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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
Ishino, Masahiko; Hasegawa, Noboru; Nishikino, Masaharu; Pikuz, T.*; Skobelev, I. Y.*; Faenov, A.*; Inogamov, N.*; Kawachi, Tetsuya; Yamagiwa, Mitsuru
X-Ray Lasers and Coherent X-Ray Sources; Development and Applications XI (Proceedings of SPIE, Vol.9589), p.958904_1 - 958904_6, 2015/09
Times Cited Count：1 Percentile：55.26(Optics)To study the ablation process induced by the soft X-ray laser pulse, we investigated the electron temperature of the ablating material. Focused soft X-ray laser pulses having a wavelength of 13.9 nm and duration of 7 ps were irradiated onto target surfaces, and we observed the optical emission from surfaces by use of an optical camera. On target surfaces, we could confirm damage structures, but no emission signal in the visible spectral range during ablation could be observed. Then, we estimated the electron temperature in the ablating matter, and we estimated the electron temperature to be lower than 1 eV and the process duration was shorter than 1000 ps. This result is in good accordance with the theoretical prediction. Our investigation implies that the spallative ablation occurs in the low electron temperature region of a non-equilibrium state of warm dense matter. We will present the current state of our eperimental results.
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：55.26(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.
Inogamov, N. A.*; Zhakhovsky, V. V.*; Hasegawa, Noboru; Nishikino, Masaharu; Yamagiwa, Mitsuru; Ishino, Masahiko; Agranat, M. B.*; Ashitkov, S. I.*; Faenov, A. Y.*; Khokhlov, V. A.*; et al.
Applied Physics B, 119(3), p.413 - 419, 2015/06
Times Cited Count：6 Percentile：34.07(Optics)Ishino, Masahiko; Hasegawa, Noboru; Nishikino, Masaharu; Pikuz, T. A.*; Skobelev, I. Y.*; Faenov, A.*; Inogamov, N. A.*; Kawachi, Tetsuya; Yamagiwa, Mitsuru
Journal of Applied Physics, 116(18), p.183302_1 - 183302_6, 2014/11
Times Cited Count：9 Percentile：37.80(Physics, Applied)We investigated the optical emission from the ablating surfaces induced by the irradiations of soft X-ray laser (SXRL) pulses with the aim of estimation of the maximum electron temperature. No emission signal in the spectral range of 400-800 nm could be observed despite the formation of damage structures on the target surfaces. Hence, we estimated an upper limit for the electron temperature of 0.4-0.7 eV for the process duration of 100-1000 ps. Our results imply that the ablation and/or surface modification by the SXRL is not accompanied by plasma formation but is induced by thermo-mechanical pressure, which is so called a spallative ablation. This spallative ablation process occurs in the low electron temperature region of a non-equilibrium state of warm dense matter.
Inogamov, N. A.*; Zhakhovsky, V. V.*; Ashitkov, S. I.*; Emirov, Y. N.*; Faenov, A. Y.*; Pikuz, T. A.*; Ishino, Masahiko; Kando, Masaki; Hasegawa, Noboru; Nishikino, Masaharu; et al.
Journal of Physics; Conference Series, 500(11), p.112070_1 - 112070_6, 2014/05
Times Cited Count：21 Percentile：98.64(Physics, Applied)The mechanism of formation and geometry of surface structures are discussed for the case of single pulse acting on a well-polished metal surface. We demonstrate that the complex surface nano-structures are formed after laser irradiation due to the thermomechanical spallation of ultrathin surface layer of melt. Spallation is accompanied by a strong foaming of melt followed by breaking of the foam. After several nanoseconds the foam remnants freeze up with formation of complex nano-structures on a target surface.
Ishino, Masahiko; Faenov, A.*; Tanaka, Momoko; Tamotsu, Satoshi*; Pikuz, T.; Hasegawa, Noboru; Nishikino, Masaharu; Inogamov, N.*; Skobelev, I.*; Fortov, V.*; et al.
