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 streak-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 boundary becomes unstable at the moment of maximum deceleration (of the order of 10 cm/mus2), and the evolution of boundary perturbation has been monitored. An explanation of the observed effect on the basis of Rayleigh-Taylor instability is proposed and confirmed by comparison of simple model predictions with experimental evidence. The evolution of the plasma-front profile has been observed for the times 0 < t < 10 gamma-1, where gamma is the instability increment. Competition of different unstable modes has been observed.