Preliminary Design of Cooling System for a PrFeB-based Cryogenic Permanent Magnet Undulator Prototype at IHEP

A circulation cooling system is under progress for a 2m-long PrFeB-based cryogenic permanent magnet undulator (CPMU) prototype at IHEP. Sub-cooled liquid nitrogen flows through each in-vacuum girder back and forth once. Refrigerant channels for both girders are parallel connected in vacuum chamber. Numerical simulation shows that the cooling system is able to cool down magnet array from 300 K to 83 K. Meanwhile, phase error increases about 0.1 degree.