Rarefaction wave and gravitational equilibrium in a two-phase liquid-vapor medium

Abstract

The problems studied in this paper involve the action of laser radiation or a particle beam on a condensed material. Such an interaction produces a hot corona, and the recoil momentum accelerates the cold matter. In the coordinate frame tied to the accelerated target, the acceleration is equivalent to the acceleration of gravity. For this reason, the density distribution ρ is hydrostatic in the zeroth approximation. In this paper the structure of such a flow is studied for a two-phase equation of state. It is shown that instead of a power-law density profile, which obtains for a constant specific-heat ratio, a complicated distribution containing a region with a sharp variation of ρ arises. Similar characteristics of the density profile arise with isochoric heating of matter by an ultrashort laser pulse and the subsequent expansion of the heated layer. The formation of a rarefaction wave and the interaction of oppositely propagating rarefaction waves in a two-phase medium are studied. It is very important to take account of the two-phase nature of the material, since conditions (p a ∼1 Mbar) are often realized under which the foil material comes after expansion into the two-phase region of the phase diagram.