[1] Max Planck Inst Plasma Phys, IPP Euratom Assoc, D-85748 Garching, Germany
[2] Assoc Euratom ENEA Fus, Consorzio RFX, I-35127 Padua, Italy
[3] Ecole Polytech Fed Lausanne, Assoc Euratom Confederat Suisse, Ctr Rech Phys Plasmas, CH-1015 Lausanne, Switzerland
[4] CEA, Assoc Euratom, F-13108 St Paul Les Durance, France
[5] UKAEA, Abingdon OX14 3DB, Oxon, England
[6] CNR, Assoc Euratom ENEA, Ist Fis Plasma, I-20125 Milan, Italy
[7] Riso Natl Lab, Assoc Euratom Riso, DK-4000 Roskilde, Denmark