1. National Institute for Fusion Science, Toki, Gifu 509-5292, Japan
2. Department of Advanced Energy Engineering, Kyushu University, Kasuga, Fukuoka 816-8580, Japan
3. EPFL–SPC, Lausanne, Switzerland
4. National Institutes for Quantum and Radiological Science and Technology, Naka, Ibaraki 311-0193, Japan