1. Department of Nuclear Engineering, Kyoto University, Nishikyo, Kyoto 615-8530, Japan
2. Quantum Science and Engineering Center, Kyoto University, Uji, Kyoto 611-0011, Japan
3. Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan
4. Takasaki Advanced Radiation Research Institute, National Institutes for Quantum and Radiological Science and Technology (QST), Takasaki, Gunma 370-1292, Japan
5. Department of Micro Engineering, Kyoto University, Nishikyo, Kyoto 615-8530, Japan