Scaling of laser-plasma interactions with laser wavelength and plasma size

This chapter reports on work done at the Lawrence Livermore National Laboratory which demonstrated that plasma size is an important parameter in wavelength-scaling experiments because it determines both the threshold and potential gain for a variety of laser-plasma instabilities. Topics covered include thresholds for instabilities, Raman scatter, stimulated Brillouin scatter, two-plasmon decay instability, filamentation due to ponderomotive force, Raman scatter in an Argus laser experiment, evidence for strong instabilities in a Shiva laser experiment, filamentation in Argus laser experiments, thermal filamentation, and the role of inhomogeneities on the incident laser beam. It is graphically illustrated that a concerted effort is needed to field experiments with larger plasmas, so as to begin approaching the parameters typical of reactor-scale targets. The evidence presented for Raman scatter, filamentation, and the two-plasmon decay instability needs to be confirmed in experiments which measure several instability signatures simultaneously, and which produce more quantitative information about the local density and temperature profiles. Includes 4 photos and a diagram