Laser wavelength effect on the thermal conductivity and ablation in plasmas created by a laser

Theoretical and experimental results are presented from a study of the thermal effects of the laser-matter interaction with a D-T pellet in inertial confinement fusion trials. Attention is focused on the ablation pressure, the flux of the ablated mass from the pellet shell, and the hydrodynamic efficiency, with consideration given to inhibition of thermal conductivity in the laser-plasma interaction. The effects of a magnetic field and electromagnetic or ion acoustic instabilities on the thermal conductivity are analyzed. Limitations imposed on the thermal conductivity are demonstrated to alter the density profile, the velocity, and the temperature near the critical density. Models for flows with a spherical geometry are compared for differences in scaling the macroscopic parameters with respect to the wavelength of the laser beam, the laser flux, and the degree of thermal inhibition. A method of thin sheets was used to examine the problem experimentally. It is concluded that short wavelength lasers are preferred for laser fusion operations.