1. Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08540-451, USA
2. Plasma Science and Fusion Center, MIT, Cambridge, Massachusetts 02139, USA
3. Atominstitut, Technische Universität Wien, Stadionallee 2, 1020 Vienna, Austria
4. ITER Organization, Route de Vinon sur Verdon, 13067 St. Paul Lez Durance, France
5. Culham Centre for Fusion Energy, Culham Science Centre, Abingdon OX14 3DB, United Kingdom