Abstract Advances in regenerator reliability, as well as material cost reduction, can be obtained by optimizing the geometry of the regenerator material. This ongoing development effort for <10K Gifford-McMahon (G-M) refrigerators utilizes coiled ribbons of Neodymium (Nd) instead of the typical spheroidal powder. The ribbons, which have small ridges on one face, are coiled to form flat pancakes. The height of the ridge in relation to the thickness of the tape determines the void volume. These flat coils are then stacked to form a cylinder and packed into the second stage of a G-M refrigerator, in the place of the Nd spheres. This paper describes the fabrication process used to create ribbons from the Nd rare-earth material. Although easier to fabricate than intermetallic regenerator materials, Nd work-hardens and oxidizes rapidly. Modifications were made to conventional extrusion, drawing and rolling processes to overcome these difficulties. The production process developed has much greater yields (>80%) than current Nd powder atomization techniques, which yields only 15% to 30%. Test results show that the amount of void volume, and therefore the pressure drop, can easily be controlled and optimized by varying the ribbon geometry. Whereas the void volume of packed Nd powder is normally roughly 35%, ribbon geometries with void volumes of 15% and 20%, were manufactured and tested. Current efforts are described to further improve the geometry and increase cryogenic performance well beyond that of spherical powder materials.
Advances in Neodymium Ribbon Regenerator Materials
Cryocoolers 10 ; 621-628
2002-01-01
8 pages
Article/Chapter (Book)
Electronic Resource
English
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