An Overview of the Large Helical Device Project

"AN OVERVIEW OF THE LARGE HELICAL DEVICE PROJECT. The Large Helical Device (LHD) has successfully started running plasma confinement experiments after a long construction period of eight years. During the construction and machine commissioning phases, a variety of milestones have been attained in fusion engineering, which successflly led to the first operation, and the first plasma was ignited on March 31, 1998. Two experimental campaigns are planned 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-GHz and 82.6-GHz ECH at a heating power input of 0.35 MW. The magnetic field was set at 1.5 T in the first year so as to accumulate operational experience of the superconducting coils. In the second campaign, auxiliary heating with NBI at 3 MW has been carried out. The averaged electron densities up to 6x 10^19 m^-3 , central temperatures ranging 1.4 to 1.5 keV and stored energies up to 220 kJ have been attained despite the fact that impurity level is not yet minimized. The obtained scaling of energy confinement time has been found to be consistent with the ISS95 scaling law with some enhancement.