A Study on Cooling System of HTS Quadrupole Magnets for Heavy Ion Accelerator

Quadrupole magnets located at the front end of an in-flight fragment (IF) separator in a heavy ion accelerator have large heat loads due to neutron radiation. Thus, high-temperature superconducting (HTS) magnets are used instead of low-temperature superconducting (LTS) magnets because of their high cooling efficiency and thermal stability. The cooling system of the HTS magnet uses circulation of cold helium gas. The circulating helium gas is provided from the distribution box, where helium gas lines are divided into 7 pairs of small helium lines corresponding to 7 HTS magnets. To cool down the 7 HTS magnets with different heat loads, the mass flow rate of each magnet should be individually controlled by monitoring the temperature of the magnets. This paper describes the cooling system for the 7 HTS magnets considering the heat load of each magnet and the thermohydraulic characteristics of the cooling system, including a heat exchanger, a cryogenic blower, control valves, etc. The helium mass flow rates for each magnet and the temperature at the outlet of the magnet are determined so that the magnets operate below 45 K. The optimal helium mass flow rates for each magnet were determined by analyzing the correlation between the magnet outlet temperature and flow rate.