NONLINEAR CONFINING AND DECONFINING FORCES ASSOCIATED WITH INTERACTION OF LASER RADIATION WITH PLASMA

The nonlinear interaction of an intense light wave with an inhomogeneous plasma produces a mac-roscopic motion. A rigorous treatment of this interaction based on the ponderomotive force descrip-tion leads to a general equation of motion. In a plasma with collisions and high electron density, the resulting force density can be interpreted as an expression of the radiation pressure. Below special densities there results a nonlinear collisionless force whose direction is toward decreasing density, and which produces a deconfinement. The magnitude of this force has a polarization dependence only in the third-order terms of the spatial dependence of the density. The total deconfining recoil momentum transferred to the inhomogeneous transition layer is evaluated. The theory of the nonlinear collisionless acceleration is used to explain the experimentally observed properties of the fast part of plasmas produced by lasers from isolated single small aluminum balls and thick solid targets.