Particle-in-cell simulations of stimulated Raman scattering for speckled lasers with temporal bandwidth*

Stimulated Raman scattering (SRS) has been studied using large-scale multi-dimensional particle-in-cell (PIC) simulations with parameters relevant to initial confinement fusion (ICF) experiments.  More realistic laser profiles are modeled by including laser speckles without and with temporal beam smoothing such as induced spatial incoherence (ISI) and smoothing by spatial dispersion (SSD), and Spike Train of Uneven Duration and Delay (STUD pulses). Simulation results show that the reflectivity from SRS can be reduced with laser bandwidth comparable to the temporal growth rate of the instability. Kinetic effects such as “inflation” have been found to be important for SRS even with high (6THz) laser bandwidth in two dimensions. Other schemes for mitigating SRS including the use of transverse magnetic fields will be discussed.