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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：55.52(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.
Sumita, Junya; Fujita, Ichiro; Shibata, Taiju; Makita, Taiyo*; Takagi, Takashi*; Kunimoto, Eiji*; Sawa, Kazuhiro; Kim, W. J.*; Park, J. Y.*
IOP Conference Series; Materials Science and Engineering, 18(16), p.162010_1 - 162010_4, 2011/09
Times Cited Count：1 Percentile：52.78(Materials Science, Ceramics)For control rod element of Very High Temperature Reactor, carbon fiber reinforced carbon matrix composite (C/C composite) is one of the major candidate materials for its high strength and thermal stability. Since the crack propagation of the C/C composite is complicated, the fracture behavior is one of the most important subjects of the design methodology for the control rod with the C/C composite. In this study, in order to assess the Mode-II fracture behavior of the two-dimensional (2D-) C/C composite which has the layer structure of laminas composed of fibers and matrix, bending test with oxidized end notched flexure specimen was carried out. The interlaminar fracture toughness decreased with increasing the oxidation for the 2D-C/C composite. The oxidized matrix causes reduction of fracture toughness and the reduction ratio is dependent on the matrix type. The crack initiates at the boundary between fiber bundles and grows along them without breaking the fiber. It is thought that the cracks which were initiated at the interface between matrix and fiber were gathered into the voids in the boundary between fiber bundles, and then the crack grows up in the matrix.
Shibata, Taiju; Sumita, Junya; Makita, Taiyo*; Takagi, Takashi*; Kunimoto, Eiji*; Sawa, Kazuhiro; Kim, W. J.*; Jung, C. H.*; Park, J. Y.*
Nihon Kikai Gakkai Rombunshu, A, 76(764), p.383 - 385, 2010/04
no abstracts in English
Shibata, Taiju; Sumita, Junya; Makita, Taiyo*; Takagi, Takashi*; Kunimoto, Eiji; Sawa, Kazuhiro; Park, Y.*; Kim, W. J.*; Jung, C. H.*
no journal, ,
no abstracts in English
Kim, W. J.*; Seo, M.-R.*; Park, J. Y.*; Sumita, Junya; Shibata, Taiju; Sawa, Kazuhiro
no journal, ,
Carbon-carbon (C/C) composites have been widely used for high-temperature structural applications because they possess excellent mechanical properties such as high specific strength and thermal shock resistance. In the nuclear industry, the composites have also been considered for plasma facing materials in fusion reactors and high-temperature structural parts in gas cooled reactors. In the high-temperature gas cooled reactor, the composites are being considered for the application of various high-temperature structural parts such as control rod components, core restraint belts, tie rods, upper plenum shroud, hot duct insulation cover sheets, and floor blocks. However, the carbon based materials are susceptible to oxidation at temperatures above 400 
C. Therefore, the oxidation behavior and property degradation at high temperature under impure He or in air in case of accidental air ingress should be evaluated before the deployment of composites. In this study, the oxidation behavior of several nuclear-grade C/C composites was evaluated at various temperatures. Thermal and mechanical properties of the composites were also measured before and after oxidation. The oxidation experiments were performed in range of 500 to 1100 C under air or Ar atmosphere. Thermal diffusivity, flexural strength, tensile strength, and interlaminar shear strength of as-received and oxidized specimens were evaluated.
Ishino, Masahiko; Hasegawa, Noboru; Nishikino, Masaharu; Yamagiwa, Mitsuru; Kawachi, Tetsuya; Pikuz, T.; Faenov, A.*; Skobelev, I. Y.*
no journal, ,
Soft X-ray laser (SXRL) pulses were irradiated to the LiF, Al, and Cu surfaces. On all irradiated target surfaces, the surface modifications caused by the SXRL pulse irradiations were confirmed. However, the optical emission (visible range) from the surfaces during the pulse irradiations were not observed. The model calculation for the interaction between SXRL pulse and metal surface reveals the spallative ablation of target surface without plasma production. The experimental result investigated by our study is consistent with the theoretical calculations.
Kawachi, Tetsuya; Nishikino, Masaharu; Faenov, A.*; Pikuz, T.*; Ishino, Masahiko; Hasegawa, Noboru; Magnitskiy, S.*; Pirozhkov, A. S.; Esirkepov, T. Z.; Nishiuchi, Mamiko; et al.
no journal, ,
Laser-driven particle and radiation sources have unique and attractive characteristics such as ultra-short duration, high peak brilliance and potentials of downsizing of the source etc. Recent advent of high peak power lasers toward peta-watt (PW) level makes it possible for us to realize these particle and radiation sources with higher energy region, and now we are on the stage to investigate the mechanisms in detail and to start the applications of these novel sources. In this presentation, first of all, recent research activities in major high peak power laser facilities in Japan will be introduced, and then we will present research highlights in the last few years on the source development and the applications using high peak power lasers in Japan Atomic Energy Agency (JAEA) based upon Japan-Russia collaborations.
Ishino, Masahiko; Maruyama, Momoko; Hasegawa, Noboru; Nishikino, Masaharu; Tamotsu, Satoshi*; Faenov, A.*; Pikuz, T.*; Kawachi, Tetsuya; Yamagiwa, Mitsuru
no journal, ,
no abstracts in English
Ishino, Masahiko; Hasegawa, Noboru; Nishikino, Masaharu; Skobelev, I.*; Faenov, A.*; Pikuz, T.*; Inogamov, N.*; Kawachi, Tetsuya; Yamagiwa, Mitsuru
no journal, ,
no abstracts in English
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.
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
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, ,
Aoyagi, Noboru; Nakada, Masami; Kumagai, Yuta; Watanabe, Masayuki; Nguyen, T. T.*; Nguyen, V. T.*; Nguyen, T. H.*; Le, B. T.*
no journal, ,
We demonstrate mineral characterization of rare earth-containing ores from Yen Phu mine, using microscopic and spectroscopic techniques: SEM-EDX, M
ssbauer spectroscopy, FT-IR microscopy, and time-resolved laser-induced fluorescence spectroscopy (TRLFS). The results of Mssbauer spectroscopy indicate formation of magnetite-like, hematite-like, and iron(III) salt phases in common with three ores sampled at different points in the mine. Around the grain boundary in the magnetite-like mineral phase the presence of phosphate bands were confirmed by FT-IR microscopy. The chemical state of the rare earth species has not been entirely obtained through these methods. However, the results of TRLFS analysis on Eu imply that the Eu species are identical in the different phases observed by Mssbauer spectroscopy.
