Low-threshold ablation of dielectrics irradiated by picosecond soft X-ray laser pulses; Observation and modeling

Faenov, A. Y.; Pikuz, T. A.*; Inogamov, N. A.*; Zhakhovski, V.*; Khokhlov, V.*; Anisimov, S. I.*; Fortov, V. E.*; Kato, Yoshiaki* ; Fukuda, Yuji; Tanaka, Momoko; Kishimoto, Maki; Ishino, Masahiko; Nishikino, Masaharu; Bulanov, S. V.; Kawachi, Tetsuya

The results of theoretical and experimental studies of ablation of LiF crystal by X-ray beam having photons with 89.3 eV and very short duration of pulse 7 ps are presented. It is found that the crater is formed for fluencies above the threshold 10 mJ/cm. Such a small threshold is one order of magnitude less than the one obtained for X-ray ablation by longer (nanoseconds) pulses. The theory explains this dramatic difference as a change-over from more energy consuming evaporative ablation to spallative ablation, when the pulse duration decreases from ns to ps time ranges.