Uniform illumination of spherical laser fusion targets

Uniformity of illumination of spherical laser fusion targets is calculated for eight, twelve, and twenty beams arranged according to the symmetry of the Platonic solids. Uniformity is optimized by varying the f/no of ideal aberration-free lenses, amount of beam overlap, and the shape of the spatial beam profile. The numerical results show twenty-beam illumination to be slightly better than twelve-beam illumination, with eight beams running a poor third. Refractive energy losses due to nonorthogonal illumination and the implications for the design of a practical laser fusion reactor are discussed.