1. Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey, U.S.A
2. University of California at Davis, California, U.S.A
3. FOM-Institute for Plasma Physics Rijnhuizen, Association EURATOM-FOM, P.O. Box 1207, 3430 BE Nieuwegein, The Netherlands
4. University of Colorado at Boulder, Colorado, U.S.A.
5. Forschungszentrum Jülich GmbH, Institut für Plasmaphysik, Association EURATOM-FZJ, D-52425 Jülich, Germany