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Kawachi, Tetsuya; Nishikino, Masaharu; Sasaki, Akira; Ishino, Masahiko; Hasegawa, Noboru; Imazono, Takashi; Pikuz, T.; Faenov, A. Ya.*; Magnitskiy, S.*; Maruyama, Momoko; et al.
no journal, ,
Laser-driven X-ray sources are widely used in probing substances for new material development etc. Besides the laser-driven sources have potentials to downsizing and ultra-short duration, we carry out the coherent X-ray research, i.e., soft X-ray lasers and higher order harmonics generation (HHG) and their applications. In the source study, the first observation of X-ray mirage and HHG from relativistic plasma are presented. In the applications, we show the surface dynamics of fs laser ablation of metal observed by the X-ray interferometer. Finally we mention the prospects for the future: By the financial support from government, we started upgrade of J-KAREN laser toward PW level to realize keV coherent X-ray and high energy particle beams. By use of this high peak power laser and another high average power lasers, we will explore the possibility of ultra-short-duration short-wavelength lasers and open up new applications of high average power coherent X-rays.
Ishino, Masahiko; Nishikino, Masaharu; Hasegawa, Noboru; Pikuz, T.; Skobelev, I. Y.*; Faenov, A.*; Yamagiwa, Mitsuru; Kawachi, Tetsuya
no journal, ,
To study the ablation process induced by soft X-ray laser (SXRL) and optical pulses, we irradiated the focused SXRL pulses having a wavelength of 13.9 nm or the focused optical light from plasma source to the material surfaces. The total energies of both pulses were almost the same. The optical spectra (visible range) of emission from the irradiated surfaces were measured by a camera. The ablation and modified structures caused by the single and multiple SXRL pulses were confirmed on irradiated surfaces. However, the optical emissions from the surfaces during the pulse irradiations were not observed. In the same geometry, the LiF surface was not modified by the optical irradiation, but scattered visible light was observed. The experimental result investigated by our study is consistent with the theoretical calculations.
Nishikino, Masaharu; Hasegawa, Noboru; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Tomita, Takuro*; Hatomi, Daiki*; Onishi, Naofumi*; Ito, Atsushi*; Minami, Yasuo*; Baba, Motoyoshi*; et al.
no journal, ,
The dynamical process of laser-induced surface modification such as the laser ablation comes to attract much attention for the micro processing by the ultra-short laser pulse. In order to observe the surface morphological change during the fs laser ablation process with a weakly excitation, we have developed soft X-ray interferometer and reflectometer system. Weakly excited ablation processes of the gold (Au) films are investigated by using single shot pump and probe imaging technique, using a Ti:Sapphire laser pulse with the duration of 80 fs pulse at a central wavelength of 795 nm for the pumping of ablation and the laser-driven soft X-ray laser at the wavelength of 13.9 nm for the probe. We discuss the scenario of the weakly excited femtosecond laser ablation of the gold surface. The numerical simulation study of the fs laser ablation process is underway by using a parallel molecular dynamics code.