  A novel efficient scheme of acceleration and collimation of dense plasma is
proposed and examined. In the proposed scheme, a target placed in a cavity at
the entrance of a guiding channel is irradiated by a laser beam introduced into
the cavity through a hole and accelerated along the channel by the pressure
created and accumulated in the cavity by the hot plasma expanding from the
target and the cavity walls. Using 1.315-um, 0.3-ns laser pulse of energy up to
200J and a thin CH target, it was shown that the forward accelerated dense
plasma projectile produced from the target can be effectively guided and
collimated in the 2-mm cylindrical guiding channel and the energetic efficiency
of acceleration in this scheme is an order of magnitude higher than in the case
of conventional ablative acceleration.
