[1] CIEMAT, EURATOM Assoc, E-28040 Madrid, Spain
[2] Jet Joint Undertaking, Abingdon OX14 3EA, Oxon, England
[3] Max Planck Inst Plasmaphys, EFDA CSU Garching, D-85748 Garching, Germany
[4] Max Planck Inst Plasma Phys, EURATOM Assoc, D-85740 Garching, Germany
[5] UKAEA Euratom Fus Assoc, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England