Development of Superconductor Joint for Helical Coils

A new superconductor joint, named the “Pipe Pressing Method”, has been developed and the characteristic of the joint was investigated considering its application to Heliotron F and G^(1)(2)(3) which are being designed as the next reactor models of Heliotron E ⁽¹⁾ at Kyoto University. We have observed that this joint is almost superconducting. The critical current density of the joint at 6 Tesla is 310 A/mm² which is about one third that of the original superconductor. The voltage drop across the joints is less than 2µV. Utilizing this method, the total cooling power for the superconducting coil system for Heliotron G reactor⁽²⁾ is estimated to increase at most several percent.