Initial Cooldown Characteristic of Conduction-Cooled High Field Magnet System

Cooldown time is one of the major factors in the conduction-cooled superconducting magnet system. Cooldown time means a time cooling a superconducting magnet from room temperature to cryogenic temperature within a stipulated amount of time. The estimation of cooldown time seeks the elapsed time to cool the superconducting magnet by cryocooler during initial cooldown process. This procedure includes the modeling of properties of low temperature superconductor, the dimensions of superconducting magnet, the cryogenic loads, the thermal link between magnet and cryocooler, and the available refrigerating capacity of cryocooler. This method is applied to the conduction-cooled superconducting magnet system developed by ourselves for accuracy confirmation. The effects of magnetic field, size of magnet and thermal link on the initial cooldown are also discussed.