Abstract: A power operated contact apparatus extends and retracts one or more electrical leads into and out of a cryostat for making and breaking, at a cryogenic temperature, electrical contacts with a superconductive circuit. A pair of rigid elongated leads extend into a cold space of the cryostat which is at or near a cryogenic temperature. A connector is fixed at the inner end of each lead for making electrical contact in the cold space with a mating connector of the superconductive circuit. A guide journals each lead for axial movement and seals against the leading using an elastomeric O-ring coated with a lubricious polymer. A foundation is attached and sealed to the cryostat and to the guide means so that the connector on the inner end of the lead is extendable into making electrical contact with the connector of the superconductive circuit in the cold space.

Abstract: An improvement has been made to a cryogenic liquid level detection system of the type wherein a small electrical current is passed through a filament of superconducting material to generate a voltage proportional to the length of the filament above the liquid level. This improvement involves automatically interrupting the current flow immediately upon the growth of the normal resistance state of the filament above the liquid down to the liquid surface. Normally current flow is then reinitiated after a preset time interval. In this manner there is a minimum energy input to the liquid from the current and thus evaporative losses of the liquid are minimized.