1. Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching, Germany
2. Physik-Department E28, Technische Universität München, 85748 Garching, Germany
3. Dipartimento di Energia, Politecnico di Milano, Via Ponzio 34/3, 20133 Milano, Italy
4. Laboratorio Nacional de Fusión, CIEMAT, 28040 Madrid, Spain