Precision second-sound velocity measurements in helium II
- Cite this article as:
- Wang, R.T., Wagner, W.T. & Donnelly, R.J. J Low Temp Phys (1987) 68: 409. doi:10.1007/BF00682305
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The velocity of second soundu2 in helium II under its saturated vapor pressure was measured in an acoustic resonator with a typical precision of 0.07% and was found to agree with existing measurements. Data were taken from 1.135 to 2.09 K, with special attention given to the local maximum near 1.65 K, which can be used as a temperature reference point. A least squares cubic spline fit is given to the present data and selected data of other authors givingu2 from 0.55 K to within 60 µK of Tλ.