Plasma Formation on the Front and Rear of Plastic Targets due to High-Intensity Laser-Generated Fast Electrons

Novel features of plasma generation by 1 ps, $1\mu \mathrm{m}$, $\sim {10}^{19}\mathrm{W}{\mathrm{cm}}^{-2\mathrm{}}$ laser pulses on thick plastic targets are presented: (i) The electron distribution in the ablated plasma has a minimum along the target normal which persists long after the laser pulse $(>1\mathrm{}\mathrm{ns})$; (ii) a narrow plasma jet is formed at the rear surface after a few picoseconds, in line with the laser focus. This is consistent with a beam of fast electrons traveling through the target, collimated by a magnetic field in the target.