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Nishikino, Masaharu; Kawachi, Tetsuya; Hasegawa, Noboru; Ishino, Masahiko; Minami, Yasuo*; Suemoto, Toru*; Onishi, Naofumi*; Ito, Atsushi*; Sato, Katsutoshi*; Faenov, A.*; et al.
X-Ray Lasers and Coherent X-Ray Sources; Development and Applications XI (Proceedings of SPIE, Vol.9589), p.958902_1 - 958902_7, 2015/09
Hasegawa, Noboru; Nishikino, Masaharu; Tomita, Takuro*; Onishi, Naofumi*; Ito, Atsushi*; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Izutsu, Rui*; Minami, Yasuo*; Baba, Motoyoshi*; et al.
X-Ray Lasers and Coherent X-Ray Sources; Development and Applications XI (Proceedings of SPIE, Vol.9589), p.95890A_1 - 95890A_8, 2015/09
Times Cited Count：1 Percentile：55.52(Optics)We have improved a soft X-ray laser (SXRL) interferometer synchronized with a Ti:Sapphire laser pulse to observe the single-shot imaging of the nano-scaled structure dynamics of the laser induced materials. By the precise imaging optics and double time fiducial system having been installed, the lateral resolution on the sample surface and the precision of the temporal synchronization between the SXRL and Ti:Sapphire laser pulses were improved to be 700 nm and 2 ps, respectively. By using this system, the initial stage (before 200 ps) of the ablation process of the Pt surface pumped by 80 fs Ti:Sapphire laser pulse was observed by the comparison between the soft X-ray reflective image and interferogram. We have succeeded in the direct observation of the unique ablation process around the ablation threshold such as the rapid increase of the surface roughness and surface vibration.
Hasegawa, Noboru; Tomita, Takuro*; Nishikino, Masaharu; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Minami, Yasuo*; Baba, Motoyoshi*; Onishi, Naofumi*; Ito, Atsushi*; Kawachi, Tetsuya; et al.
JAEA-Conf 2015-001, p.17 - 20, 2015/07
We have succeeded in simultaneous observation of the ablation front and the expansion front with thin filmy structure in the femto-second laser ablation process of a gold target by using the 13.9 nm soft X-ray probe (incident angle to the sample 
70 deg) with soft X-ray interferometer. The dependence on the laser local fluence and materials was obtained by the comparison between gold and tungsten.
Nishikino, Masaharu; Hasegawa, Noboru; Tomita, Takuro*; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Onishi, Naofumi*; Ito, Atsushi*; Baba, Motoyoshi*; Minami, Yasuo*; Kawachi, Tetsuya; et al.
Reza Gakkai Dai-471-Kai Kenkyukai Hokoku; Tanhacho Ryoshi Bimu Hassei To Sono Oyo, p.9 - 12, 2014/12
no abstracts in English
Nishikino, Masaharu; Hasegawa, Noboru; Ishino, Masahiko; Yamagiwa, Mitsuru; Kawachi, Tetsuya; Minami, Yasuo*; Terakawa, Kota*; Takei, Ryota*; Baba, Motoyoshi*; Suemoto, Toru; et al.
JAEA-Conf 2013-001, p.16 - 19, 2013/09
The dynamics of the femtosecond laser ablation is still not clear at the early stage. Several studies on the time-resolved imaging of femtosecond laser ablation process have been performed on various materials. In this study, we have demonstrated a pump and probe imaging of the metal surface morphology during the femtosecond laser ablation by using the laser-driven plasma induced soft X-ray laser (SXRL) as a probe beam. The pumping laser used for ablation was a Ti:Sapphire laser system based on chirped pulse amplification. The pump beam had a Gaussian profile and the focal spot size on the metal surface was about 70 micron at FWHM. The dependence for the pump laser fluence of the ablation surface expansion and the surface condition (roughness and density gradient) were observed from the soft X-ray interferogram and reflective image, respectively.
