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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.
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.
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)Inogamov, N. A.*; Zhakhovsky, V. V.*; Ashitkov, S.*; Eminov, Yu.*; Faenov, A.*; Petrov, Y. V.*; Khokhlov, V.*; Ishino, Masahiko; Demaske, B.*; Tanaka, Momoko; et al.
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Kawachi, Tetsuya; Faenov, A.*; Tanaka, Momoko; Ishino, Masahiko; Pikuz, T.*; Hasegawa, Noboru; Bulanov, S. V.; Inogamov, N. A.*; Khokhlov, V.*; Anisimov, S. I.*
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We have observed ablation threshold of materials irradiated by pico-second EUV laser pulse. The obtained ablation threshold was lower by 2-3 orders of magnitude than the cases irradiated by visible or infrared laser pulse. In order to explain the present result, we have performed computer simulation involving molecure-dynamics and hydro-dynamics. The results shows that in the case of EUV laser irradiation, high temperature and high pressure region is generated in the localized area of the materials and following generation of the strong tenssile induces spallative destruction of the material. This mechanism is completely different from the case by use of visible or infrared laser pulse.
Ishino, Masahiko; Faenov, A.*; Tanaka, Momoko; Hasegawa, Noboru; Nishikino, Masaharu; Tamotsu, Satoshi*; Pikuz, T. A.*; Inogamov, N. A.*; Zhakhovsky, V. V.*; Skobelev, I. Y.*; et al.
no journal, ,
no abstracts in English
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.
Kawachi, Tetsuya; Ishino, Masahiko; Nishikino, Masaharu; Faenov, A.*; Pikuz, T.; Hasegawa, Noboru; Inogamov, N. A.*; Skobelev, I. Y.*; Fortov, V. E.*; Khohlov, V. A.*; et al.
no journal, ,
Laser ablation has many technological applications in material processing and nano-structure fabrication. The laser-induce damage of the materials has been intensively studied and its dependence upon the pulse width, the photon energy, and the fluence has come to be understood. Recently novel light sources in soft X-ray region, i.e., laser-based soft X-ray laser (SXRL) and X-FEL, become available, and the use of these light sources provide us new possibility of laser processing. SXRL interaction with materials is quite different from that of optical lasers: Dominant absorption process is photo-ionization which creates high energy photo-electrons with around 100 eV in localized surface layer of materials, and such a temperature growth increases the tensile stress which may induce the spallation of the surface layer or unexpected surface modification. In this presentation, we report an experimental and theoretical study of SXRL ablation and nano-scale surface modification of metals.
Faenov, A. Y.; Inogamov, N. A.*; Zhakhovskii, V.*; Khokhlov, V. A.*; Nishihara, Katsunobu*; Kato, Yoshiaki*; Tanaka, Momoko; Pikuz, T.*; Kishimoto, Maki; Ishino, Masahiko; et al.
no journal, ,