Thresholds of Convective Raman Backscattering: Effects of∇n, Thomson Scattering, Noise, Collisions, and Landau Damping

Using kinetic simulations we find that Raman backscattering can exist for laser intensities a factor 2π lower than the density gradient (∇n) threshold and that Thomson scattering can account for backscattering signals even lower. In addition, kinetic, collisional simulations show that laser intensities {}3-10 times the electron-ion collisional threshold are needed for significant Raman absorption. Collisions can also reduce the heated electron temperatures for ∇n≠0.