Study ofNon-linear Wave and Quantum Phase Transition Phenomena in Superfluid Helium Performed in Superfluid Shock Tube Facility

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The quality of the compression nand thermal shock waves generated in the superfluid shock tube facility was found to be satisfactorily high enough for general shock wave researches. It was found that the temperature dropped in a compression shock wave and the intensity of thermal shock waves were very strong compared with those generated by pulsed heating in HeII.The velocity of the uniform flow behind a compression shock could be calculated from the visualization image with the ultra high speed video. The Reynolds number of the flow was extremely high, as high as the order of 107. This result indicates that the facility may be an alternative to the super fluid wind tunnel.The physical state of the shock compressed state at a shock front generally obeys an isentropic process in the case when the initial state of liquid helium is far from the lambda point. It is, however, found that considerable entropy production is induced in the vicinityofthe lambda line in the case where the initial equilibrium state of liquid helium is close to the lambda point. The excess entropy production was roughly in proportion to the temperature difference from the lambda point temperature.It is found from the high speed pictures that a strong density fluctuation was induced behaind a compression shock while crossing the lambda line.Some experiments are/conducted toward the experiments for solidification of He II.