DYNAMICS AND STABILITY OF AN EXPANDING LASER-INDUCED PLASMA IN A LOW-DENSITY GAS

Experimental studies of a laser-produced metal plasma expansion into a gas with a mass density of 0.1-30 mug/cm3 have been performed using s treak-camera imaging. The results show that plasma expansion dynamics can be described by a snowplow model with a dimension factor dependent on the laser focal spot shape. It has been.shown that the plasma boun dary becomes unstable at the moment of maximum deceleration (of the or der of 10 cm/mus2), and the evolution of boundary perturbation has bee n monitored. An explanation of the observed effect on the basis of Ray leigh-Taylor instability is proposed and confirmed by comparison of si mple model predictions with experimental evidence. The evolution of th e plasma-front profile has been observed for the times 0 < t < 10 gamm a-1, where gamma is the instability increment. Competition of differen t unstable modes has been observed.