1997 Volume 32 Issue 11 Pages 573-579
Poloidal coils for the Large Helical Device (LHD) were fabricated and finished in September 1996. The poloidal coil system consists of three pairs of circular solenoids: inner vertical (IV), inner shaping (IS) and outer vertical (OV) coils which have a center diameter of 11.1m. Conductors are of the NbTi cable-in-conduit type and cooled with supercritical helium. The conductors were designed to ensure high stability and safety. In addition, the conductors were strictly inspected during fabrication. A coil consists of eight double-pancake coils. To minimize the error magnetic field, the following three items were considered. First, the shapes and sizes of the feeder, layer transitions and conductor joints were optimized. Second, the coils were made to a tolerances of 2mm. The tolerance corresponds to an extreme accuracy of about 5×10-4 for the diameter. Lastly, a compact superconducting joint was applied for the electric joints between pancakes.
