Kinetics of the Raman Instability in a Laser Plasma

The phase space evolution in a non-relativistic and homogeneous laser plasma in the presence of the stimulated Raman scattering is investigated. The mechanism of the electron acceleration in the potential wells of the plasma wave accompanying the Raman backscattering is analyzed by Vlasov-Maxwell simulations. In addition to the interaction with the primary wave a cascading is observed consisting in a secondary scattering of the primary Raman backscattered wave. The corresponding backward propagating plasma wave can accelerate electrons away from the target against the direction of the heating laser beam. Moreover, there is an indication of a non-linear quasi-mode combined from both the electrostatic waves with a strong tendency for trapping. The transform method is used for a solution of the set of partial differential equations which consists of the Vlasov equation and of the full set of Maxwell equations. To overcome numerical instabilities during the simulation, a simplified Fokker-Planck collision term was introduced.