Stimulated Compton backscatter from free electrons in laser−induced fusion plasmas

Stimulated Compton backscatter of incident Nd:glass laser photons (h/ω≃ 1 eV) from free electrons (n<1019/cm3 at κT ≃ 103 eV) in laser−induced fusion plasmas is investigated. The threshold for stimulated amplification of reflected radiation against spontaneous loss is 109 W/cm2 incident intensity while the low gain of the system determines the threshold effectively at 1015 W/cm2. For 5×1018 free electrons/cm2 in the plasma, steady state reflectivities of 10−4 are calculated for 1016 W/cm2 incident intensity. This results from the gain being driven to small values when stimulated photon scatter dominates particle collisions and thereby tends to level the resonant scattering interval of the electron momentum distribution. At lower incident intensities or on the time scales of the transients, interesting experiments might be designed to examine this phenomenon.