Optimization of irradiation configuration in laser fusion utilizing self-organizing electrodynamic system

A simple numerical method to determine an optimum beam configuration for highly uniform irradiation is proposed for direct-drive laser fusion systems and is applied to an arbitrary number of laser beams, NB. Driven by the Coulomb repulsion force, NB randomly distributed like charges move on a spherical surface to settle with a stable configuration having the minimum Coulomb energy for the system. Such resultant charge configurations practically do not depend on the initial conditions, and thus the solutions are very robust and unique. The irradiation uniformity is numerically assessed by overlapping NB beam patterns and calculating the laser absorption based on various spatial absorption patterns for the individual beams. The present method provides some improved illumination configurations for laser fusion compared with previously proposed designs. In particular, new coordinates for N-B=48 and 72 are found to give an extraordinarily higher uniformity than for other numbers of NB. The influence of system imperfection on the irradiation uniformity is also discussed. (C) 2010 American Institute of Physics. [doi:10.1063/1.3467497]