A SPECIFIC HEAT AND FOURTH SOUND MEASUREMENT OF SIZE EFFECTS IN LIQUID HELIUM.
CALIFORNIA UNIV LOS ANGELES DEPT OF PHYSICS
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An experimental and theoretical investigation of liquid helium confined to the small pores of highly compressed powders was made in order to investigate size effects in liquid helium. The specific heat measurements show that the bulk specific heat singularity is replaced by a flattened peak that is shifted towards lower temperatures with decreasing pore size. The theory of second order phase transitions was used to calculate the specific heat of liquid helium in finite systems. The superflow onset temperature and the super fluid fraction were determined from fourth sound hydrodynamic pressure waves measurements in the same powders in which specific heat measurements were made. The onset temperature and the temperature of the specific heat peak are equal within experimental error. Author