Proceedings of SPIE, Vol.8849, p.88490F_1 - 88490F_8, 2013/09
Times Cited Count：2 Percentile：72.96(Optics)Ishino, Masahiko; Faenov, A.*; Tanaka, Momoko; Hasegawa, Noboru; Nishikino, Masaharu; Tamotsu, Satoshi*; Pikuz, S.*; Inogamov, N. A.*; Zhakhovsky, V. V.*; Skobelev, I.*; et al.
AIP Conference Proceedings 1465, p.236 - 240, 2012/07
Times Cited Count：2 Percentile：63.45(Physics, Applied)We irradiated the focusing soft X-ray laser pulses having a wavelength of 13.9 nm and the duration of 7 ps to aluminum surface. After the irradiation process, the irradiated surface was observed with a scanning electron microscope. The surface modifications caused by soft X-ray laser single pulse exposure were clearly seen. In addition, it was found that the conical structures having around 100 nm in diameters were formed in the shallow features. The nano-meter size modified surface structures on aluminum induced by the soft X-ray laser pulse is interesting as the newly surface structure. Hence, the soft X-ray laser beam would be a candidate for a tool of micromachining. We also provide a thermomechanical modeling of the soft X-ray laser interaction with aluminum briefly to explain the surface modification.
Inogamov, N. A.*; Anisimov, S. I.*; Petrov, Y. V.*; Khokhlov, V. A.*; Zhakhovskii, V. V.*; Faenov, A. Ya.*; Pikuz, T.; Fortov, V. E.*; Skobelev, I. Y.*; Kato, Yoshiaki*; et al.
Journal of Optical Technology, 78(8), p.473 - 480, 2011/08
Times Cited Count：6 Percentile：32.77(Optics)Inogamov, N. A.*; Faenov, A. Ya.*; Zhakhovsky, V. V.*; Pikuz, T. A.*; Skobelev, I. Yu.*; Petrov, Y. V.*; Khokhlov, V. A.*; Shepelev, V. V.*; Anisimov, S. I.*; Fortov, V. E.*; et al.
Contributions to Plasma Physics, 51(5), p.419 - 426, 2011/06
Times Cited Count：20 Percentile：63.86(Physics, Fluids & Plasmas)Warm dense matter, arising under the action of ultrashort EUV-FEL pulse onto LiF dielectric crystal, is characterized by high temperature of conduction electrons, with their number density achieving values of the order of atom number density at maximum laser fluences in our experiments. Expansion of matter, heated and pressurized through the electron-ion energy exchange, gives rise to the spallative ablation at small fluences and gaseous outflow from a target in the case of large fluences. Ablation threshold is low in comparison with a longer nanosecond XRL.
Ishino, Masahiko; Faenov, A. Ya.*; Tanaka, Momoko; Hasegawa, Noboru; Nishikino, Masaharu; Tamotsu, Satoshi*; Pikuz, T. A.*; Inogamov, N. A.*; Zhakhovskii, V. V.*; Skobelev, I. Yu.*; et al.
Journal of Applied Physics, 109(1), p.013504_1 - 013504_6, 2011/01
Times Cited Count：33 Percentile：76.79(Physics, Applied)no abstracts in English
Inogamov, N. A.*; Zhakhovsky, V. V.*; Faenov, A. Ya.*; Khokhlov, V. A.*; Shepelev, V. V.*; Skobelev, I. Y.*; Kato, Yoshiaki*; Tanaka, Momoko; Pikuz, T. A.*; Kishimoto, Maki; et al.
Applied Physics A, 101(1), p.87 - 96, 2010/10
Times Cited Count：34 Percentile：76.41(Materials Science, Multidisciplinary)Inogamov, N. A.*; Faenov, A. Ya.*; Zhakhovskii, V. V.*; Skobelev, I. Y.*; Khokhlov, V. A.*; Kato, Yoshiaki*; Tanaka, Momoko; Pikuz, T. A.*; Kishimoto, Maki; Ishino, Masahiko; et al.
