Abstract A new class of magnetic regenerator materials for 4 K cryocoolers has been developed. A hexagonal gadolinium oxisulfide Gd2O2S=GO8 has been found to provide a very high volumetric heat capacity of more than 1 J/cm3K at 5.2 K. Polycrystal ceramic GOS particles have been fabricated with diameters between 0.35 mm and 0.45 mm. The achieved smooth surface on the spherical particles and a Vickers hardness of ∼900 make the material very suitable for use in regenerators. The measured data on the thermal and magnetic properties of the GOS also show excellent characteristics as a regenerator material; no change in heat capacity is observed when applying a magnetic field up to 1 T, and the high thermal conductivity of ∼0.05 W/cmK at 6 K is twice that of GAP. Magnetization of GOS at 1 T is about half that of HoCu2 between 2 K and 20 K. System-level cooling tests have been conducted with both GM-cycle and pulse tube cryocoolers where a portion of the HoCu2 in the 2nd regenerator was replaced with GOS. At a 50% volumetric ratio of GOS to HoCu2 the cooling power increased up to ∼25 % at 4.2 K. The cooling power did not drop above 4.5 K, where it significantly decreases when GAP is used. The new ceramic regenerator material GOS is expected to not only contribute to increased cooling performance at 4.2 K, but also to decreased fabrication cost.
A New Ceramic Magnetic Regenerator Material for 4 K Cryocoolers
Cryocoolers 12 ; 473-481
2003-01-01
9 pages
Article/Chapter (Book)
Electronic Resource
English
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