Josephson Sound in Superfluid Helium.
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.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 27, 1996
- Accession Number
- ADA311131
Entities
People
- Richard Packard
Organizations
- University of California, Berkeley