Contributions to Plasma Physics, 51(4), p.361 - 366, 2010/05
Times Cited Count：19 Percentile：62.10(Physics, Fluids & Plasmas)Faenov, A. Y.; Inogamov, N. A.*; Zhakhovskii, V. V.*; Khokhlov, V. A.*; Nishihara, Katsunobu*; Kato, Yoshiaki*; Tanaka, Momoko; Pikuz, T. A.*; Kishimoto, Maki; Ishino, Masahiko; et al.
Applied Physics Letters, 94(23), p.231107_1 - 231107_3, 2009/06
Times Cited Count：44 Percentile：81.91(Physics, Applied)Ishino, Masahiko; Hasegawa, Noboru; Nishikino, Masaharu; Maruyama, Momoko; Faenov, A.*; Tamotsu, Satoshi*; Pikuz, T.*; Inogamov, N.*; Skobelev, I.*; Kawachi, Tetsuya; et al.
no journal, ,
Soft X-ray laser pulses having a wavelength of 13.9 nm and a duration of 7 ps have an ability to make various nanometer scale damage structures on material surfaces. Our experimental study confirms the theoretical model of an atomistic simulation, which predicts the splash of molten layers occurring under a low electron temperature less than 1 eV and creating nanometer scale surface modifications. We also propose the probable ideas of applications of surface structures induced by the soft X-ray laser pulses. Catalytic substrates for chemical reactions, nanopillar sheet for culturing biological cells, and geometrical structures beneath the surface will be candidates. When we can control the surface modification process, the soft X-ray laser beam will enable us to fabricate three dimensional nanometer scale structures.
Nishikino, Masaharu; Hasegawa, Noboru; Tomita, Takuro*; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Onishi, Naofumi*; Ito, Atsushi*; Baba, Motoyoshi*; Minami, Yasuo*; Inogamov, N.*; et al.
no journal, ,
Femtosecond laser ablation processes on gold and tungsten were observed by the single shot pump and probe imaging using a soft X-ray laser probe. A clear difference was found in the temporal behavior of the dynamical response of the soft X-ray reflectivity depending on the irradiated laser fluence in two materials. The duration of the femtosecond laser ablation on the tungsten is shorter than the gold case and the narrow dark rings around the crater position were found in the tungsten case. Our experimental data lead to better understanding of the initial process of the laser ablation dynamics.
Nishikino, Masaharu; Hasegawa, Noboru; Kawachi, Tetsuya; Suemoto, Toru*; Onishi, Naofumi*; Ito, Atsushi*; Inogamov, N.*; Faenov, A. Y.*
no journal, ,
no abstracts in English
Kawachi, Tetsuya; Nishikino, Masaharu; Hasegawa, Noboru; Minami, Yasuo*; Baba, Motoyoshi*; Yamagiwa, Mitsuru; Kondo, Kiminori; Inogamov, N. A.*; Zakhovsky, V.*; Faenov, A. Y.*; et al.
no journal, ,
Kawachi, Tetsuya; Faenov, A.*; Ishino, Masahiko; Tanaka, Momoko; Inogamov, N. A.*; Khokhlov, V.*; Anisimov, S. I.*; Pikuz, T.*; Hasegawa, Noboru; Nishikino, Masaharu; et al.
no journal, ,
We have observed low ablation threshold of substances illuminated by EUV laser pulse. The ablation threshold was lower by 2-3 orders of magnitude compared with the cases by use of visible or infrared laser pulse. In order to explain the present result, we have performed the computer simulation involving molecular dynamics and hydro-dynamics. The calculated results implied that in the case of EUV laser ablation, high temperature and high pressure region could be generated in localized area, and following strong tenssile stress induced spallative distruction of the substances. This mechanism is completely different from the ablation process induced by visible or infrared laser illumination.
Ishino, Masahiko; Nishikino, Masaharu; Hasegawa, Noboru; Tamotsu, Satoshi*; Faenov, A.*; Pikuz, T.*; Zhakhovsky, V.*; Skobelev, I.*; Inogamov, N.*; Kawachi, Tetsuya
no journal, ,
no abstracts in English
