Accession Number : AD0429898

Title :   FOURTH SOUND IN HELIUM II,

Corporate Author : CALIFORNIA UNIV LOS ANGELES

Personal Author(s) : Rudnick,I. ; Shapiro,Kenneth A.

Report Date : JAN 1964

Pagination or Media Count : 48

Abstract : Fourth Sound is a pressure and density wave in Helium II, in which only the superfluid is in motion. The existence of this wave mode has been substantiated experimentally by measuring the frequency of a plane wave resonance in a closedclosed cylindrical acoustic resonator, as a function of the absolute temperature. The resonator was filled with a porous medium which allowed only superfluid motion. The velocity values, which were derived from the frequency data, agree to 1% with the temperature dependence predicted theoretically. The absolute value of the Fourth Sound velocity is affected by the coherent multiple scattering of the wave from the superleak material. An empirically determined correction predicts the effect of multiple scattering, as a function of superleak porosity, to 3%. The theoretical multiple scattering fomulae yield results which are correct in sign, but not in magnitude. (Author)

Descriptors :   (*HELIUM, ACOUSTIC PROPERTIES), PRESSURE, MECHANICAL WAVES, DENSITY, EXPERIMENTAL DATA, CRYOGENICS, ELECTRONIC EQUIPMENT, ACOUSTIC EQUIPMENT, VELOCITY, SCATTERING, CORRECTIONS, PROPAGATION, TABLES(DATA)

Distribution Statement : APPROVED FOR PUBLIC RELEASE