Hydrodynamics driven by ultrashort laser pulse; Simulations and the optical pump - X-ray probe experiment

超短パルスレーザー駆動の流体運動; シミュレーションとポンププローブ実験

Inogamov, N. A.*; Zhakhovsky, V. V.*; 長谷川 登; 錦野 将元; 山極 満; 石野 雅彦; Agranat, M. B.*; Ashitkov, S. I.*; Faenov, A. Y.*; Khokhlov, V. A.*; Ilnitsky, D. K.*; Petrov, Yu. V.*; Migdal, K. P.*; Pikuz, T. A.*; 高吉 翔大*; 江山 剛史*; 柿本 直也*; 富田 卓朗*; 馬場 基芳*; 南 康夫*; 末元 徹*; 河内 哲哉

Inogamov, N. A.*; Zhakhovsky, V. V.*; Hasegawa, Noboru; Nishikino, Masaharu; Yamagiwa, Mitsuru; Ishino, Masahiko; Agranat, M. B.*; Ashitkov, S. I.*; Faenov, A. Y.*; Khokhlov, V. A.*; Ilnitsky, D. K.*; Petrov, Yu. V.*; Migdal, K. P.*; Pikuz, T. A.*; Takayoshi, Shodai*; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Tomita, Takuro*; Baba, Motoyoshi*; Minami, Yasuo*; Suemoto, Toru*; Kawachi, Tetsuya

Spatial structures of ablative mass flow produced by femtosecond laser pulses are studied. In experiments with a gold film, the Ti:sap laser pulse having a focal size of 100 microns on a target was used, while a soft X-ray probe pulse was utilized for diagnostics. The experimental data are compared with simulated mass flows obtained by two-temperature hydrodynamics and molecular dynamics methods. Simulation shows evolution of a thin surface layer pressurized after electron-ion thermalization, which leads to melting, cavitation and formation of spallation liquid layer. The calculated asymptotic surface velocity of this layer as a function of fluence is in reasonably good agreement with experimental data.