Magnetic regenerator material economizing method for 4K Gifford-McMahon cryocoolers using bakelite rod Free

Magnetic regenerator materials, such as $HoCu2$⁠, $Er3Ni$⁠, $Gd2O2S$⁠, and so on, are always needed to produce the cooling power at the temperature of 4.2 K using regenerative cryocoolers. The use of a large quantity of magnetic regenerator materials affects directly the fabrication cost of 4K cryocoolers. From this point of view, we introduce a magnetic regenerator material economizing method in this paper. An innovative regenerator structure was adopted for two-stage Gifford-McMahon (GM) cryocooler. The structure has a bakelite rod inserted in the co-axial layout of the 2nd stage regenerator in which $HoCu2$ spheres are filled. The cold temperature side of the 2nd stage regenerator is occupied with 50% by volume of the bakelite rod and $HoCu2$ spheres, and the warm side is packed with lead (Pb) spheres as a single layer. The bakelite rod is a dummy volume. Two types of conventional GM cryocoolers with power consumption of 1.3 and 7.3 kW, respectively, are tested. The experimental results show that the filling volume of $HoCu2$ spheres of 1.3 and 7.3 kW models is able to economize by 20% and 10% without deterioration of the cooling power at 4.2 K, respectively. In this paper, the regenerator structure and detailed experimental results will be presented.