Low-threshold ablation of dielectrics irradiated by ultrashort pulses of soft X-ray transient collisional and free electron lasers; Observation and modeling

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

Theoretical and experimental studies of ablation of LiF crystal by X-ray laser and FEL beams were provided. It was found a very low ablation threshold for both types of irradiation. Such a small threshold is one order of magnitude less than the one obtained for X-ray ablation by longer (nanoseconds) pulses or 2 orders smaller than arradiated by fs visible 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.