Development of superconducting for Large Helical Device

This paper reports on superconducting helical coils of the Large Helical Device (LHD) which requires the superconducting conductors with large current capacity from 20 kA to 30 kA and high current density of 55 A/mm2 at 8 T. NbTi superconductor with pool boiling is selected considering the large electromagnetic force and the complicated helical windings. Several conductors are designed aiming to study how the difference of the position of pure aluminum in the conductors affects the stability and the mechanical properties. Scale-down R and D conductors with the operational current from 7 kA to 10 kA were made on an experimental basis