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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：54.39(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：54.39(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：33.34(Optics)Jinno, Satoshi; Fukuda, Yuji; Sakaki, Hironao; Yogo, Akifumi; Kanasaki, Masato; Kondo, Kiminori; Faenov, A. Y.; Skobelev, I. Yu.*; Pikuz, T.; Boldarev, A. S.*; et al.
Progress in Ultrafast Intense Laser Science XI; Springer Series in Chemical Physics, Vol.109, p.215 - 233, 2015/00
Clusters formed in supersonic gas expansion through a three-staged conical nozzle have been verified by measuring the angular distribution of the light scattered from cluster target. The size distirbutions of the clusters are calculated based on the Mie theory. The reliability of the size measurement is verified to be an experimental error of 10% using standard particles. The mean sizes of CO
clusters for the cases of CO/H and CO/He mixed-gas targets are estimated to be 0.26 
m and 0.22 m, respectively. For the CO/H, the cluster density is estimated to be 5.5 
clusters/cm
by measuring the attenuation of the laser beam intensity. Furthermore, total gas density profiles are obtained via the Abel inversion from the phase shift of the light passing through the target using an interferometer. The variation of the cluster mass fraction along the radial direction of the target is almost constant, which is consistent with a Boldarev's model.
Pirozhkov, A. S.; Kando, Masaki; Esirkepov, T. Z.; Faenov, A. Y.*; Pikuz, T. A.*; Kawachi, Tetsuya; Sagisaka, Akito; Koga, J. K.; Mori, Michiaki; Kawase, Keigo*; et al.
RAL-TR-2015-025, P. 22, 2015/00
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：10 Percentile：36.99(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：98.55(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.
Safronova, A. S.*; Kantsyrev, V. L.*; Faenov, A. Y.; Safronova, U. I.*; Wiewior, P.*; Renard-Le Galloudec, N.*; Esaulov, A. A.*; Weller, M. E.*; Stafford, A.*; Wilcox, P.*; et al.
High Energy Density Physics, 8(2), p.190 - 195, 2012/06
Times Cited Count：8 Percentile：32.63(Physics, Fluids & Plasmas)Ishino, Masahiko; Faenov, A. Y.*; Tanaka, Momoko; Hasegawa, Noboru; Nishikino, Masaharu; Tamotsu, Satoshi*; Pikuz, T.; Oba, Toshiyuki*; Kaihori, Takeshi; Kawachi, Tetsuya
Journal of Laser Micro/Nanoengineering, 7(2), p.147 - 151, 2012/05
Times Cited Count：5 Percentile：27.42(Nanoscience & Nanotechnology)We irradiated the soft X-ray laser (SXRL) pulses having a wavelength of 13.9 nm, the duration time of 7 ps to aluminum (Al), copper (Cu) and gold (Au) surfaces. After the irradiation processes of SXRL beam with laser flux of 
14 mJ/cm
for Al case and of 21 mJ/cm for Cu and Au cases, the modified surfaces were observed with the visible microscope, the scanning electron microscope, and the atomic force microscope. The surface modifications caused by the SXRL irradiations were clearly seen on the surfaces, and it was found that the conical structures having around 100 nm in diameters were formed on the Al surface under a single pulse shot. The conical structures were formed in the features with the average depth of about 40 nm, and this value was in accordance with the attenuation length of the SXRL beam for Al. The modified structure on Al surface induced by SXRL pulse irradiations is different from those of Cu and Au surfaces. The modified structure formed on Al surface induced by the SXRL pulse exposure is interesting as the newly structure. Hence, the SXRL beam would be a candidate for a tool of micromachining, which enable to fabricate of three dimensional structures with nano-meter size on Al surface.
Zhidkov, A. G.*; Pikuz, S. A.*; Faenov, A. Y.; Chefonov, O. V.*; Ovchinikov, A. V.*; Agranat, M. B.*; Zigler, A.*
Optics Letters, 37(5), p.884 - 886, 2012/03
Times Cited Count：3 Percentile：17.57(Optics)Kawachi, Tetsuya; Hasegawa, Noboru; Nishikino, Masaharu; Ishino, Masahiko; Imazono, Takashi; Oba, Toshiyuki; Kaihori, Takeshi; Kishimoto, Maki; Ochi, Yoshihiro; Tanaka, Momoko; et al.
