ULTRASONIC STUDY OF HELIUM MIXTURES IN AEROGEL

Citation
M. Paetkau et J. Beamish, ULTRASONIC STUDY OF HELIUM MIXTURES IN AEROGEL, Czechoslovak journal of Physics, 46, 1996, pp. 153-154
Citations number
5
Categorie Soggetti
Physics
ISSN journal
00114626
Volume
46
Year of publication
1996
Supplement
1
Pages
153 - 154
Database
ISI
SICI code
0011-4626(1996)46:<153:USOHMI>2.0.ZU;2-1
Abstract
We have made ultrasonic measurements of He-3-He-4 mixtures confined in silica aerogel. By measuring changes in the ultrasonic attenuation an d velocity, the phase diagram for the system has been determined. The transition from the normal to the superfluid state is accompanied by a rapid increase in the ultrasonic velocity due to decoupling of the su perfluid fraction. A critical attenuation peak, which increases with f requency, is also seen at this transition temperature (Tc). For He-4 r ich mixtures, the beginning of phase separation (at Ts) is marked by a nother change in the velocity. Phase separation also results in hyster esis in the velocity and attenuation, but only at temperatures somewha t below the onset temperature Ts.