Toward improved characterization of laser plasma coupling in NIF-scale plasmas

To date laser plasma coupling has been ``good enough'' (i.e., gives sufficient drive as well as sufficiently controllable symmetry) to enable numerous well-diagnosed NIF implosion experiments. On a longer time scale, an improved characterization of laser plasma coupling in NIF-scale plasmas is desirable both for ignition and other high energy density physics experiments. Important issues include the time-dependence of the cross beam energy transfer, the role of stimulated sideward scattering of laser light in the hohlraum, overlapping beam effects on stimulated scattering, the efficiency with which quarter-critical density instabilities generate superhot electrons, and the evolving plasma conditions within the hohlraum. Simple experiments to address some of these issues are discussed.