Attractive performance of a Gifford–McMahon cryocooler by co-axial layout of regenerator materials

A novel filling method of regenerator materials, which we name a co-axial layout, is experimentally investigated. The 2nd stage regenerator of a Gifford–McMahon cryocooler was packed with 50% by volume of the co-axial layout (low temperature side) that consisted of 20% Gd2O2S and 30% HoCu2 spheres. The warm temperature side was packed with 50% lead spheres as a single layer. The experimental results show that the cooling power of co-axial layout is almost the same as that of a three-layer layout, 20% Gd2O2S, 30% HoCu2 and 50% lead, at temperatures between the ultimate low temperature (3.0 K) and 6 K. Moreover, at the temperatures above 10 K, the co-axial layout has 1.7–2.0 times the cooling power of the three-layer layout. Thus the co-axial layout produces a major improvement in cooling power. In this paper, the performance of five types of material assortments is discussed.

► A novel filling method of regenerator materials, a co-axial layout, is investigated.
► A feature of the co-axial layout is that a helium flow is divided into two areas.
► The co-axial layout makes it possible to combine the property of two materials.