1. Department of Helical Plasma Research, National Institute for Fusion Science, National Institutes of Natural Sciences, 322-6 Oroshi-cho, Toki, Gifu, Japan
2. Department of Fusion Science, School of Physical Sciences, SOKENDAI (The Graduate University for Advanced Studies), 322-6 Oroshi-cho, Toki, Gifu, Japan
3. Institute of Radiation Emergency Medicine, Hirosaki University, 66-1, Hon-cho, Hirosaki, Aomori, Japan
4. Department of Engineering and Technical Services, National Institute for Fusion Science, National Institutes of Natural Sciences, 322-6 Oroshi-cho, Toki, Gifu, Japan