[1] EFDA CSU Garching, D-85748 Garching, Germany
[2] Assoc Euratom Confederat Suisse, Ctr Rech & Phys Plasmas, EPFL, CH-5232 Villigen, Switzerland
[3] UKAEA Fus Assoc, EURATOM, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England
[4] Inst Materialforsch, Forschungszentrum Karlsruhe, D-76021 Karlsruhe, Germany
[5] Univ Leoben, Dept Metallphys, A-8700 Leoben, Austria
[6] Univ Leoben, Erich Schmid Inst Mat Wissensch, Osterreichischen Akad Wissensch, A-8700 Leoben, Austria