Upgrading and Experiment of the 6T Superconducting Wiggler Magnets' Cryogenic System

In 1998, the Hefei National Synchrotron Radiation Laboratory completed the 6 T superconducting Wiggler magnets system. The consumption of liquid helium increases year by year during long operations. In order to upgrade the cryogenic system and remove the use of liquid helium, GM cryocoolers are introduced as the cooling source. The liquid nitrogen and radiation-proof cold screen of the original cryogenic system were removed, and the original copper current leads were replaced with high-temperature superconducting current leads. The total heat load of the cryogenic system is 2.33 W at 4.2 K and 108 W at 60 K. Three GM cryocoolers are selected as the cryogenic source. They can provide 3.75 W at 4.2 K and 210 W at 60 K. In the absence of an external precooling source, the final cryogenic system was successfully cooled and produced liquid helium at a liquefaction rate of 12 L/day at 1.1 bar (inflationary pressure) and had an excess cooling capacity of more than 1.05 W at 4.1 K.