Blanc SIMI 4 - Blanc - SIMI 4 - Physique des milieux condensés et dilués

Laser plasma interaction in realistic hydrodynamic and geometry – ILPHYGERIE

Submission summary

In all laser-fusion schemes, laser-plasma interaction (LPI) has to be thoroughly controlled to allow an efficient transfer of the laser energy to the target. The main mechanisms involved in LPI affect the quality of the transmitted laser energy and the quantity of the absorbed laser energy. The latter could be significantly reduced because of the backscattering instabilities. The backscattering processes include the Stimulated Brillouin Scattering (SBS), and the Stimulated Raman Scattering (SRS). Laser-plasma interaction has been studied theoretically, numerically and experimentally for decades. However, it is only during the last ten years that the experimental methods for controlling these parametric instabilities have been developed (Labaune /et al./, 2004 and 2007, Depierreux /et al./, 2011). New numerical tools are now clearly needed to describe the parametric instabilities involving electron plasma waves such as SRS and the two plasmon decay (TPD). On the other hand, the recent National Ignition Facility (NIF) experiments have evidenced not only large levels of Stimulated Raman backscattering but also a significant energy transfer between the cones together with a strongly reduced laser energy absorption. The propagation of the laser beams over a few millimetres in inhomogeneous plasma, together with their mutual interaction in the spatial domain where they cross each other, have therefore been identified as crucial bottlenecks in the current NIF ignition experiments (Lindl /et al./, 2011, Igumenshchev /et al./, 2010). An additional numerical effort is consequently necessary in order to become able to describe multi-beam interaction in the complex geometries encountered in megajoule scale hohlraums and in direct drive implosion schemes.

It is in this context that we had organized, several years ago, a consortium coordinating leading French scientists from the CEA and academic laboratories in the domain of laser-plasma interaction physics. It received a support from the ANR within the project CORPARIN (2008-2011). The latter allowed an operational coordination between the laboratories in terms of regular workshops, diagnostic tools and a series of experimental campaigns on the largest French laser installations (LULI and LIL, Labaune /et al./, 2010, Depierreux /et al./, 2011). These experiments were then interpreted jointly by the theoretical groups, each of them possessing complementary numerical tools. This collaboration resulted in the validation of predictive models of laser beam plasma smoothing, SBS and filamentation (Grech /et al./, 2009).

Although our present ILPHyGerieproposal covers issues different from those pursued in the CORPARIN project, it is its natural continuation: indeed, it is similarly aimed at grouping together most of the existing French skills in order to develop new theoretical models and numerical tools to simulate and predict SRS and crossing beam effects in fusion plasmas. These developments will be coordinated with dedicated experiments performed in conditions relevant to fusion, namely mm spatial scales together with several keV plasma temperatures. Such experiments are possible only on kilo-Joule installations --LULI, LIL and Omega, the latter being the only one providing the convergent geometry. Our project contains important code developments and theoretical modelling going from PIC codes describing sub-mm wave-particle interaction in the context of SRS, to fluid codes in which SRS will be modelled at the mm scale. Regarding the beam crossing effects, the first step will consist in describing multiple beam crossing within the paraxial approximation. The validity of this description could then be checked by comparison with the results obtained with the non-paraxial code presently available within our consortium.

Our project is ambitious. The success of the previous ANR project conducted by the same groups represents a guarantee for its success.

Project coordination

Sylvie DEPIERREUX (Commissariat à l'énergie atomique et aux énergies alternatives) – sylvie.depierreux@polytechnique.edu

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

CEA Commissariat à l'énergie atomique et aux énergies alternatives
CPHT Centre de Physique Théorique
LULI Laboratoire pour l'Utilisation des laser intenses
CELIA Centre des Laser Intenses et Apllications

Help of the ANR 385,980 euros
Beginning and duration of the scientific project: October 2012 - 36 Months

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