Experimental study of transient evaporation of superfluid helium induced by incidence of second sound thermal pulse onto free surface

Transient evaporation phenomena in superfluid helium (He II, T < 2.17 K) environment are investigated. We can take such great advantages of He 11 environment that a practically pure vapor-liquid system can be realized in the experimental cell because all gaseous components except helium are in frozen state and a temperature shock wave can be used as a pulsed heat source for evaporation. Evaporation is caused by the incidence of a second sound thermal shock onto the free surface. The whole gas-dynamic phenomena are visualized with the laser holographic interferometer and are measured with superconductive thermometers and pressure transducers as well as with the newly developed superconductive hot wire. It is seen that the evaporation wave turns into a weak shock wave. It is confirmed that the Rankine-Hugoniot relation holds among the gas-dynamic quantities measured in the evaporation wave portion. The condensation coefficient of He 11 is obtained from the comparison of the experimental data with the slip boundary condition at evaporating interface derived from the kinetic theory of gases. (C) 2002 Elsevier Science Inc. All rights reserved.