Laser smoothing and imprint reduction with a foam layer in the multikilojoule regime.

This Letter presents first experimental results of the laser imprint reduction in fusion scale plasmas using a low-density foam layer. The experiments were conducted on the LIL facility at the energy level of 12 kJ with millimeter-size plasmas, reproducing the conditions of the initial interaction phase in the direct-drive scheme. The results include the generation of a supersonic ionization wave in the foam and the reduction of the initial laser fluctuations after propagation through 500 mum of foam with limited levels of stimulated Brillouin and Raman scattering. The smoothing mechanisms are analyzed and explained.

Generation of 20-TW pulses of picosecond duration using chirped-pulse amplification in a Nd:glass power chain.

Pulses of 20-TW peak power have been generated at 1064 nm using the chirped-pulse-amplification technique with a 90-mm output-aperture Nd:silicate glass amplification line. This system delivers 60 J of energy in a chirped pulse of 600-psec duration, with a capacity to maintain a 3.5-nm output bandwidth. These chirped pulses are compressed to 1.2 psec with an energy of 24 J by using large holographic gold-coated 1740-lines/mm diffraction gratings.