RECENT PROGRESS IN LASER FUSION-RESEARCH AT OSAKA-UNIVERSITY - UNIFORMITY AND STABILITY ISSUES

Improvement of laser irradiation uniformity in the Gekko XII system [I EEE J. Quantum Electron. QE-17, 1639 (1981)], both single beam pattern and power balance, is discussed. Substantial reduction of laser absor ption nonuniformity is obtained for spherical harmonic modes greater t han 15 by introducing spectrally dispersed amplified spontaneous emiss ion. No perturbation growth is observed in flat foils accelerated by s pectrally dispersed amplified spontaneous emission. Dependences of las er absorption uniformity on beam pattern and power imbalance are inves tigated in detail. The design goal of the power imbalance in the preci sion Gekko XII system is 3% in peak to valley, and laser absorption no nuniformity is estimated to be a few percent. Growth of hydrodynamic i nstabilities is analyzed for high convergence ratio implosions in the precision Gekko XII system.