Design, development and testing of cryogen free 1K refrigeration system

A 1Kelvin refrigeration system using closed cycle cryocooler is developed for testing of components for quantum computers. This system is used for extensive characterization of Superconducting RF cavity for SC Qubits. In this system, high purity helium-4 gas is liquefied using closed cycle cryocoolers and is evacuated to achieve low temperature. The helium gas is passed though charcoal trap and is cooled to 40K using heat exchangers attached to first stage of cryocooler. The precooled helium gas is liquefied using heat exchangers attached to the second stage of cryocooler (4K). The liquefied helium is passed through a Joule Thomson (JT) Impedance valve into a cylindrical vessel, which is evacuated to decrease the vapor pressure and achieve low temperature. The heat exchangers are designed to meet the thermodynamic requirements to precool and condense the helium gas before evacuation. Proper thermal design and development techniques are employed to reduce conduction, radiative heat load and thermal contact resistance between the heat exchanger and its support plates which are connected to the cryocoolers flanges. The developed system is integrated and tested for its performance. This system has achieved a temperature of 1.5K (-271.65◦C) with helium gas flow rate of 200 SCCM.