Superfluidity of Liquid Helium-4
About the experiment
Helium gas liquefies at 4.2 K at atmospheric pressure. When it's cooled to lower temperatures, there is a phase transition at 2.17K to a new liquid phase which exhibits the property of superfluidity. The superfluid has the properties of a Bose-Einstein condensate: extraordinarily low viscosity and nearly infinite thermal conductivity. Heat propagates as a wave called second sound. Using an acoustic resonator, you will measure the speed of sound in gases and in liquid helium. In the superfluid phase, you will measure the speed of second sound as a function of temperature. You can show that the speed of second sound becomes quite slow at the superfluid-normal fluid transition (the lambda point).. This experiment uses a phase-sensitive lock-in detector to measure standing wave resonances in a cylindrical acoustic cavity. You will also learn how to handle cryogenic fluids such as liquid nitrogen and liquid helium.
What you will learn
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Experience with liquid helium and cryogenics
Preparation
Required reading:
Recommended reading:
- R.J. Donnelly, The Two-Fluid Theory and Second Sound in Helium, Physics Today 62, 34 (2009)
- J Wilks, Theory of Liquid Helium, Rep. Prog. Phys. 20, 38 (1957)
- R.J. Donnelly, The Discovery of Superfluidity, Physics Today 48 (30), 1995.
- Acoustics of the Cylindrical Resonator
- Second Sound in Helium II by Chodosh, Hiatt, Shah, and Yan (2008)
- Data - heat capacity and velocity of second sound in helium 4
Supplementary materials
- About Lock-in Amplifiers (SRS Tech Note)
- Signal Enhancement (SRS Tech Note)
- Cernox resistor calibration report data plot
- Cernox resistor calibration data file
- Mathcad program notes
- Video: Superfluid Helium (Abridged version from BBC),
- Video: Full version of a 1963 film by Alfred Leitner at Michigan State Unversity.
