1. Institute of Laser Engineering, Osaka University, 2-6 Yamada-oka, Suita, Osaka 565-0871, Japan
2. National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu 509-5292, Japan
3. Laboratory of Advanced Science and Technology for Industry, University of Hyogo, 3-1-2 Kouto, Kamigori-cho, Ako-gun, Hyogo 678-1205, Japan