Irradiation uniformity for high-compression laser-fusion experiments

High-compression direct-drive laser-fusion experiments require the rms laser-irradiation nonuniformity to be below the 1%–2% level. The combination of two-dimensional smoothing by spectral dispersion (SSD), phase plates, polarization smoothing, and beam overlap are shown to be sufficient to reach this goal. Here is presented a discussion of the mathematical formalism of two-dimensional SSD with numerical calculations illustrating the factors that affect irradiation uniformity. The levels of uniformity that can be achieved on the OMEGA laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] at the University of Rochester and at the National Ignition Facility (NIF) [Paisner et al., Laser Focus World 30, 75 (1994)] being built at the Lawrence Livermore National Laboratory are examined.