1. Graduate School of Advanced Science and Engineering, Hiroshima University 1 , 1-4-1, Kagamiyama, Higashihiroshima, Hiroshima 739-8527, Japan
2. Division of Quantum Science and Engineering, Graduate School of Engineering, Hokkaido University 2 , Kita 13, Nishi 8, Kita-Ku, Sapporo, Hokkaido 060-8628, Japan
3. Department of Research, National Institute for Fusion Science 3 , 322-6 Oroshi-cyo, Toki, Gifu 509-5292, Japan
4. Nishina Center for Accelerator-Based Science, RIKEN, Wako 4 , Saitama 351-0198, Japan