1. National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu 509-5292, Japan
2. IsoShieldJP, Co. Ltd., YUNI-Ujigawa-704, Nishinaka-33, Kohata, Uji-shi, Kyoto 611-0002, Japan
3. Radioisotope Research Center, Kyoto University, Kyoto 606-8501, Japan
4. School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan