Performance of the LHD magnet system

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 8-yr Phase I project for LHD were completed on March 31, 1998 as initially planned. The second experimental campaign was conducted by additional heating using two neutral beam injection (NBI) devices. The third campaign started in June 1999 and was completed in January 2000. The fourth campaign started in August 2000 and was completed in March 2001. The fifth campaign is carried on since August 2001. Many plasma heating tests up to a plasma field of 2.90 T were carried out. Major test results on the SC magnet system for LHD are as follows: 1) The LHD cryogenic system succeeded in 17 900-h operation as of September 21, 2001 and proved its high reliability. 2) A central field of 2.993 T at a radius of 3.50 m was achieved at a helical coil inner block (H-I) current of 10.97 kA, a helical coil middle block (H-M) current of 11.87 kA and a helical coil outer block (H-O) current of 12.07 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.