1. Institute of Laser Engineering, Osaka University, Osaka 565-0871, Japan
2. Center for Material Under Extreme Environment, Purdue University, West Lafayette, Indiana 478907, USA
3. Nagoya University, Furo, Chikusa, Nagoya 464-8601, Japan
4. Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
5. Industries Development Center, Central Research Laboratory, Hamamatsu Photonics K.K., Shizuoka 431-1202, Japan
6. National Institute for Fusion Science, Toki, Gifu 509-529, Japan