Accession Number : ADA311131

Title :   Josephson Sound in Superfluid Helium.

Descriptive Note : Annual rept. 1 Jun 95-31 May 96,

Corporate Author : CALIFORNIA UNIV BERKELEY DEPT OF PHYSICS

Personal Author(s) : Packard, Richard

PDF Url : ADA311131

Report Date : 27 MAY 1996

Pagination or Media Count : 6

Abstract : This project is directed toward detecting and quantifying a new physical phenomenon characterized by an acoustical field generated near a submicron aperture by quantized phase slip events in superfluid (4)He. The sound frequency is determined by the Josephson frequency relation. We have developed several techniques and devices including: a system which can drive superfluid through the aperture at constant pressure head (Josephson frequency) as small as 10(exp -4) Pa; an improved cryogenic valve to isolate the acoustic cavity; a vacuum-backed cryogenic microphone with adequate sensitivity to detect the phenomenon; a vibration isolation system. Preliminary experiments have revealed a source of non-acoustic pressure drop which has lead to a new understanding of dissipation within the cell. Measurements have also revealed a new insight into the intrinsic critical velocity near T.

Descriptors :   *SOUND, *HELIUM, *JOSEPHSON JUNCTIONS, *SUPERFLUIDITY, FREQUENCY, VIBRATION ISOLATORS, REDUCTION, ACOUSTIC RESONATORS, PRESSURE, VALVES, CRYOGENICS, ACOUSTIC FIELDS, CAVITY RESONATORS.

Subject Categories : Inorganic Chemistry
      Physical Chemistry
      Acoustics
      Fluid Mechanics
      Solid State Physics
      Thermodynamics

Distribution Statement : APPROVED FOR PUBLIC RELEASE