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 i n June 1999 and was completed in January 2000. Many plasma heating tests wi th a plasma field of up to 2.90 T were carried out. Major test results on t he SC magnet system for LHD are as follows: (1) The LHD cryogenic system wa s 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 hel ical coil current of 11.08 kA, a middle helical coil current of 11.83 kA an d an outer helical coil current of 12.02 kA. (3) All six poloidal coils wer e excited stably. (4) Nine flexible SC bus lines with a total length of 497 m were operated stably and safely.