EFFECT OF LATERAL ENERGY TRANSPORT ON ION EXPANSION ENERGY SCALING IN LASER-PRODUCED PLASMAS.

Polythene targets have been irradiated at a maximum flux of 10**1**4W/cm**2 with a focused Nd:glass laser. Spatial extent of the lateral energy transport as a function of the incident laser intensity has been determined using pinhole camera imaging with 12- mu m spatial resolution. The effect of lateral energy transport on the plasma expansion energy scaling has been investigated. The scaling is significantly affected at higher intensities for a smaller irradiation spot. It is shown that the lateral flow of the plasma energy in laser-plasma interaction plays an important role and modifies the plasma expansion energy scaling. Lateral transport becomes less effective if the laser spot diameters are kept large. For small laser spot irradiation and moderate intensities below 5 multiplied by 10**1**3W/cm**2, a rapid diffusion of hot thermal plasma from the laser-plasma interaction region appears to be responsible for the observed transport.