Striated jets due to nonlinear ponderomotive forces in laser produced plasmas at obliquely incident light

Abstract

An analysis is made of one of the expected nonlinear and anomalous mechanisms and instabilities in the corona of a laser irradiated plasma. As is well known, nonlinear ponderomotive forces generate a net acceleration of the plasma toward lower densities. It is demonstrated that the same forces at oblique incidence of the radiation, can cause a net motion perpendicular to the well-known forces along the density gradient: The standing wave generated that is split into zones (slabs) of the thickness of a quarter of a wave length, where the plasma is moving in the plane of incidence parallel and antiparallel to the slabs. This striated motion can also occur in an underdense plasma, while for the net acceleration toward lower density the strong change of the refractive index near the cutoff density is necessary. The striated parallel and antiparallel motion of the slabs is limited by the mean free path, by the velocity toward lower density and is determined by the condition of laminar and turbulent motion. The time constants on the order of picoseconds and the nonlinear absorption due to the generation of this striated motion are evaluated. Laser intensities exceeding 1013 W/cm2 incident at angles of 25° should build up striated jets with ion energies of a few keV.