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We have developed a lead-based regenerator material which is suitable for working temperatures below 20 K. This material can be used as a substitute for the state of the art non-magnetic materials used today within very low-temperature regenerators. This high efficient regenerator matrix combines technological advantages with the possibility to vary the thermodynamic and flow characteristics over a wide range, continuously. Hence, our self-made electroplated screen material is compared with standard regenerator materials (commercially available woven screens and packed spheres). We present the pressure drop and heat transfer characteristics of the new material for matrix porosities between 0.55 and 0.38 which corresponds to the porosities of screens and packed spheres. The design parameters and the influencing variables to optimise the regenerator performance will be discussed. The utility of the shop-made lead coated regenerator material is demonstrated in a coaxial two-staged pulse tube refrigerator wit...

The authors have undertaken basic research and prototype developments on various four valve pulse tube refrigerators (FVPTR) since several years. Systematic studies have been carried out to characterize the basics of the arising loss mechanisms of this type of pulse tube refrigerator with its active type of phase shifting. Recently, a single‐stage FVPTR in coaxial arrangement has been designed for maximum refrigeration power at cooling temperatures below 30 K limited by an available electrical input power of 6.2 kW. At present the single stage cooler provides a cooling capacity of 10 W or 20 W at working temperatures of 22 K or 27 K, respectively. Instead of lead spheres, lead coated screens have been applied in the coldest part of the regenerator in order to decrease the pressure drop. The improvement of the refrigerator overcomes the well known shortcoming of a refrigerator with a regenerator partially filled with lead spheres at working‐temperatures above 50 K. Numerical simulations of the thermodynamical process yield to continuative lead screen parameter studies. The results raise hope for achievable minimum temperatures down to 15 K. We report on the improved performance of the FVPTR due to the use of lead‐coated screens.