Cooling Conditions Analysis of the Superconducting Outsert in the Series Connected Hybrid Magnet System

The cooling system design for the superconducting outsert of a 36 T Series-Connected Hybrid (SCH) magnet being developed at the NHMFL is discussed and analyzed. The outsert will be wound with a superconducting cable-in-conduit conductor (CICC) that uses a cable of multi-filamentary Nb₃Sn/Cu strands inside a high-strength alloy jacket that confines slowly flowing supercritical helium (under 3-3.5 atm pressure at 4.5 K) in direct contact with the cable strands. The cooling design option with the highest flow to all the winding layers is selected (each layer has an inlet and outlet), aiming to sustain a wide range of duty cycles required by diverse science experiments, conducted with this magnet. Typically, many experiments will need multiple cycles (charging/discharging) with short, albeit variable, waiting time before each one. The charging cycles would have ramp rates of about 30 A/s to relatively high ramp rates, up to 500-600 A/s. The different ramp rate characteristics will result in different patterns of deposition and evacuation of heat due to AC losses in the outsert windings. All of these cases are carefully analyzed and discussed.