Viscosity Measurements on Liquid ⁴He by Means of a Torsional Oscillator

Abstract

The viscosity of liquid ⁴He has been measured by means of a high-Q torsional oscillator at temperatures between 1.5K and 2.7K under saturated vapor pressure. The viscosity data derived from the resonant frequency difference between the empty cell and the cell filled with liquid ⁴He show satisfactory agreement with the results obtained by Welber. When the velocity of cell-wall exceeded the critical velocity below the superfluid transition temperature, the decrease of the resonant frequency caused by the growth of the quantized-vortex was observed. In the case of a cell with rough wall, the critical velocity was low compared with a cell with smooth wall. The rate of the growth of vortex line length also depends on the wall roughness.