Vlasov simulations of trapping and inhomogeneity in Raman scattering

摘要

We study stimulated Raman Scattering (SRS) in laser-fusion plasmas with the Eulerian Vlasov code ELVIS. Backward SRS occurs in sub-picosecond bursts and far exceeds linear theory. Forward SRS and re-scatter of backward SRS are also observed. The plasma wave frequency downshifts from the linear dispersion curve, and the electron distribution flattens. This is consistent with trapping and reduces Landau damping. There is sonic acoustic (omega proportional to k) activity and possibly stimulated electron acoustic Scatter. Kinetic ions do not affect SRS for early times but suppress it later on. SRS from inhomogeneous plasmas exhibits a kinetic enhancement for long density scale lengths. More scattering results when the pump propagates towards a higher as opposed to towards a lower density.