Fast-electron transport in high-intensity short-pulse laser-solid experiments

The interaction of short-pulse (less than or equal to 1 ps) high-intensity (approximate to 10(18) W cm(-2)) lasers with solid targets generates large numbers of energetic (approximate to 100 keV) electrons. The energetic electrons can only penetrate into the solid if the solid can supply an equivalent charge-neutralizing return current. We develop a simple model which shows that in many cases the solid cannot support the required return current and the fast electrons are confined by electric fields to the surface of the target. The target response to laser irradiation depends strongly on the electrical conductivity of the solid.