Recirculating 1-K-Pot for Pulse-Tube Cryostats

A paper describes a 1-K-pot that works with a commercial pulse tube cooler for astrophysics instrumentation testbeds that require temperatures <1.7 K. Pumped liquid helium-4 cryostats were commonly used to achieve this temperature. However, liquid helium-4 cryostats are being replaced with cryostats using pulse tube coolers.

The closed-cycle 1K-pot system for the pulse tube cooler requires a heat exchanger on the pulse tube, a flow restriction, pump-out line, and pump system that recirculates helium-4. The heat exchanger precools and liquefies helium-4 gas at the 2.5 to 3.5 K pulse tube cold head.

This closed-cycle 1-K-pot system was designed to work with commercially available laboratory pulse tube coolers. It was built using common laboratory equipment such as stainless steel tubing and a mechanical pump. The system is self-contained and requires only common wall power to operate. The lift of 15 mW at 1.1 K and base temperature of 0.97 K are provided continuously. The system can be scaled to higher heat lifts of ≈30 to 50 mW if desired.

Ground-based telescopes could use this innovation to improve the efficiency of existing cryogenic systems or as a basis of new systems.

This work was done by Christopher G. Paine, Bret J. Naylor, and Thomas Prouve of Caltech for NASA’s Jet Propulsion Laboratory. NPO-48355

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