Overview of the Large Helical Device project

The Large Helical Device (LHD) has successfully started running plasma conf inement experiments after a long construction period of eight years. During the construction and machine commissioning phases, a variety of milestones were attained in fusion engineering which successfully led to the first op eration, and the first plasma vr;as ignited on 31 March 1998. Two experimen tal campaigns were carried out in 1998. In the first campaign, the magnetic flux mapping clearly demonstrated a nested structure of magnetic surfaces. The first plasma experiments were conducted with second harmonic 84 and 82 .6 GHz ECH at a heating power input of 0.35 MW. The magnetic field was set at 1.5 T in these campaigns so as to accumulate operational experience with the superconducting coils. In the second campaign, auxiliary heating with NBI at 3 MW has been carried out. Averaged electron densities of up to 6 x 10(19) m(-3), central temperatures ranging from 1.4 to 1.5 keV and stored e nergies of up to 0.22 MJ have been attained despite the fact that the impur ity level has not yet been minimized. The obtained scaling of energy confin ement time has been found to be consistent with the ISS95 scaling law with some enhancement.