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
Solid State Physics
Distribution Statement : APPROVED FOR PUBLIC RELEASE