Laser-Plasma Coupling with Ignition-Scale Targets: New Regimes and Frontiers on the National Ignition Facility

Abstract

It is very exciting that the National Ignition Facility (NIF) is now operational and being used to irradiate ignition-scale hohlraums. As discussed in the last Scottish Universities Summer School in Physics on the topic of laser-plasma interactions in 2005, laser plasma physics faces its biggest challenge ever on NIF. Excellent temporal and spatial control of the laser energy deposition is required for highly convergent implosions, while many new regimes are being accessed. These new regimes include much larger plasmas and laser beam spots, many crossing laser beams, and interaction physics in highly shaped laser pulses. Furthermore, it is key that a broad range of plasma conditions be accurately modelled in the design codes in order that the laser plasma interactions be correctly modelled. Indeed, all these new regimes have proved to be significant challenges and to require new and ongoing understanding. There are many fascinating trade-offs. For example, crossing beam effects both provide a convenient tool to quickly provide the laser beam balance needed for moresymmetric implosions but also enhance the stimulated scattering of the incident laser light. The impact of these new coupling regimes in recent NIF experiments is discussed, and the ongoing understanding outlined.