experiments that use high-power lasers to create a plasma jet that can be directly compared with the Crab jet through well-defined physical scaling laws. The jet generates its own embedded toroidal magnetic fields; as it moves, plasma instabilities result in multiple deflections of the propagation direction, mimicking the kink behaviour of the Crab jet. The experiment is modelled with three-dimensional numerical simulations that show exactly how the instability develops and results in changes of direction of the jet.