Design of Active Magnetic Regenerative Stage Interfacing to a G-M Cryocooler
An active magnetic regenerative (AMR) stage producing sub-4K cooling has been designed. Performance modeling predicts a cooling power of 1.6 W at 3.5 K and 3 W at 4.5 K. The stage rejects heat to a conventional Gifford-McMahon (G-M) cryocooler at about 10 K.
Use of a ferromagnetic erbium-nickel alloy with the AMR configuration allows use of a lower field (3 T) than that required by a magnetic Carnot cycle. Two AMR beds are reciprocated into a fixed Nb3Sn magnet operated in persistent mode. The magnet is conductively cooled using a G-M cryocooler. The heat transfer fluid used in the AMR is sub-atmospheric helium gas moved by a bellows displacer. The moving AMR beds are linked by bellows to two fixed parallel plate hot heat exchangers and one fixed cold heat exchanger. The design does not need liquid cryogens for operation, and has no sliding seals in the helium flow circuit.
KeywordsHeat Exchanger Heat Transfer Fluid Vacuum Vessel Helium Pressure Pneumatic Cylinder
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