1. Dipartimento di Fisica, Università di Padova, Via Marzolo 8, 35131 Padova, Italy
2. Plasma Frontier Research Group, Energy Technology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568
3. Consorzio RFX, Euratom-ENEA Association, Corso Stati Uniti 4, 35127 Padova, Italy