Dynamics of inhomogeneous plasma expansion in intense femtosecond laser-ablated aluminum plumes

Dynamics of an inhomogeneous plasma expansion generated by intense fs laser radiation from a metal Al foil was investigated experimentally and simulated numerically. A shock wave-like structure moving at a constant velocity V ≈ 1.5·10
⁷
cm/s (close to ion-acoustic one) was observed and explained as a quasi-electrostatic collisionless shock owing to inhomogeneous pre-plasma swept by a flow of hot electrons.