Analysis of laser-plasma coupling and hydrodynamic phenomena in long-pulse, long-scale-length plasmas

Near-reactor-size, laser-plasma conditions are studied at Iλ² values of 10¹⁴ W/cm² {μ}m² with 1-mm-size plasmas, 3-kJ, 3-ns irradiations on the 1.064-{μ}m Shiva laser. Laser-plasma-coupling issues, such as the competition between stimulated Brillouin scattering and inverse bremsstrahlung absorption and the generation and transport of hot electrons, are addressed. Hydrodynamic phenomena of relevance to direct-drive laser fusion targets are also studied, including the following: the pressures, mass ablation rates, and target velocities achieved; the lateral transport of laser energy away from the initial illumination spot; and the thermal smoothing of laser nonuniformities due to the moderate intensity and the long-pulse-length--induced separation of the critical surface from the ablation surface.