Development of tin-plated regenerator material

Abstract

To improve the efficiency of a cryocooler, it is vital to improve the regenerator. In general, the heat capacity of materials decreases as temperature decreases. Thus, when temperature is below 50 K, lead spheres are often used as a regenerator material. However, the pressure drop through a sphere regenerator is larger than that through a screen regenerator. To overcome this dilemma, a new, low pressure loss tin-plated screen is proposed. A comparison test was performed with a two-stage GM cryocooler by replacing part of the first stage regenerator material, bronze screens with tin-plated screens. Compared to a regenerator filled with bronze screens, the cooling capacity of the first stage increased by about 14% at 40 K and 90% at 30 K with such tin-plated screens. The ratio of the wire diameter before and after the deposition was also optimized. An optimum cooling capacity of 53.5 W at 40 K was obtained at a diameter ratio of about 1.4. The detailed experimental results are reported in this paper.