Experimental Evidence of the Collective Brillouin Scattering of Multiple Laser Beams Sharing Acoustic Waves

C. Neuville, V. Tassin, D. Pesme, M.-C. Monteil, P.-E. Masson-Laborde, C. Baccou, P. Fremerye, F. Philippe, P. Seytor, D. Teychenné, W. Seka, J. Katz, R. Bahr, and S. Depierreux

Phys. Rev. Lett. 116, 235002 – Published 8 June 2016

Abstract

The indirect-drive scheme to inertial confinement fusion uses a large number of laser beams arranged in a symmetric angular distribution. Collective laser plasma instabilities can therefore develop that couple all the incident laser waves located in a cone to the daughter wave growing along the cone symmetry axis [D. F. DuBois et al., Phys. Fluids B 4, 241 (1992)]. With complementary diagnostics of Thomson scattering and of the scattered light, we demonstrate the occurrence of collective stimulated Brillouin sidescattering driving collective acoustic waves in indirect-drive experiments.

Received 20 October 2015

DOI:https://doi.org/10.1103/PhysRevLett.116.235002

Physics Subject Headings (PhySH)

Ion-acoustic waves Plasma waves Stimulated Brillouin & Raman scattering in plasmas

Plasma Physics

Authors & Affiliations

C. Neuville¹, V. Tassin¹, D. Pesme², M.-C. Monteil¹, P.-E. Masson-Laborde¹, C. Baccou³, P. Fremerye¹, F. Philippe¹, P. Seytor¹, D. Teychenné¹, W. Seka⁴, J. Katz⁴, R. Bahr⁴, and S. Depierreux¹

¹CEA, DAM, DIF, F-91297 Arpajon, France
²Centre de Physique Théorique, UMR 7644, CNRS-Ecole Polytechnique, 91128 Palaiseau cedex, France
³LULI, UMR 7605 CNRS-Ecole Polytechnique-CEA-Université Paris VI, 91128 Palaiseau cedex, France
⁴Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623-1299, USA

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Issue

Vol. 116, Iss. 23 — 10 June 2016

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Images

Figure 1
(a) Representation of the LEH showing the three cones of heater beams and the geometry of the TS diagnostic. (b) Schematic view of the 15 interaction beams around the Hohlraum axis. The directions of the IAWs driven by the laser beams of four representative cones are drawn. IAWa is the IAW excited along the Hohlraum axis by the ten beams of the 59° cone, IAWb is excited by beams 13, 66, 27, 32, 25, and 57, IAWc is excited by beams 12, 23, 57, and 62, and IAWd is along the axis of the cone formed by beams 47, 53, 57, and 59. (c) Directions of IAWc (in blue) such that it is amplified by the same SBS geometry for the four surrounding beams and angular distribution (in red) of the Thomson scattered light calculated for an electronic density of $0.1 n_{c}$ ( $n_{c}$ is the critical density for the 351-nm beams). (d) Thomson scattering geometry for probing the common ion acoustic wave (IAW1) driven along the axis of a 42° cone of 351-nm interaction beams with a 263-nm probe.
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Figure 2
Expansion velocity ( $u$ ) and acoustic velocity ( $c_{s}$ ) measured (a) in the spatial domain of beam crossing and (b) at $300 μ m$ outside the Hohlraum.
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Figure 3
(a) Time-resolved spectrum of the Thomson scattered light collected in the region of beam crossing. The pulse shapes of the probe beam and of the heater beams are shown in grey. (b) Time-resolved intensity of the light scattered off the IAW1, normalized to the intensity of the light scattered off the counterpropagating ion wave IAW2.
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Figure 4
(a) Time-resolved spectrum of the scattered light collected in the backward direction of beam 25. The solid grey line shows the wavelength calculated for the SBS of beam 13 in the collective instability that drives IAWb that is collected in the direction of FABS25. The two dashed lines represent the expected wavelength range for this scattered light, taking into account the aperture of the diagnostic and laser beams and the size of the crossing-beam volume. (b) Time-resolved spectrum of the scattered light collected in the backward direction of beam 30. As in (a), the grey lines represent the wavelength range calculated for the light scattered by beam 66 in the FABS30 direction off the collective IAWs driven along the Hohlraum axis by the ten-beam instability. (c) Scattered light wavelength for the signal measured in FABS30 at $t = 2.25 \pm 0.05 ns$ . (d) The directions of the IAWs having equal wave vectors are shown with respect to the ten laser beams of the 59° cone that stimulate IAWa. A collective ion acoustic wave is driven in each of the directions where multiple beams contribute. In the direction indicated as IAWa, the ten beams amplify the corresponding IAW. The regions shown in red represent the directions of scattering of beam 66 off IAWa.
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