Graphene-Cu Hybrid Foil Thermal Straps for Conduction Cooling of SRF systems

Conductively linking compact accelerator systems with advanced cryocoolers though high-performance thermal straps would eliminate the requirements for liquid cryogens, and thus facilitate rapid attainment of operational temperatures. However, the sluggish conduction cooling rate of traditional thermal straps made from copper, aluminum, or graphite hinders the practical applications of thermal straps to compact accelerators and superconducting radio frequency technologies. If the thermal and mechanical properties of thermal straps could be improved, this would effectively balance the device heat dissipation with the cryocooler capacity, and reduce the conduction cooling time, enabling faster operation. The proposed project aims to develop a scalable manufacturing approach for producing graphene-copper hybrid foil based thermal straps for connecting superconducting radio frequency cavities or other related devices with cryocooler to reduce cooldown time. The proposed program utilizes the intrinsic physiochemical, thermal and mechanical properties of graphene and copper matrix, combined with advanced electro-codeposition techniques for hybrid strap fabrication. The proposed technology can tailor graphene-copper hybrid properties as needed for tuned operational performance, making the hybrid material an ideal thermal strap for fast conduction cooling processes. Furthermore, the process is inherently low- cost, robust and scalable, making it suitable for industrialization. Phase I will build an electro-codeposition apparatus and investigate the parameters of a pulse/pulse reverse electro-codeposition process for fabricating graphene-copper hybrid foils for thermal straps. The thermal and mechanical properties of the copper-graphene hybrid foils will be evaluated through characterization of thermal conductivity, thermal cycling, and mechanical stiffness. A preliminary economic/scale-up analysis will provide high-level metrics for the potential industrial-scale viability of the proposed process. Other than the applications for compact accelerator systems for high energy physics experiments, the copper-graphene hybrid material technology will be of interest to agencies with advanced thermal management needs via a conduction cooling process, including NASA and Air Force. Furthermore, the proposed technology is anticipated to attract interest from the very large market for medical electronics, which mostly use conduction cooling technology for heat transfer.