Achieved capability of the superconducting magnet system for the Large Helical Device

The Large Helical Device (LHD) is a plasma physics experimental device with a magnetic stored energy of 960 MJ, consisting of two superconducting (SC) helical coils and six SC poloidal coils. The trial operation and the first plasma discharge of the Phase I project for LHD were completed on 31 March 1998 as initially planned. The second experimental campaign was conducted with additional heating using two NBI devices. The third campaign started in June 1999 and was completed in January 2000. Many plasma heating tests with a plasma field of up to 2.90 T were carried out. Major test results on the SC magnet system for LHD are as follows: (1) The LHD cryogenic system was successfully operated for 13 400 h and proved its high reliability. (2) A central field of 2.91 T at a radius of 3.60 m was achieved at an inner helical coil current of 11.08 kA, a middle helical coil current of 11.83 kA and an outer helical coil current of 12.02 kA. (3) All six poloidal coils were excited stably. (4) Nine flexible SC bus lines with a total length of 497 m were operated stably and safely.