Long-pulse plasma discharge on the Large Helical Device

A long-pulse plasma discharge of more than 30 min duration was achieved on the Large Helical Device (LHD). A plasma of n e = 0.8 × 10 19 m −3 and T i0 = 2.0 keV was sustained with P ICH = 0.52 MW, P ECH = 0.1 MW and averaged P NBI = 0.067 MW. The total injected heating energy was 1.3 GJ. One of the keys to the success of the experiment was a dispersion of the local plasma heat load to divertors, accomplished by sweeping the magnetic axis inward and outward. Causes limiting the long pulse plasma discharge are discussed. An ion impurity penetration limited further long-pulse discharge in the 8th experimental campaign (2004).