Design and Operating Characteristics of an Open Cycle Cooling System for Superconducting High Speed Electronics
A liquid helium cooling system for niobium based superconducting circuits was developed. It features delivery of cryogen and venting of waste gas through a coaxial transfer line assembly. The electronic circuits including their room temperature interfaces are located in a separable module. They are linked with the transfer line by electrical and cryogenic connectors. The cryogen flow is controlled via the supply dewar pressure. Expended cooling fluid is heated to ambient temperature and vented to atmosphere. A shutoff valve at the waste gas exhaust port allows for a rapid warmup of the circuits beyond their transition temperature. This feature is required for the untrapping of magnetic flux from the thin films of the circuits. A low thermal mass of the system components results in rapid cooldowns with times to 4.2K below a minute. Steady state helium consumption is approximately 0.7 L/h for single channel and 1 L/h for dual channel plug-in modules. A level sensor and a pressure transducer provide signals to electronic circuits for control of the system operation.
KeywordsLiquid Helium Josephson Junction Vent Valve Flow Control System Junction Voltage
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