Ultrasonic studies of helium in porous glasses

Conference · Wed Oct 25 00:00:00 EDT 1989 · AIP Conference Proceedings (American Institute of Physics); (USA)

OSTI ID:7188314

Beamish, J R; Mulders, N ^[1]

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1. Department of Physics Department Of Astronomy, University of Delaware, Newark, DE 19716, USA (USA)

We have used an ultrasonic technique to study the critical behavior of superfluid {sup 4}He in porous Vycor glass and in a silica aerogel. We determine the superfluid density from the increase in the transverse sound velocity when the superfluid decouples and the damping from the corresponding attenuation. At the lowest frequencies (around 3 MHz), we observe transitions (considerably sharper in aerogels than in Vycor) with critical exponents similar to those found in torsional oscillator measurements. At higher frequencies the transitions become noticeably rounded (by as much as 0.1 K at 196 MHz in Vycor). In addition, there are clear attenuation peaks at the transitions and these also broaden and shift to higher temperatures as the sound frequency increases. We compare our results for full pores and for films to other experiments and discuss recent theories of the superfluid transition in porous media.

• OSTI ID: 7188314
• Report Number(s): CONF-8904257--
• Journal Information: AIP Conference Proceedings (American Institute of Physics); (USA), Journal Name: AIP Conference Proceedings (American Institute of Physics); (USA) Vol. 194:1; ISSN 0094-243X; ISSN APCPC
• Country of Publication: United States
• Language: English

Related Subjects

640450* -- Fluid Physics-- Superfluidity
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ATTENUATION
EVEN-EVEN NUCLEI
FILMS
FLUIDS
HELIUM 4
HELIUM II
HELIUM ISOTOPES
ISOTOPES
LIGHT NUCLEI
MATERIALS
NUCLEI
PHASE TRANSFORMATIONS
POROUS MATERIALS
QUANTUM FLUIDS
SOUND WAVES
STABLE ISOTOPES
TEMPERATURE MEASUREMENT
VORTICES
VYCOR