High-resolution X-ray spectroscopy diagnostics of early heating stage of clusters by high contrast femtosecond laser pulse

Faenov, A.*; Pikuz, T.; Skobelev, I.*; Fortov, V.*; Colgan, J.*; Abdallah, J. Jr.*; Fukuda, Yuji; Hayashi, Yukio; Pirozhkov, A. S.; Kawase, Keigo*; Shimomura, Takuya; Kiriyama, Hiromitsu; Kato, Yoshiaki* ; Bulanov, S. V.; Kando, Masaki

A study is made of the ultra-short laser pulse irradiation of Ar and CO cluster targets. Experiments have been performed with large cluster sizes and using a variety of laser pulse durations and laser contrasts. Using very high laser contrasts of the J-KAREN laser facility allowed carrying out clear and unambiguous observation of exotic hollow ions of Ar and inner-shell transitions in near-neutral Ar ions and used them for diagnostics of early heating stage. Observation of asymmetric shapes of spectral lines of Oxygen ions also allowed to do diagnstics of early heating stage of custers irradiated by high contrast ultra-intense fs laser pulses.