Holographic interferometry of the interaction of a radially incident intense CO2laser beam (1011W/cm2, 38hyphen;nsec FWHM pulse) with an overdense heliumZhyphen;pinch plasma (negsim;1019e/cm3,Tesim;20 eV,L=100 mgr;m) has indicated the presence of a laserhyphen;driven shock. The radial dimension of the shock was found to be similar to the electron thermal conduction length, several times larger than the focalhyphen;spot dimension. Density structure within the shock was inferred from holographic interferograms. Heuristic considerations of the shock density ratio, the front thickness, and the shock velocity allowed for an estimate of 50ndash;80percnt; energy absorption.
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