Thomson-Scattering Study of the Subharmonic Decay of Ion-Acoustic Waves Driven by the Brillouin Instability

Bandulet, H.; Labaune, C.; Lewis, K. W.; Depierreux, S.

doi:10.1103/physrevlett.93.035002

Cited by 48 publications

(20 citation statements)

References 15 publications

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“…These simulations results and those reported in Refs. 1 and 2 support recent experimental observations of the importance of ion trapping effects 19,20 and the two-ion-wave decay 21,22 associated with SBS.…”

Section: Introductionsupporting

confidence: 74%

Effects of ion-ion collisions and inhomogeneity in two-dimensional kinetic ion simulations of stimulated Brillouin backscattering

et al. 2006

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Langdon, and E.A. Williams, Phys. Plasmas 4, 956 (1997)] hybrid code (kinetic particle ions and Boltzmann fluid electrons) have been used to investigate the saturation of stimulated Brillouin backscatter (SBBS) instability including the effects of ion-ion collisions and inhomogeneity. Ion-ion collisions tend to increase ion-wave dissipation, which decreases the gain exponent for stimulated Brillouin backscattering; and the peak Brillouin backscatter reflectivities tend to decrease with increasing collisionality in the simulations. Two types of Langevin-operator, ion-ion collision models were implemented in the simulations. In both models used the collisions are functions of the local ion temperature and density, but the collisions have no velocity dependence in the first model. In the second model, the collisions are also functions of the energy of the ion that is being scattered so as to represent a Fokker-Planck collision operator. Collisions decorrelate the ions from the acoustic waves in SBS, which disrupts ion trapping in the acoustic wave. Nevertheless, ion trapping leading to a hot ion tail and two-dimensional physics that allows the SBS ion waves to nonlinearly scatter remain robust saturation mechanisms for SBBS in a high-gain limit over a range of ion collisionality. SBS 2 backscatter in the presence of a spatially nonuniform plasma flow is also investigated.Simulations show that depending on the sign of the spatial gradient of the flow relative to the backscatter, ion trapping effects that produce a nonlinear frequency shift can enhance (auto-resonance) or decrease (anti-auto-resonance) reflectivities in agreement with theoretical arguments. PACS: 52.38.-r 52.65.Rr 3

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Section: Introductionsupporting

confidence: 74%

Effects of ion-ion collisions and inhomogeneity in two-dimensional kinetic ion simulations of stimulated Brillouin backscattering

et al. 2006

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“…Concerning SBS, our 3D numerical simulation results and our modeling are both in a good qualitative agreement with the experimental observations concerning its localization in the density profile and its reflectivity. In the regime of high laser intensity, they all show a weak dependence of the time averaged reflectivity on the laser intensity; the average level hRi SBS of the SBS reflectivity R SBS (averaged over the period of time during which R SBS is not negligible) is in the order of 10%, 28 and it depends only weakly on the laser intensity. As the temporal window during which the reflectivity is non-negligible is short (of the order of 100 ps) compared to the laser pulse temporal length (of the order of 1 ns), the overall time averaged reflectivity is very small, in the order of a few per cents at most.…”

Section: Discussionmentioning

confidence: 99%

“…The physical plasma parameters (density profile, temperatures, effective charge, and atomic number) of these simulations correspond to experiments carried out with a single laser speckle at the Laboratoire pour l'Utilisation des Lasers Intenses (LULI), 27,28,40 for which the plasma and laser conditions were carefully characterized. We assumed that the ion acoustic waves are strongly damped so that SBS develops in the convective regime of strongly damped IAW; we also assumed that the IAW damping could be described by the simple ad-hoc damping rate iaw ¼ 0:17 x iaw , x iaw denoting the IAW frequency.…”

Section: Characterization Of the Laser Pulse And Of The Plasma Comentioning

confidence: 99%

“…Past this temporal domain, R SBS decreases as soon as the laser amplitude starts decreasing, and it remains at the level of very small values, consistently with the LULI experimental observations. 28 We now compute the Rosenbluth amplification gain factor 1,2,4,44 corresponding to what would be the spatial growth of SBS if self-focusing was not playing a significant role; this limit corresponds to the initial times of the simulations, when self-focusing has not yet time to take place. In this limit, the SBS growth is simply limited by the inhomogeneity of the expansion velocity.…”

Section: A Parameters Of the Reference Simulationsmentioning

confidence: 99%

“…[24][25][26][27][28][29][30] Several of these experiments have been dedicated to the study of self-focusing 24 and of SBS [25][26][27][28][29][30] in a well defined inhomogeneous plasma. In this context, well diagnosed experiments represent a fundamental platform for comparing the experimental results with their numerical modeling.…”

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confidence: 99%

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Stimulated Brillouin scattering reduction induced by self-focusing for a single laser speckle interacting with an expanding plasma

Masson-Laborde¹,

Hüller²,

Pesme³

et al. 2014

Physics of Plasmas

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Relativistic self-focusing and its effect on stimulated Raman and stimulated Brillouin scattering in laser plasma interaction Phys. Plasmas 8, 3419 (2001); 10.1063/1.1377048 Stimulated Brillouin and Raman scattering from a randomized laser beam in large inhomogeneous collisional plasmas. II. Model description and comparison with experiments Phys. Plasmas 8, 1636 (2001); 10.1063/1.1357218 Effect of pump depletion and self-focusing on stimulated Brillouin scattering process in laser-plasma interactions Phys. Plasmas 6, 927 (1999); 10.1063/1.873332Effect of the speckle self-focusing on the stationary stimulated Brillouin scattering reflectivity from a randomized laser beam in an inhomogeneous plasma The origin of the low level of stimulated Brillouin scattering (SBS) observed in laser-plasma experiments carried out with a single laser speckle is investigated by means of three-dimensional simulations and modeling in the limit when the laser beam power P is well above the critical power for ponderomotive self-focusing We find that the order of magnitude of the time averaged reflectivities, together with the temporal and spatial SBS localization observed in our simulations, are correctly reproduced by our modeling. It is observed that, after a short transient stage, SBS reaches a significant level only (i) as long as the incident laser pulse is increasing in amplitude and (ii) in a single self-focused speckle located in the low-density front part of the plasma. In order to describe self-focusing in an inhomogeneous expanding plasma, we have derived a new Lagrangian density describing this process. Using then a variational approach, our model reproduces the position and the peak intensity of the self-focusing hot spot in the front part of the plasma density profile as well as the local density depletion in this hot spot. The knowledge of these parameters then makes it possible to estimate the spatial amplification of SBS as a function of the laser beam power and consequently to explain the experimentally observed SBS reflectivity, considerably reduced with respect to standard theory in the regime of large laser beam power. V C 2014 AIP Publishing LLC.

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Saturation of Laser–Plasma Instabilities and Other Nonlinear Effects

Michel

2023

Graduate Texts in Physics

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Thomson-Scattering Study of the Subharmonic Decay of Ion-Acoustic Waves Driven by the Brillouin Instability

Cited by 48 publications

References 15 publications

Effects of ion-ion collisions and inhomogeneity in two-dimensional kinetic ion simulations of stimulated Brillouin backscattering

Effects of ion-ion collisions and inhomogeneity in two-dimensional kinetic ion simulations of stimulated Brillouin backscattering

Stimulated Brillouin scattering reduction induced by self-focusing for a single laser speckle interacting with an expanding plasma

Saturation of Laser–Plasma Instabilities and Other Nonlinear Effects

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