1. HRS Fusion, West Orange, New Jersey 07052, USA
2. CEA, IRFM, F-13108 Saint-Paul-lez-Durance, France
3. Princeton Plasma Physics Laboratory, Princeton, New Jersey 08570, USA
4. Consorzio RFX and Istituto Gas Ionizzati del C.N.R., 35127 Padua, Italy
5. IFTS and Department of Physics, Zhejiang University, Hangzhou 310027, China