Axial Component of Mutual Friction in Uniformly Rotating Liquid Helium

For helium II in uniform rotation, the component of mutual friction along the rotational axis Bz has been studied. The attenuation of second sound transverse to the axis of rotation (characterized by the parameter B) has been compared with the attenuation in the direction of the axis (measured by Bz). It is shown: that B/Bz > 500 over a large range of temperature and frequency; that Bz is not very reproducible; that Bz is dependent on the second sound amplitude; and that Bz is not linear in Ω, the rate of rotation. Within the temperature and frequency range covered by Hall and Vinen the present data on B agree with the results of these authors. Near the λ point, B increases rapidly. The anomalous dependence of B on Ω near 2.0°K as reported by Hall and Vinen is not observed. Some preliminary measurements of the parameter B′ are mentioned.