arXiv subjects

Denis Pesme

Publications and source records attributed to Denis Pesme.

2 recordsLinked to original sources

arXiv2016

Ponderomotive laser channelling and multi-channelling in homogeneous underdense plasma

We have studied laser pulse channeling in underdense plasma by means of analytical theory and 3D PIC simulations. The most significant result of this paper is the demonstration of the single fully evacuated stationary channel solution can be reached an asymptotic state in PIC simulations. In the lower density and for a laser power above channeling power, we were able to reproduce in PIC simulations the analytical curve. We showed that single channels are stable structures against symmetric perturbations. We also studied the formation of the ring structure in theory and simulations. An evacuated ring enclosed by an electron filament was observed in our 3D simulations. However they always coexist with the main laser mode. The threshold power for ring structure formation is found. Our studies on stability of the rings against asymmetric perturbations show that ring structure is not stable against azimuthal perturbations. The growth rate of the instability is shorter for higher densities and it is therefore more effective at higher densities.

physics.plasm-ph↗

arXiv2003

Harmonic decomposition to describe the nonlinear evolution of Stimulated Brillouin Scattering

An efficient method to describe the nonlinear evolution of Stimulated Brillouin Scattering in long scale-length plasmas is presented. The method is based on a decomposition of the hydrodynamics variables in long- and short-wavelength components. It makes it possible to describe the self-consistent coupling between the plasma hydrodynamics, Stimulated Brillouin Scattering, and the generation of harmonics of the excited ion acoustic wave (IAW). This description is benchmarked numerically and proves to be reliable even in the case of an undamped ion acoustic wave. The momentum transferred from the electromagnetic waves to the plasma ions is found to induce a plasma flow which modifies the resonant three wave coupling between the IAW and the light waves. A novel picture of SBS arises, in which both IAW harmonics and flow modification reduce the coherence of SBS by inducing local defects in the density and velocity profiles. The spatial domains of Stimulated Brillouin activity are separated by these defects and are consequently uncorrelated, resulting in a broad and structured spectrum of the scattered light and in a temporally chaotic reflectivity.

physics.plasm-ph↗