Second Sound Attenuation in Rotating Helium II

Abstract

An experiment is described wherein liquid helium II is rotated in an annulus between a metal cylinder which rotates at constant speed and a concentric cylindrical cavity at rest. Second sound pulses, propagated parallel to the cylindrical axis and through a substantially uniform velocity field, are found to suffer an extra attenuation due to the motion of the fluid. If we define $\ensuremath{\sigma}$ as the ratio of the received thermal pulse heights (fluid in motion versus fluid at rest), then for angular velocities of the cylinder $\ensuremath{\omega}$ and second sound path lengths $l$ it appears that $\ensuremath{\sigma}={e}^{\ensuremath{-}\ensuremath{\beta}\ensuremath{\omega}l}$. The coefficient $\ensuremath{\beta}$ decreases somewhat with rising temperature in the range from about 1.2 to 2.0\ifmmode^\circ\else\textdegree\fi{}K, having a value of (8\ifmmode\pm\else\textpm\fi{}0.8)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}3}$ ${\mathrm{rev}}^{\ensuremath{-}1}$ ${\mathrm{cm}}^{\ensuremath{-}1}$ sec at 1.39\ifmmode^\circ\else\textdegree\fi{}K. The effect is discussed in the light of present knowledge concerning the nature of helium II.