Effect of laser pulse group velocity on ion acceleration from transversely expanded plasma foil in radiation pressure dominant regime

Abstract

We have analytically and numerically analysed the interaction of an ultra-intense laser pulse with ultra thin dense plasma foil in the radiation pressure dominant (RPD) regime taking into account the group velocity of the laser and the transverse expansion of the target. The group velocity decreases and the transverse expansion increases the ion energy. As the group velocity reduces the transverse expansion due to the early termination of the acceleration process, its effect dominates the transparency.