Accession Number : AD0775899

Title :   Third Sound Velocity and Attenuation Below 1.2 Degrees Kelvin.

Descriptive Note : Technical rept.,

Corporate Author : CALIFORNIA UNIV LOS ANGELES DEPT OF PHYSICS

Personal Author(s) : Scholtz,John Henry

Report Date : DEC 1973

Pagination or Media Count : 153

Abstract : The velocity of third sound on glass and CaF2 substrates and at a variety of film thicknesses has been measured using a He3 cryostat from temperatures of 1.2K down to 0.5K. Then with a dilution refrigerator the results on glass were extended to 0.1K. The third sound was generated and detected thermally in the usual manner, and the velocity was determined by measuring the time of flight of a pulse. Film thicknesses are found by measuring the chemical potential of the film at 1.5K. Third sound has now been ovserved in films as thin as 2.1 atomic layers, and hence indicates the existence of superfluidity in two dimensional systems. The attenuation of third sound on glass has been measured as a function of frequency at temperatures from 1.2K down to 0.7K and over a variety of film thicknesses. (Modified author abstract)

Descriptors :   *Superfluidity, Liquid helium, Films, Cryogenics, Calcium fluorides, Glass

Subject Categories : Physical Chemistry
      Thermodynamics

Distribution Statement : APPROVED FOR PUBLIC RELEASE