Abstract
The results of an experimental investigation of the evolution of planar, non-linear, second-sound pulses in superfluid4He, to within 650 nK of the λ-transition, are presented. A new method for extracting the second-sound velocity and damping is demonstrated. As predicted from two-fluid hydrodynamics, the pulses are well modeled by the solutions of Burgers' equation. The second-sound velocity (u 20) and damping (D 2) are extracted from fits of the model to the data. Damping data are obtained in this fashion to 3×10−7 in reduced temperature at saturated vapor pressure; nearly two decades closer to Tλ then any previous measurements. The superfluid density is extracted from theu 20 measurements and the critical exponent, ζ, is determined. A study of very large amplitude pulses near Tλ is also presented. These pulses extend well beyond the range of validity of Burgers' equation. The amplitude of the shock that forms at the trailing edge of the pulse is observed to saturate as a function of heater power and then decrease suddenly, as has been previously observed away from Tλ. However, the pulse shapes are quite different from any previously observed.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
