ENERGY AND NONLINEARITY CONSIDERATIONS FOR THE ENHANCED PLASMA-WAVE MODEL OF RAMAN-SCATTERING - COMMENT

The interpretation of some recent experiments [Phys. Rev. Lett. 60, 1018 (1988); Phys. Fluids 30, 1795 (1988)] by Simon and Short [Phys. Fluids B 1, 1073 (1989), referred to as SS4] is discussed. The predicted angular distribution is almost narrow enough to correspond to the data discussed in SS4, but not to correspond to data from previous experiments having similar plasma-wave damping but much smaller density-gradient scale length. Examination of the time dependence of the Raman spectrum in all the data, rather than only the single case discussed in SS4, shows that the hydrodynamic behavior, rather than the vanishing of quarter critical, determines the time of maximum emission. Finally, it is notable that the analysis of the power flow in SS4 requires that most of the laser energy be converted into intense electron beams with narrow velocity distributions having intensities of 20x the average laser power. Though not impossible, this seems unlikely. © 1989 American Institute of Physics.