"Phase freezeout" in isentropically expanding matter

Abstract

Features of isentropic expansion of warm dense matter (WDM) created by intense energy fluxes (strong shock compression or instant isochoric heating by laser or heavy ions) are under discussion in situation when ($i$) -- thermodynamic trajectory of such expansion crosses binodal of liquid-gas phase transition, and ($ii$) -- expansion within the two-phase region is going along equilibrium branch (not metastable one) of the two-phase mixture isentrope. It is known in the plane case that because of break in the expansion isentrope at binodal point (in $P-V$ plane) i.e. jump of sound velocity in this point, there appears extended zone ("boiling layer") of uniformity in expanding material with constant thermodynamic and kinematic parameters. It corresponds just to the state on this binodal of boiling liquid. The point is that because of self-similarity of such expansion (in plane case) this boiling layer contains finite and fixed part of whole expanding material. This property makes it possible (at least formally) to discuss this type of isentropic expansion of WDM as a tool for generation (and diagnostics) of extended uniform state of matter exactly on binodal (and even in critical point) when parameters of this binodal (and/or thermophysical properties on it) are not known. It is natural to use the term "phase freezeout" for this regime of expansion. It is similar to the terms "chemical freezeout" and "kinetic freezeout", which are widely used in interpretation of quark-hardon transformations during expansion of quark-gluon "fireball" in ultra-high energy ionic collisions in supercolliders. General hydrodynamic scheme of adiabatic movements for the case of ensemble of well positioned plates or foils (stack target) under instant isochoric heating (for example, by heavy ion beam) is considered as elaboration of simple idea of phase freeze-out ("reverberation" regime).