Control System for Temperatures and Liquid Level between 4.2° and 1°K
An earlier publication  describes a continuous open-cycle cooling process for liquid-helium cryostats which permits one to maintain a constant liquid level in the cryostat for any length of time for helium-I at temperature levels between the normal boiling point and the λ-point. In this process, the cryostat is refilled by means of a vent-gas cooled transfer tube which has an expansion valve at the exit surrounded by sintered metal. The expansion valve is regulated by means of an electric liquid-level controller. A control valve In the vent-gas pipe connected to a vacuum pump Is operated by a pressure control. The liquid level remains essentially stable even If the expansion valve Is placed only 1 cm above it. This process makes it possible to refill even very small volumes with helium. A temperature constancy of ΔT/T = 10-3 is also achieved, with this process.
KeywordsExpansion Volume Liquid Level Breakthrough Point Aluminum Silicate Superfluid Helium
Unable to display preview. Download preview PDF.