X-Ray Lasers 2010; Springer Proceedings in Physics, Vol.136, p.15 - 24, 2011/12
This paper reviews recent improvement in the source development of laser-driven X-ray lasers and the applications in the research fields of material science, laser processing, X-ray imaging, and radiation damage in biological cells. In the application for material science, we have firstly observed temporal correlation between the domain structures of ferro-electric substance under the Curie temperature. In the laser processing, new X-ray laser interferometer reveals us the nano-scale surface distortion of substance pumped by a femto-second optical pulse. In the X-ray diffraction image, we have taken several static images of micro-structure of samples: now we are trying to extend the objective to nano-scale dynamics using pump and probe method. In the radiation damage of biological cells, we observed double strand break in DNA using X-ray laser exposure; this results are compared with the case using incoherent several KeV X-ray exposure.
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：32.40(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：63.10(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.
Kawase, Keigo; Kando, Masaki; Hayakawa, Takehito; Daito, Izuru; Kondo, Shuji; Homma, Takayuki; Kameshima, Takashi*; Kotaki, Hideyuki; Chen, L. M.*; Fukuda, Yuji; et al.
Nuclear Instruments and Methods in Physics Research A, 637(1, Suppl.), p.S141 - S144, 2011/05
Times Cited Count：7 Percentile：47.73(Instruments & Instrumentation)We report the present status of the sub-MeV X-ray generation via Compton backscattering by using 150-MeV electron beam and the Nd:YAG laser. In particular, we show the result of the X-ray generation experiment and of the laser pulse compression for increasing the X-ray flux.
Starikov, S. V.*; Stegailov, V. V.*; Norman, G. E.*; Fortov, V. E.*; Ishino, Masahiko; Tanaka, Momoko; Hasegawa, Noboru; Nishikino, Masaharu; Oba, Toshiyuki*; Kaihori, Takeshi; et al.
JETP Letters, 93(11), p.642 - 647, 2011/04
Times Cited Count：25 Percentile：75.00(Physics, Multidisciplinary)
emissions from micron-sized Kr cluster target irradiated with intense femtosecond laser pulsesHayashi, Yukio; Fukuda, Yuji; Faenov, A. Y.*; Kando, Masaki; Kawase, Keigo; Pikuz, T. A.*; Homma, Takayuki; Daido, Hiroyuki; Bulanov, S. V.
Japanese Journal of Applied Physics, 49(12), p.126401_1 - 126401_3, 2010/12
Times Cited Count：12 Percentile：45.18(Physics, Applied)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：75.98(Materials Science, Multidisciplinary)Kawase, Keigo; Kando, Masaki; Hayakawa, Takehito; Daito, Izuru; Kondo, Shuji; Homma, Takayuki; Kameshima, Takashi*; Kotaki, Hideyuki; Chen, L. M.*; Fukuda, Yuji; et al.
JAEA-Conf 2010-002, p.95 - 98, 2010/06
At the previous symposium in Advanced Photon Research, we proposed and demonstrated the laser pulse compression via stimulated Brillouin scattering (SBS) for increasing the flux of the Compton backscattered X rays. After that, we improved the SBS pulse compression system by introducing the image relay in the laser transport line. As a result, we achieve the stably compressed laser pulse with a duration of 2.1 ns and with an energy of 0.84 J. By installing this system into the Compton backscattered X-ray source, the X-ray flux will be increased 3.2 times for the present system at the KPSI-JAEA.
Faenov, A. Y.; Pikuz, T.*; Fukuda, Yuji; Kando, Masaki; Kotaki, Hideyuki; Homma, Takayuki; Kawase, Keigo; Skobelev, I.*; Gasilov, S.*; Kawachi, Tetsuya; et al.
Japanese Journal of Applied Physics, 49(6), p.06GK03_1 - 06GK03_5, 2010/06
Times Cited Count：8 Percentile：33.83(Physics, Applied)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：61.36(Physics, Fluids & Plasmas)