Two-dimensional multi-lens array with circular aperture spherical lens forflat-top irradiation of inertial confinement fusion target

A two-dimensional multi-lens array 350 mm in diameter with spherical elemen t lenses has been tested to improve the irradiation uniformity of a high po wer glass laser for inertial confinement fusion (ICF). A circular shape for the element lens aperture is chosen to eliminate azimuthally asymmetric in tensity distribution. An approximate hat-top intensity distribution is obta ined with a lens array of 37 lenses. Beam patterns of a coherent laser and partially coherent light (PCL) with the random phase plate (RPP) and the mu lti-lens array (MLA) are measured in a GEKKO XII glass laser system. Spheri cal mode structure of the irradiation nonuniformity of 5.6% with MLA is est imated with cos(3) theta distribution of absorption coefficient in the targ et plasma.