Nishikino, Masaharu; Hasegawa, Noboru; Tomita, Takuro*; Minami, Yasuo*; Takei, Ryota*; Baba, Motoyoshi*; Eyama, Tsuyoshi*; Takayoshi, Shodai*; Kawachi, Tetsuya; Hatomi, Daiki*; et al.
Proceedings of SPIE, Vol.8849, p.88490E_1 - 88490E_6, 2013/09
Times Cited Count：2 Percentile：73.12(Optics)We have developed the pump and probe interferometer and reflective imaging technique of the metal surfaces during the femtosecond laser ablation by using the laser-driven soft X-ray laser at the wavelength of 13.9 nm. The pumping laser used for ablation was a Ti: Sapphire laser pulse with the duration of 80 fs pulse at a central wavelength of 795 nm, and had a gaussian spatial profile. By using the X-ray imaging technique, the time resolved image of nano-scaled ablation dynamics of the platinum and the gold pumped by a femtosecond laser pulse was obtained.
Okamura, Masachika*; Hase, Yoshihiro; Onishi, Noboru*; Narumi, Issei; Tanaka, Atsushi
JAEA-Review 2011-043, JAEA Takasaki Annual Report 2010, P. 105, 2012/01
Okamura, Masachika*; Shimizu, Akira*; Onishi, Noboru*; Hase, Yoshihiro; Yoshihara, Ryohei; Narumi, Issei
JAEA-Review 2008-055, JAEA Takasaki Annual Report 2007, P. 62, 2008/11
no abstracts in English
Nishikino, Masaharu; Tanaka, Momoko; Kawazome, Hayato; Kawachi, Tetsuya; Sasaki, Akira; Hasegawa, Noboru; Ochi, Yoshihiro; Kishimoto, Maki; Nagashima, Keisuke; Onishi, Naofumi*
AIP Conference Proceedings 827, p.499 - 504, 2006/04
no abstracts in English
Nishikino, Masaharu; Tanaka, Momoko; Onishi, Naofumi*; Kawachi, Tetsuya; Nagashima, Keisuke; Kawazome, Hayato; Kishimoto, Maki; Hasegawa, Noboru; Ochi, Yoshihiro
no journal, ,
no abstracts in English
Nishikino, Masaharu; Yamamoto, Minoru*; Hasegawa, Noboru; Tomita, Takuro*; Terakawa, Kota*; Minami, Yasuo*; Takei, Ryota*; Onishi, Ryo*; Ishino, Masahiko; Kaihori, Takeshi; et al.
no journal, ,
The X-ray reflective imaging using a soft X-ray laser was used to observe the early stage of the femtosecond laser ablation process on the platinum. The fluence dependence of the soft X-ray reflectivity is classified into three regions: (1) strongly excited, (2) moderately excited, and (3) weakly excited regions. In strongly excited region, the rapid reduction of the reflectivity due to the explosive evaporation in the ablation process of the material surface was observed. In the moderately excited region, the reflectivity reduction is far slower than that in the strongly excited region. The reflectivity reduction is seemed to be caused by the growth of surface roughness on the ablation front because of the formation of nano-bubbles in the irradiated material.
Okamura, Masachika*; Onishi, Noboru*; Hase, Yoshihiro; Narumi, Issei; Sasaki, Nobuhiro*
no journal, ,
no abstracts in English
Nishikino, Masaharu; Hasegawa, Noboru; Tomita, Takuro*; Minami, Yasuo*; Takei, Ryota*; Onishi, Ryo*; Ishino, Masahiko; Yamamoto, Minoru*; Terakawa, Kota*; Kaihori, Takeshi; et al.
no journal, ,
To improve the femtosecond laser processing technique more accurate and controllable, the knowledge about the laser ablation process is important. In order to understand the dynamics of the femtosecond laser ablation process, we performed a pump and probe reflectivity imaging of the platinum surface during the femtosecond laser ablation by using the laser-driven soft X-ray laser as a probe beam. The fluence dependence of the soft X-ray reflectivity is classified into three regions: (1) strongly excited, (2) moderately excited, and (3) weakly excited regions. In strongly excited region, the rapid reduction of the reflectivity due to the explosive evaporation in the ablation process of the material surface was observed. In the moderately excited region, the reflectivity reduction is far slower than that in the strongly excited region.
