<title>Evaluation of irradiation uniformity on spherical target using angularly dispersed, partially coherent light in direct-drive laser fusion</title>

Abstract

In order to improve an irradiation uniformity on a spherical target, an amplified spontaneous emission (ASE) with an angular dispersion of spectrum is introduced in Gekko XII laser system. The irradiation nonuniformity was estimated from a measured beam pattern at the equivalent target plane. The ASE light substantially reduces the irradiation nonuniformity (rms value) from 19.7% to 3.8%. We also theoretically analyzed smoothing characteristics of the ASE light, and compared them with the experimental results. The Legendre-mode-dependent reduction rates of irradiation nonuniformities which are determined by the ratio of mode amplitudes with and without introduction of ASE, were very consistent with theoretical predictions.