Investigation of near critical point states of tantalum, lithium and sodium by pulse heating under launching
Vladimir Ya. Ternovoi, Dmitry N. Nikolaev, Sergey V. Kvitov, Alexey A. Pyalling and Anton N. Trukhanenokv
The near critical point states of liquid-vapor phase transition of tantalum, lithium and sodium were investigated. Heating of tantalum foil samples in 1-D geometry was carried out by multiple-shocked helium from a back side of a tantalum foil, and heating of lithium and sodium – by shocked helium from the front side under dynamically created isobaric conditions. The pressure was obtained from the measured shock velocity in helium using base length technique . The temperature of the sample was measured by a fast optical pyrometer. The heating histories of sample surface were analyzed. The state with the highest temperature before starting of plasma formation at pressures below the pressure of critical point of liquid–vapor transition is due to the state on a spinodal line. Intersection of the interpolating line of such states in a pressure range below critical point with such a line in the pressure range above the critical point allows us to evaluate the metal critical point temperature. Three sets of experiments with various histories of heating were carried out, which allowed us to evaluate the critical point location of the studied metals in p-Tplane.