Positive Ions in Liquid Helium II. The Critical Velocity for Creation of Vortex Rings

Abstract

In this paper we report the results of experiments from which we have obtained the value of the critical velocity for quantized-vortex-ring creation by positive ions in liquid helium II. We have investigated the temperature range between 1.0 and 1.5\ifmmode^\circ\else\textdegree\fi{}K. The critical velocity depends on temperature above 1.1\ifmmode^\circ\else\textdegree\fi{}K.