Thermal and Mechanical Design of a HTS Quadrupole Magnet of In-Flight Fragment Separator for Rare Isotope Science Project (RISP)

An in-flight fragment (IF) system is used to produce and investigate an isotope beam of interest from heavy-ion accelerators, and it is composed of prestages and main stages. A quadrupole magnet of an IF preseparator is located in a high-radiation region, and the neutron radiation heat load is much larger than that of common superconducting magnets. Considering the efficiency of a cooling system, high-temperature superconducting (HTS) magnets are preferred to low-temperature superconducting magnets. To remove the large radiation heat load, the circulation of cold helium gas is used instead of conduction cooling. Pressurized helium gas circulates in cooling channels, and the optimized design of a cooling structure is required. Moreover, large Lorentz force is generated in the coil, and an appropriate supporting structure should be designed within the allowable conduction heat loss through the supporting structure. This paper describes the thermal and mechanical design of the REBCO HTS quadrupole magnet. Structural design is carried out considering the Lorentz force of the HTS magnet. Thermal analysis is also performed to estimate the heat loss using the designed structure. Finally, the design of a cooling system is carried out to keep the magnet temperature under 40 K against the estimated heat loss.