Home > Proceedings of the 14th International Cryocooler Conference > Koettig

Abstract

Based on our extensive experience with the development of single-stage pulse tube refrigerators in a coaxial configuration we have designed a new type of two-stage pulse tube refrigerator. Our experimental results concerning the intermediate thermal contact between the pulse tube and the regenerator have allowed us to combine the two-stage arrangement with the coaxial design. We arranged two needle valves at the hot end of each pulse tube to create a valve-controlled active type of phase shifting. The second stage regenerator matrix is composed of our latest self-made lead-coated screen material. To make this material, stainless steel screens with an initial wire diameter of 36 μm (158 mesh) were electroplated to a resulting wire diameter between 105 μm and 125 μm. Hence, this wide range of lead coated wire diameters at constant mesh number made it possible to achieve an inhomogeneous regenerator with porosities from 0.43 to 0.37 into the second stage. The resulting refrigerator reached a no load temperature of 6.5 K and provides a cooling capacity of 2 W at 9.5 K; this is limited by the 6.2 kW electrical input power of our Leybold RW 6000 compressor. The design parameters and the influencing variables to optimize the cooling performance are discussed.