Theoretical study on pre-cooling of a cold mass using a 4 K Pulse-Tube cryocooler

The 4 K pulse tube cryocooler is a key part of a Dry Dilution Refrigerator, designed to reach temperatures of around 40 K and 4 K on the 1^st and 2^nd stage flanges, respectively. At VECC, a system is being developed to explore helium condensation under different pressures in a high-impedance line, with the goal of achieving low temperatures close to 1 K. Before the system can operate, the temperature of the test cold mass needs to drop below 20 K in a reasonable amount of time. Since the main system has high flow impedance, a separate pre-cooling loop has been introduced. This closed-loop system, thermally anchored to the cryocooler’s two stages, helps cooldown the cold mass to below 20 K. This paper describes the design and analysis for fabricating a pre-cooling system using a PT cryocooler.