Ablation of insulators under the action of short pulses of X-ray plasma lasers and free-electron lasers

Inogamov, N. A.*; Anisimov, S. I.*; Petrov, Y. V.*; Khokhlov, V. A.*; Zhakhovskii, V. V.*; Faenov, A. Ya.*; Pikuz, T.; Fortov, V. E.*; Skobelev, I. Y.*; Kato, Yoshiaki* ; Shepelev, V. V.*; Fukuda, Yuji; Tanaka, Momoko; Ishino, Masahiko; Nishikino, Masaharu; Kando, Masaki; Kawachi, Tetsuya; Kishimoto, Maki; Nagasono, Mitsuru*; Tono, Kensuke*; Ishikawa, Tetsuya*; Ohashi, Haruhiko*; Yabashi, Makina*; Togashi, Tadashi*; Semba, Yasunori*

An experimental and theoretical study has been carried out of the ablation of a solid insulator with a wide band gap (LiF) under the action of ultrashort laser pulses of the UV range, obtained in a free-electron laser, and the soft X-ray region, obtained in a silver-plasma laser. A comparison is made of the results obtained on the two laser systems. It is shown that the ablation threshold is about the same for both lasers. A theory is presented that explains the weak growth of the ablation mass with increasing surface energy density of the laser radiation (the fluence) in the case of X-ray lasers as a result of the transition from spallation close to the ablation threshold to evaporative ablation at high fluence values.