[1] Royal Inst Technol KTH, Assoc EURATOM VR, Div Fus Plasma Phys, Stockholm, Sweden
[2] Uppsala Univ, Assoc EURATOM VR, Tandem Lab, S-75105 Uppsala, Sweden
[3] Univ Helsinki, Dept Phys, Assoc EURATOM TEKES, Helsinki 00560, Finland
[4] Aalto Univ, Assoc EURATOM TEKES, Aalto 00076, Finland
[5] VTT, Assoc EURATOM TEKES, Espoo 02044, Finland
[6] Max Planck Inst Phys & Astrophys, EURATOM Assoc, D-85748 Garching, Germany
[7] Culham Sci Ctr, EURATOM CCFE Fus Assoc, Abingdon OX14 3DB, Oxon, England
[8] Forschungszentrum Julich, IEF Plasmaphys, TEC, Assoc EURATOM FZJ, D-52425 Julich, Germany