Heating by Raman Backscatter and Forward Scatter

This Letter presents computer simulations of the reflection and heating due to stimulated Raman scattering of intense laser light in large regions of underdense plasma. The heated electron distribution is approximately a Maxwellian of temperature $\frac{1}{2}{m}_e{v_p}^2$. A simple model of the reflection is presented. Forward Raman scattering was also observed producing extremely energetic electrons. Finally, two-dimensional simulations showed sizable Raman scattering coexisting with heating by the $2{\omega }_{\mathrm{pe}}$ instability. Raman scattering may cause a preheat problem with large laser-fusion-reactor targets.