Enhancement of Quasistationary Shocks and Heating via Temporal Staging in a Magnetized Laser-Plasma Jet

D. P. Higginson, B. Khiar, G. Revet, J. Béard, M. Blecher, M. Borghesi, K. Burdonov, S. N. Chen, E. Filippov, D. Khaghani, K. Naughton, H. Pépin, S. Pikuz, O. Portugall, C. Riconda, R. Riquier, R. Rodriguez, S. N. Ryazantsev, I. Yu. Skobelev, A. Soloviev, M. Starodubtsev, T. Vinci, O. Willi, A. Ciardi, and J. Fuchs

Phys. Rev. Lett. 119, 255002 – Published 22 December 2017

Abstract

We investigate the formation of a laser-produced magnetized jet under conditions of a varying mass ejection rate and a varying divergence of the ejected plasma flow. This is done by irradiating a solid target placed in a 20 T magnetic field with, first, a collinear precursor laser pulse ( $1 0^{12} W / {cm}^{2}$ ) and, then, a main pulse ( $1 0^{13} W / {cm}^{2}$ ) arriving 9–19 ns later. Varying the time delay between the two pulses is found to control the divergence of the expanding plasma, which is shown to increase the strength of and heating in the conical shock that is responsible for jet collimation. These results show that plasma collimation due to shocks against a strong magnetic field can lead to stable, astrophysically relevant jets that are sustained over time scales 100 times the laser pulse duration (i.e., $> 70 ns$ ), even in the case of strong variability at the source.

Received 3 June 2017

DOI:https://doi.org/10.1103/PhysRevLett.119.255002

Physics Subject Headings (PhySH)

Inertial confinement fusion Laboratory studies of space & astrophysical plasmas Laser-plasma interactions Magnetohydrodynamics Magnetoinertial fusion Space & astrophysical plasma

Astrophysical jets Magnetized plasma

Plasma Physics

Authors & Affiliations

D. P. Higginson^1,2,*, B. Khiar^3,4, G. Revet^1,5, J. Béard⁶, M. Blecher⁷, M. Borghesi⁸, K. Burdonov⁵, S. N. Chen^1,5, E. Filippov^9,10, D. Khaghani¹¹, K. Naughton⁸, H. Pépin¹², S. Pikuz^9,10, O. Portugall⁶, C. Riconda¹³, R. Riquier^1,14, R. Rodriguez¹⁵, S. N. Ryazantsev^9,16, I. Yu. Skobelev^9,10, A. Soloviev⁵, M. Starodubtsev⁵, T. Vinci¹, O. Willi⁷, A. Ciardi^3,4, and J. Fuchs^1,5

¹Laboratoire pour l’Utilisation des Lasers Intenses–CNRS, CEA, École Polytechnique, Univ. Paris-Saclay, Sorbonne Univ., UPMC Univ. Paris 06, F-91128 Palaiseau cedex, France
²Lawrence Livermore National Laboratory, Livermore, California 94551, USA
³Sorbonne Univ., UPMC Univ. Paris 6, UMR 8112, LERMA, F-75005 Paris, France
⁴LERMA, Observatoire de Paris, PSL Research University, CNRS, UMR 8112, F-75014 Paris, France
⁵Institute of Applied Physics, 46 Ulyanov Street, 603950 Nizhny Novgorod, Russia
⁶LNCMI, UPR 3228, CNRS-UGA-UPS-INSA, 31400 Toulouse, France
⁷Institut für Laser- und Plasmaphysik, Heinrich-Heine-Universität Düsseldorf, D-40225 Düsseldorf, Germany
⁸Centre for Plasma Physics, Queen’s University Belfast, Belfast BT7 1NN, United Kingdom
⁹Joint Institute for High Temperatures, RAS, 125412 Moscow, Russia
¹⁰National Research Nuclear University “MEPhI,” 115409 Moscow, Russia
¹¹GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt, Germany
¹²INRS-ÉMT, 1650 bd. L. Boulet, J3X1S2 Varennes, Québec, Canada
¹³LULI, Sorbonne Univ.–UPMC Univ. Paris 06, École Polytechnique, CNRS, CEA, 75005 Paris, France
¹⁴CEA, DAM, DIF, 91297 Arpajon, France
¹⁵Departamento de Fisica de la Universidad de Las Palmas de Gran Canaria, E-35017 Las Palmas de Gran Canaria, Spain
¹⁶M.V. Lomonosov Moscow State University, 119991 Moscow, Russia

^*higginson2@llnl.gov

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Vol. 119, Iss. 25 — 22 December 2017

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Images

Figure 1
Schematic of the experimental setup and 3D MHD simulations of the overall plasma dynamics. The volume rendering shows the simulated mass density at 22 ns, for the case of a single 17 J pulse, with $1 / 4$ of the volume removed to show the internal flow structure. Two collinear laser pulses (3 and $17 J$ ), that are temporally offset by either 9 or 19 ns, irradiate a $(C_{2} F_{4})_{n}$ target embedded in a 20 T magnetic field. The diagnostic observation axis is also shown.
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Figure 2
Plasma electron density measured via interferometry, and analyzed using Abel inversion [29, 30], in pseudocolor with identical color scales as shown on the right. The central pixels are removed due to the uncertainty of the Abel inversion on axis. Notice that the images appear very symmetric. The three columns show times of 10 (a–c), 42 (d–f), and 70 ns (g–i) measured from the beginning of the main pulse irradiation. The top row (a,d,g) shows the case of main pulse alone, the middle (b,e,h) and bottom (c,f,i) rows show the temporally staged cases of 9 and 19 ns delay, respectively.
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Figure 3
X-ray spectrometry measurements of $T_{e}$ from the FSSR. Lines with circles ( $\times ’ s$ ) represent the main-pulse-only setup with (without) an applied 20 T $B$ field. Lines with diamonds and squares show cases with a precursor of 9 and 19 ns delay, respectively.
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Figure 4
Streaked optical emission profiles along the center of the plasma expansion axis (smoothed with a 5-pixel Gaussian) plotted with the same linear color scale for (a) the main-pulse-only case and (b) [(c)] the precursor and main pulses with a 9 ns [19 ns] delay between them. Time is measured from the beginning of the main pulse. Note the small signal from the precursor interaction in (b) [(c)] at $- 9 ns$ [ $- 19 ns$ ]. The profiles in (a) and (b) were taken over successive shots and with the exact same detector settings. Profile (c) was taken at a later time and thus was slightly scaled and shifted for comparison with the previous profiles. The thin streak in (c) at $t = - 15 ns$ , $z = 2.25 mm$ is from the interferometry probe.
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Figure 5
3D MHD simulations results. (a)–(c) Pseudocolor maps of $n_{e}$ in the two-pulse configuration with a 19 ns delay. Times are measured from the main-pulse arrival. Arrows represent fluid velocity (not scaled in magnitude) and magnetic field lines are shown. Panel (a) shows the plasma created by the low energy precursor at a time just before the arrival of the main pulse. The white dashed line corresponds to the isocontour at $0.1 n_{c}$ . (d) Profiles of $n_{e}$ , averaged over the laser focal spot, for a case of precursor-only irradiation at 9, 19, and 39 ns after precursor irradiation. Cases with (solid line) and without (dashed line) magnetic field are shown. (e) Ratio of longitudinal ( $K_{z} = 0.5 ρ v_{z}^{2}$ ) to radial [ $K_{x y} = 0.5 ρ (v_{x}^{2} + v_{y}^{2})$ ] kinetic energy integrated over the entire plasma volume, for the main-pulse-only (M) and the temporally staged cases ( $P + M$ ).
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