Work on laser interaction and implosion at Centre d'Etudes de Limeil

Laser-matter interaction experiments at 1.06 and 10.6μm were performed at fluxes of 5x1015 and 3x1013Wcm-2, respectively. At 1.06μm the penetration depth of the absorbed energy, studied with the aid of stratified plane targets, is several thousand A. 2-MeV Al11+ ions and 50-500-keV electrons were observed at 10.6μm. Two types of implosion experiments were carried out with glass microballoons (diameter approximately 100μm, thickness approximately 1μm) containing about ten bars of DT at 1.06μm and at absorbed energy densities of the order of 50Jμg-1. In the case of the Iris experiment, performed at 1013Wcm-2, implosion seems to be due to progressive ablation of the wall of the microballoon. The Coquelicot experiment was performed with the P.102 laser at several times 1015Wcm-2 and with a pulse of 40-80ps. From diagnostic tests, especially observation of the X-rays emitted, the following characteristics were deduced: energy absorbed by the target, 4J; temperature and density of the compressed DT, 1keV and 0.2gcm-3, product rhor approximately 10-4gcm-2; neutron yield, 105. To interpret these experiments, theoretical studies were performed on radiation pressure, particle transport, relativistic effects and implosion stability; one- and two-dimensional implosion codes have been developed. The implosion experiments will be continued with the Octal laser (700J-2TW-8beams) whose shaped pulse can be varied from 50ps to 1ns. (author)