Structure and Dynamics of Colliding Plasma Jets

C. K. Li, D. D. Ryutov, S. X. Hu, M. J. Rosenberg, A. B. Zylstra, F. H. Séguin, J. A. Frenje, D. T. Casey, M. Gatu Johnson, M. J.-E. Manuel, H. G. Rinderknecht, R. D. Petrasso, P. A. Amendt, H. S. Park, B. A. Remington, S. C. Wilks, R. Betti, D. H. Froula, J. P. Knauer, D. D. Meyerhofer, R. P. Drake, C. C. Kuranz, R. Young, and M. Koenig

Phys. Rev. Lett. 111, 235003 – Published 3 December 2013

Abstract

Monoenergetic-proton radiographs of laser-generated, high-Mach-number plasma jets colliding at various angles shed light on the structures and dynamics of these collisions. The observations compare favorably with results from 2D hydrodynamic simulations of multistream plasma jets, and also with results from an analytic treatment of electron flow and magnetic field advection. In collisions of two noncollinear jets, the observed flow structure is similar to the analytic model’s prediction of a characteristic feature with a narrow structure pointing in one direction and a much thicker one pointing in the opposite direction. Spontaneous magnetic fields, largely azimuthal around the colliding jets and generated by the well-known $\nabla T_{e} \times \nabla n_{e}$ Biermann battery effect near the periphery of the laser spots, are demonstrated to be “frozen in” the plasma (due to high magnetic Reynolds number ${Re}_{M} \sim 5 \times 10^{4}$ ) and advected along the jet streamlines of the electron flow. These studies provide novel insight into the interactions and dynamics of colliding plasma jets.

Received 24 August 2013

DOI:https://doi.org/10.1103/PhysRevLett.111.235003

Authors & Affiliations

C. K. Li^1,*, D. D. Ryutov², S. X. Hu³, M. J. Rosenberg¹, A. B. Zylstra¹, F. H. Séguin¹, J. A. Frenje¹, D. T. Casey^1,†, M. Gatu Johnson¹, M. J.-E. Manuel^1,‡, H. G. Rinderknecht¹, R. D. Petrasso¹, P. A. Amendt², H. S. Park², B. A. Remington², S. C. Wilks², R. Betti³, D. H. Froula³, J. P. Knauer³, D. D. Meyerhofer³, R. P. Drake⁴, C. C. Kuranz⁴, R. Young⁴, and M. Koenig⁵

¹Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
²Lawrence Livermore National Laboratory, Livermore, California 94550, USA
³Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623, USA
⁴University of Michigan, Ann Arbor, Michigan 48109, USA
⁵Laboratoire pour l’Utilisation des Lasers Intenses, UMR 7605, CNRS-CEA-Université Paris VI-Ecole Polytechnique, 91128 Palaiseau Cedex, France

^*Corresponding author. ckli@mit.edu
^†Present address: Lawrence Livermore National Laboratory, Livermore, CA 94550, USA.
^‡Present address: University of Michigan, Ann Arbor, MI 48109, USA.

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Vol. 111, Iss. 23 — 6 December 2013

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Images

Figure 1
Schematic diagram of the experimental setup. The proton backlighter (imploded $D {}^{3}{He}$ -filled thin-glass-shell capsule driven by 30-OMEGA laser beams) is typically 1 cm from the collision region and has the illustrated monoenergetic spectra from the reactions $D + {}^{3}{He} \to α + p$ (14.7 MeV) and $D + D \to T + p$ (3.0 MeV). The typical backlighter spatial and temporal resolutions are $\sim 40 μ m$ and $\sim 80 ps$ , respectively [43]. Sample images of proton fluence, taken with 15-MeV $D {}^{3}{He}$ protons at $\sim 4 ns$ from the onset of the laser drive on the $V$ -shaped targets at different angles, are shown. The dashed-dotted lines shown in the images indicate the bisector planes for various cases. The dashed square indicates the field of view of the C39 proton detector, but shown as if it were rotated 90° into the plane of the diagram. The distance from the sample region to the detector is 27 cm.Reuse & Permissions
Figure 2
Lineouts from images taken at $\sim 4.7 ns$ with 15 and 3.3 MeV protons from head-on collisions of two plasma jets are shown. The solid and dashed profiles correspond to the solid and dashed straight lines in the images, indicating the different energies of the backlighting protons. The ratio of the widths of the flattened region demonstrates the dominant role of magnetic field in forming such a structure.Reuse & Permissions
Figure 3
2D DRACO hydrodynamic simulations of the two head-on plasma jets which displays the jets’ formation at $t \approx 1.4 ns$ ; propagation at $t \approx 2.2 ns$ (a clear bow shock structure is seen in front of the jets); the onset of plasma flow in the transverse direction, and the formation of a high-pressure region in the bisector plane, at $t \approx 2.6 ns$ ; and the transverse expansion of the high-pressure region in the bisector plane $t \approx 4.1 ns$ . In this simulation, a low density ( $\sim 2 \times 10^{- 6} g {cm}^{- 3}$ ) deuterium gas has been added to the background. The simulation of plasma flow (4.1 ns) appears to be quite consistent with the shape of the proton deflection images shown in Figs. 1, 2.Reuse & Permissions
Figure 4
Proton image (a), numerical simulation (b), and analytical model (c) of streamlines of electron “effective flow” for collisions of two counterstreaming plasma jets (head-on).Reuse & Permissions
Figure 5
Schematic drawing of coordinate system (a) to illustrate the collisions of two plasma jets at an $angle = 180 ° - 2 α$ . Proton images of the collisions of two identical plasma jets (white arrows) is compared with model predicted streamlines of effective electron flow at 90° ( $α = 45 °$ ) in (b) and 135° ( $α = 22.5 °$ ) in (c), respectively. The dashed-dotted lines shown in the images indicate the bisector planes.Reuse & Permissions

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