Electrostatic Manipulation of Level of Bulk Liquid for Studies of Saturated Superfluid 3He Films

Abstract

In studies of saturated superfluid helium films, the level of bulk liquid is an important parameter in determining the thickness of the film. To change the level at low temperatures, a complicated system with a bellows and an extra fill line is usually needed. In this paper, we report a simple device that can be used to change the level using an electrostatic force. This level controller consists of a stack of 60 silver plates of 0.1 mm thickness, separated from each other by a 0.1 mm gap. The application of a dc voltage V to every other plate pulls the dielectric liquid 3He into the gaps, resulting in the drop of the bulk level. The change in level is in agreement with that expected by the balance between the electrostatic force and gravity, and the decrease is as large as 0.27 mm at V=200 V. The level controller is also used to detect the superfluid transition of bulk liquid 3He through the sudden reduction of the response time after V is varied.