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 {μ}g/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/{μ}s²), 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 0t10γ^-1, where {γ} is the instability increment. Competition of different unstable modes has been observed.