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Development of a 1 W, 10 K Reverse Brayton Cycle Cryocooler--Doty Scientific, Inc., 700 Clemson Road, Columbia, SC 29229-4339; 803-788-6497
Dr. F. David Doty, Principal Investigator
Mr. George Entzminger, Business Official
DOE Grant No. DE-FG02-98ER82565
Amount: $749,900
The security of special nuclear material requires the capability for spectroscopically resolved three-dimensional high-resolution imaging. The high sensitivity detectors (for long-wave-IR, magnetism, X-ray, and mid-IR) needed for this capability require continuous cryogenic cooling (to 8-30 K) via reliable, ultra-low-vibration, miniature (0.5-5 W), fieldable cryocoolers. However, severe vibration of available cryocoolers seriously degrades sensitivity and resolution. This project will develop Reverse Brayton Cycle (RBC) cryocoolers with turbo-expanders and turbo-compressors that have negligible vibration and potentially high efficiency. The cryocooler, based on a unique expander design, utilizes a Nd-B-Fe generator core and dual micro-turbines with 4 mm gas bearings (made of silicon-nitride). This design permits the RBC to be scaled down by at least two orders of magnitude compared to existing RBC cryocoolers. Phase I demonstrated a two-orders-of-magnitude reduction in vibration and proved the technical feasibility of the following critical components: (1) micro-cryo-generators that are two orders of magnitude smaller than prior technology; (2) micro-turbo-expanders scalable down to 0.1 g/s; and (3) compact, high-effectiveness recuperators. The Phase II effort will optimize all the required components for the RBC cryocooler and deliver a reliable, ultra-low-vibration, fieldable, 10 K refrigerator to cool high sensitivity detectors and/or other apparatus to cryogenic temperatures.
Commercial Applications and Other Benefits as described by the awardee: The current market for cryocoolers in this size range is several thousand units per year for (1) high sensitivity radiation detectors and imagers, (2) targeting devices, (3) MRI and NMR superconducting magnets, and (4) NMR cryoprobes for biomolecular structure determinations. Additional markets may develop in the next century for refrigeration of liquid hydrogen fuel and for cryogenic microprocessors.