1. Ecole Polytechnique Fédérale de Lausanne (EPFL), Swiss Plasma Center (SPC), CH-1015 Lausanne, Switzerland
2. Aix-Marseille Université CNRS, PIIM UMR 7345, 13397 Marseille, France
3. CCFE, Culham Science Centre, Abingdon, Oxon OX14 3DB, United Kingdom
4. Department of Physics, University of Maryland, College Park, Maryland 20742, USA
5. Max-Planck Institut für Plasmaphysik, Boltzmannstr. 2, D-85748 Garching, Germany
6. Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
7. Physics Department, University of Bayreuth, 95440 Bayreuth, Germany