Thermal analysis and preliminary cooldown performance of the SCU cryostat

The SCU cryostat, featuring two 1.5-meter-long Nb-Ti superconducting undulators (SCUs), is currently being built for the Advanced Photon Source Upgrade. The final design, along with the thermal and mechanical models of this cryocooler-cooled, liquid helium-based cryostat, has been completed. The cryostat has been fabricated, and preliminary cool-down tests were conducted both with and without the two 1.5-meter-long Nb-Ti SCUs. This paper presents a comparison between the measured and calculated thermal performance of the cryostat.