Third sound in He films on copper substrates

M.E.W. Eggenkamp(1), J.P. van Best(1), P.W.H. Pinske(2), V. Schwarts(3), R. Jochemsen(1), G Frossati(1)

(1) Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9506, 2300 RA Leiden, The Netherlands.
(2) Van der Waals-Zeeman Laboratory, University of Amsterdam,
Valkenierstraat 65-57, 1018 XE Amsterdam.
(3) Verkin Institute for Low Temp. Physics, 47 Lenin Avenue, Kharkov 310164 Ukraine.

We have performed simultaneous measurements of the speed and attenuation of a third sound wave on a glass and on a copper resonator. The third sound wave on the copper substrate is much more difficult to excite with a thermal method, and we can only see third sound waves on the copper substrate for helium films thicker than 14 atomic layers. The measurements were done to prepare for third sound measurements in 3He films on a copper substrate below 1 mK. A cell has been prepared to used electromechanical excitation of the third sound waves which is suitable for these thicker films, and which avoids the extra heat input of the thermal excitation. With a small vibrating wire the difference in superfluid transition temperature between bulk 3He and 3He films can be determined.
Communications from the Kamerlingh Onnes Laboratory 1996

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