[1] Osaka Univ, Inst Laser Engn, Suita, Osaka 5650871, Japan
[2] Hiroshima Univ, Grad Sch Engn, Hiroshima 7398527, Japan
[3] Inst Laser Technol, Suita, Osaka 5650871, Japan
[4] Kyushu Univ, Dept Adv Energy Engn Sci, Kasuga, Fukuoka 8168580, Japan
[5] Natl Inst Nat Sci, Natl Inst Fus Sci, Toki, Gifu 5095292, Japan