Review of initial experimental results of the PSI studies in the large helical device

The large helical device (LHD) is the largest heliotron type superconductin g device. Its operation was started on 31 March 1998. Three experimental ca mpaigns have been completed until the end of 1999. Wall conditioning mainly by cleaning discharges using ECRF or glow discharges worked well even with out high temperature baking, The plasma production with ECRH and auxiliary heating with NBI and/or ICRF in the LHD configuration equipped with open he lical divertor were well performed. The divertor material was SS316L in the first and second campaigns, and was replaced by the graphite in the third campaign. The influences of the different divertor materials were investiga ted. Our understanding of the edge and the divertor plasma has progressed. Long-pulse discharges 80 and 68 s heated by NBI (0.5 MW) or ICRF (0.9 MW) h ave been achieved, respectively. No severe limitation of the duration has a ppeared. (C) 2001 Elsevier Science B.V. All rights reserved.