Hasegawa, Noboru; Nishikino, Masaharu; Kaihori, Takeshi; Kawachi, Tetsuya; Yamagiwa, Mitsuru; Yamamoto, Minoru*; Suemoto, Toru*; Tomita, Takuro*; Minami, Yasuo*; Terakawa, Kota*; et al.
no journal, ,
We have developed the femto-second laser pump and soft X-ray laser probe system in order to observe the dynamical processes of the femto-second laser ablation. The soft X-ray is the most suitable light source for observing the solid surface morphology irradiated by ultra-short pulse laser. It is because that; (1) the critical electron density of the plasmas for the SXRL is much higher than that of optical lasers. (2) the penetration depth of SXRL is much smaller than that of hard X-ray. By using this system, we succeed to obtain the temporal evolution of the soft X-ray reflectivity from the laser induced Pt surface. The results lead that the rate of decrease in the reflectivity of the soft X-ray has a non-linear relation with the pump laser fluence.
Nishikino, Masaharu; Hasegawa, Noboru; Tomita, Takuro*; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Hatomi, Daiki*; Onishi, Naofumi*; Baba, Motoyoshi*; Kawachi, Tetsuya; Yamagiwa, Mitsuru; et al.
no journal, ,
no abstracts in English
Nishikino, Masaharu; Hasegawa, Noboru; Tomita, Takuro*; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Hatomi, Daiki*; Onishi, Naofumi*; Ito, Atsushi*; Kawachi, Tetsuya; Yamagiwa, Mitsuru; et al.
no journal, ,
no abstracts in English
Nishikino, Masaharu; Hasegawa, Noboru; Tomita, Takuro*; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Onishi, Naofumi*; Hatomi, Daiki*; Ito, Atsushi*; Minami, Yasuo*; Takei, Ryota*; et al.
no journal, ,
no abstracts in English
Yamagiwa, Mitsuru; Hasegawa, Noboru; Nishikino, Masaharu; Tomita, Takuro*; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Onishi, Naofumi*; Hatomi, Daiki*; Ito, Atsushi*; Minami, Yasuo*; et al.
no journal, ,
no abstracts in English
Hasegawa, Noboru; Nishikino, Masaharu; Tomita, Takuro*; Takei, Ryota*; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Hatomi, Daiki*; Onishi, Naofumi*; Baba, Motoyoshi*; Kawachi, Tetsuya; et al.
no journal, ,
We have observed the temporal evolution of the femto-second laser irradiated metal surface by using the soft X-ray laser probe at the wavelength of 13.9 nm. The initial dynamics of the fs-laser ablation is quite rapid ( a few ps) and the dynamics of the laser processing is kept for a long time. We have developed a new pump and probe system to measure these phenomena by the same set-up. By using this system, we have succeeded to obtain the temporal evolution of the ablation front exfoliated from the laser ablated gold surface.
Hasegawa, Noboru; Nishikino, Masaharu; Tomita, Takuro*; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Hatomi, Daiki*; Onishi, Naofumi*; Ito, Atsushi*; Minami, Yasuo*; Takei, Ryota*; et al.
no journal, ,
We have observed the temporal evolution of the femto-second laser irradiated metal surface by using the soft X-ray laser probe at the wavelength of 13.9 nm. We have succeeded to obtain the temporal evolution of the ablation front from the result of the soft X-ray reflective imaging and interferogram. We will report about "the Newton's ring generated between the ablation front and the metal surface" and "the ablation front dynamics observed by the soft X-ray shadow graph".
