Experimental investigation of first- and second-sound shock waves in liquid helium II

The cryogenic shock tube is used to generate a gasdynamic shock which propagates through saturated helium vapor and subsequently reflects from the upper surface of a column of LHeII. Superconducting thin-film detectors, produced by evaporation of aluminum in an oxygen atmosphere, yield highly repeatable arrival time data for the incident gasdynamic shock and the resultant first- and second-sound shocks in the liquid. Accurate x-t diagrams of the shock trajectories have been constructed for initial liquid temperatures of T0 = 1.522, 1.665, 1.751, 1.832, 1.989, 2.031, and 2.0950K. Consistent discrepancies are observed between experimental and theoretical wave trajectories. The detector signals qualitatively verify theoretical predictions that the temperature decreases through the pressure shock and increases through the temperature shock. Amplitude measurements based on static detector calibrations indicate that the magnitude of the temperature jump across the pressure shock agrees approximately with the theoretical calculation. Temperature jump measurements for the coupled second-sound shock imply shock-induced relative velocities, w = v/sub n/ - v/sub s/, on the order of 2.5 m/sec. For initial conditions close to the lambda-transition (e.g., T0 = 2.0950K), the pressure jump across the first-sound shock is sufficient to cause a change in phase from LHeII to LHeI. This change is experimentallyevidenced by detector outputs indicating the absence of the temperature shock in the wake of a sufficiently strong pressure shock