Design and development of a cryogenic J-T valve for a 2 K cryostat with a single cryocooler

Abstract

A cryogenic Joule-Thomson (J-T) valve for a 2 K cryostat cooled with a G-M cryocooler has been developed to continuously supply superfluid helium. Saturated liquid helium flowing through the valve transitions to superfluid helium below 2 K because of the J-T effect. The heat leak, sealing performance and the J-T effect of the valve were tested experimentally and analyzed. To reduce heat leak in the 2 K range, two thermal anchors were installed in the first and second cooling stages, respectively, resulting in 89.93% reduction of useful work loss. A unique sealing structure was developed for the J-T valve and was tested at both room temperature and liquid nitrogen temperature, yielding leak rates of 3 × 10-9 Pa· m3/s and 3 × 10-4 Pa· m3/s, respectively. The corresponding valve needle and seat structure were designed based on the flow resistance equation. The J-T effect of the valve in 2 K cryostat was tested at various valve openings. The cryostat can operate at 1.64 K with no load and provide 0.143 W cooling power at 2 K.