Shock-wave production and plasma motion in CO2-laser-irradiated targets

Abstract

We use visible-light, streaked shadowgraphy to make to first measurements of several transport and expansion phenomena in CO2-laser-irradiated foils. Measured velocities of the free-surface motion, produced by the laser-driven shock wave, at the foil’s rear surface yield shock pressures in reasonable agreement with theory. The velocity of plasma expansion from the absorption region is observed to change abruptly after ∼1.5 ns. We speculate that this effect is due to relaxation of the steepened plasma profile. Energy transport from the front to rear surface via the target’s edge, which complicated shock studies, is controllable with a simple shield.