Cooling Design for the Magnetic Structure of SHINE Superconducting Undulator

Forty planar superconducting undulators (SCUs) of 4 m length will be used in Shanghai High Repetition rate XFEL and Extreme Light (SHINE) facility. As the longest SCU in developing of the worldwide, they could generate photon in energy range of 10-25 keV. NbTi/Cu wires with the diameter 0.6 mm and the ratio of Cu to NbTi 0.9 have been chosen as the fundamental element of superconducting coils. Coils temperature must be below 5 K when operating current reaches 400 A. Meanwhile, the magnetic gap need to be less than 5 mm to obtain the peak field of 1.58 T. Therefore, beam chamber installation is infeasible in such a small gap. Two parallel copper foils close to the surface of magnetic poles have been designed to shield beam heat load. Furthermore, four liquid Helium tubes located symmetrically around magnetic structure have been designed to cool the copper foils used as beam channel. There is no cryocooler on the SCU because liquid Helium is provided by the cryogenic plant of SHINE.