The influence of stimulated Brillouin scattering on stimulated Raman scattering in inhomogeneous density plasma

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Abstract
A numerical investigation of the interplay of the two parametric scattering processes is reported. A 11/2 D particle-in-cell code has been used to simulate the laser irradiation of a plasma with a linear density profile. Fixed ion and mobile ion simulations have been carried out. In the latter, ion temperature allowed the onset of Brillouin scattering. Two types of density profile have been used: the first one centered on quart-critical density allows one to observe absolute Raman scattering; the second one with an uppermost density below quart-critical density has isolated convective Raman scattering. Absorption and scatter rates are presented for both profiles. Fast electron temperatures are also reported. Raman scattering is reduced by Brillouin scattering presence for both profiles, except in particular conditions below nc/4 where the Raman process appears to be enforced by Brillouin-driven ion-acoustic waves.