Ions in He II at 1 degrees K. I. Velocity discontinuities

Abstract

In a study of the mobility of ions in liquid He II in the temperature range 0.89 degrees K to 1.0 degrees K, the existence of the sharp periodic velocity discontinuities, first detected by Careri, was confirmed. The discontinuities were found to occur at integral values of a critical drift velocity vc+=5.21+or-0.08 m s-1 for positive ions, and vc-=2.12+or-0.16 m s-1 for negative ions. Velocities were measured by a time-of-flight method, and at low values of the grid- source field, the previously undetected first discontinuity of the negative ions was found. Measurements were made of the magnitude Delta mu and shape of the first three discontinuities. The constant Delta mu values found for successive discontinuities and the observed lack of dependence of Delta mu on the grid-collector separation are is disagreement with the predictions of the vortex ring creation theory of Huang and Olinto.