Reliability Engineering of Cryocooler-Based HTS Magnets for FCC-ee

The objective of this study is to demonstrate the feasibility of reliable accelerator operation using a main ring based on a large number of superconducting magnets with individual cooling systems. This can be achieved by employing some redundancy within the cooling modules. Our specific targeted application concerns the possibility of using 2900 superconducting short straight sections as part of the FCC-ee main ring. These magnets are envisioned to be made from high temperature superconductor (ReBCO) operating at roughly 40 K. The high-reliability configurations consist of multiple single-stage Gifford-McMahon coldheads per magnet, allowing for continuous cooling even in the event of a failure in one of the coldheads. The main drawback of the redundancy is the extra heat load through the off-state cooler necks. Based on our calculations, the estimated reliability and availability of the total magnet ring's cryogenic cooling systems over a 1-year period are at least 0.994 and 0.999, respectively.