1. Naka Fusion Institute, National Institutes for Quantum Science and Technology, 311-0193 Naka, Ibaraki, Japan
2. Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
3. Department of Astrophysical Sciences, Princeton University, Princeton, New Jersey 08544, USA
4. National Institute for Fusion Science, National Institutes of Natural Sciences, 509-5292, Toki, Gifu, Japan