1. Railway Technical Research Institute, Kokubunji, Tokyo, Japan
2. Department of Applied Science and Technology, Faculty of Science and Technology, Sophia University, Kioi, Tokyo, Japan
3. High Energy Accelerator Research Organization, Tsukuba, Ibaraki, Japan
4. National Institute for Fusion Science, Toki, Gifu, Japan
5. Mayekawa MFG, Koto, Tokyo, Japan
6. Tohoku University, Aoba, Sendai, Japan