論文 - 中井　光男

Mechanical design of experimental apparatus for FIREX cryo-target cooling 査読

A. Iwamoto, T. Norimatsu, M. Nakai, H. Sakagami, S. Fujioka, H. Shiraga, H. Azechi

9TH INTERNATIONAL CONFERENCE ON INERTIAL FUSION SCIENCES AND APPLICATIONS (IFSA 2015)   717   2016年

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Mechanical design of an experimental apparatus for FIREX cryo-target cooling is described. Gaseous helium (GHe) sealing system at a cryogenic environment is an important issue for laser fusion experiments. The dedicated loading system was designed for a metal gasket. We take U-TIGHTSEAL((R)) (Usui Kokusai Sangyo Kaisha. Ltd.) with an indium plated copper jacket as an example. According to its specification, a linear load of 110 N/m along its circumference is the optimum compression; however a lower load would still maintain helium (He) leak below the required level. Its sealing performance was investigated systematically. Our system demanded 27 N/mm of the load to keep He leak tightness in a cryogenic environment. Once leak tightness was obtained, it could be reduced to 9.5 N/mm.

Mitigation of Laser Imprinting with Diamond Ablator for Direct-Drive Inertial Confinement Fusion Targets 査読

K. Shigemori, H. Kato, M. Nakai, R. Hosogi, T. Sakaiya, H. Terasaki, S. Fujioka, A. Sunahara, H. Azechi

8TH INTERNATIONAL CONFERENCE ON INERTIAL FUSION SCIENCES AND APPLICATIONS (IFSA 2013)   688   2016年

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We propose a novel scheme to mitigate the initial perturbation imprinting due to irradiation non-uniformity. Diamond was potential candidate for the ablator material for ICF targets due to its stiffness. The stiffness is very important parameter for imprint mitigation because the laser imprint is primary as a function of pressure perturbation due to lase irradiation non-uniformity. We measured the imprint amplitude of diamond foils and plastic (CH) foils. The experimental data suggest the initial imprinting is drastically mitigated for the diamond foils.

Progress Towards a Laser Produced Relativistic Electron-Positron Pair Plasma 査読

Hui Chen, J. Bonlie, R. Cauble, F. Fiuza, W. Goldstein, A. Hazi, C. Keane, A. Link, E. Marley, S. R. Nagel, J. Park, R. Shepherd, G. J. Williams, D. D. Meyerhofer, G. Fiksel, D. Barnak, P. Y. Chang, M. Nakai, Y. Arikawa, H. Azechi, S. Fujioka, S. Kojima, N. Miyanaga, T. Morita, T. Nagai, H. Nishimura, T. Ozaki, Y. Sakawa, H. Takabe, Z. Zhang, S. Kerr, R. Fedosejevs, Y. Sentoku, M. P. Hill, D. J. Hoarty, L. M. R. Hobbs, S. F. James

8TH INTERNATIONAL CONFERENCE ON INERTIAL FUSION SCIENCES AND APPLICATIONS (IFSA 2013)   688   2016年

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A set of experiments has been performed exploring unique characteristics of pair jets and plasmas at several energetic short-pulse laser facilities including Titan at Livermore and OMEGA EP in Rochester, as well as the Osaka LFEX and AWE Orion lasers. New results are summarized, including positron beam emittance, scaling of pair production vs. laser energy, and initial results on the pair jet collimation using electromagnetic fields.

Quantitative K alpha line spectroscopy for energy transport in ultra-intense laser plasma interaction 査読

Z. Zhang, H. Nishimura, S. Fujioka, Y. Arikawa, M. Nakai, H. Chen, J. Park, G. J. Williams, T. Ozaki, H. Shiraga, S. Kojima, T. Johzaki, A. Sunahara, N. Miyanaga, J. Kawanaka, Y. Nakata, T. Jitsuno, H. Azechi

8TH INTERNATIONAL CONFERENCE ON INERTIAL FUSION SCIENCES AND APPLICATIONS (IFSA 2013)   688   2016年

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Absolute Ka line spectroscopy is proposed for studying laser-plasma interactions taking place in the cone-guided fast ignition targets. X-ray spectra ranging from 20 to 100 keV were quantitatively measured with a Laue spectrometer. The absolute sensitivities of the Laue spectrometer system were calibrated using pre-characterized laser-produced x-ray sources and radioisotopes. The integrated reflectivity for the crystal is in good agreement with predictions by an open code for x-ray diffraction. The energy transfer efficiency from incident laser beams to hot electrons, as the energy transfer agency, is derived as a consequence of this work. The absolute yield of Au and Ta Ka lines were measured in the fast ignition experimental campaign performed at Institute of Laser Engineering, Osaka University. Applying the hot electron spectrum information from the electron spectrometer, an energy transfer efficiency of the incident LFEX [1], a kJ-class PW laser, to hot electrons was derived for a planar and cone-guided geometry.

The diagnostics of the energy coupling efficiency in the Fast Ignition integrated experiment 査読

Y. Arikawa, S. Fujioka, A. Morace, Z. Zhang, T. Nagai, M. Taga, Y. Abe, S. Kojima, S. Sakata, H. Inoue, M. Utsugi, S. Hattori, S. H. Lee, T. Ikenouchi, T. Hosoda, A. Sunahara, T. Ozaki, T. Johzaki, H. Nagatomo, K. Yamanoi, T. Shimizu, S. Tokita, Y. Fujimoto, J. Kawanaka, Y. Nakata, M. Nakai, H. Shiraga, H. Jitsuno, N. Sarukura, N. Miyanaga, T. Norimatsu, H. Nishimura, H. Azechi

8TH INTERNATIONAL CONFERENCE ON INERTIAL FUSION SCIENCES AND APPLICATIONS (IFSA 2013)   688   2016年

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The energy coupling efficiency (CE) in Fast Ignition (FI) laser fusion was studied at GEKKO XII and LFEX laser facility by using newly developed targets and plasma diagnostic instruments. The gated-liquid scintillator neutron detectors had been upgraded by using neutron collimators for intense background fluxes of gamma-rays and neutrons in the FI experiment. Clear fusion neutron signal was successfully recorded in the sub-kJ heating FI experiment. Up to 5 times neutron yield enhancement was observed, and the CE of the heating laser to core plasma was estimated to be 1.6 % for cone-in-shell target implosion by 9 beams and core heating by LFEX pulse 115 ps before bang time. The laser-to-electron energy conversion efficiency was separately diagnosed using a newly developed target and resulted to be 45 %. The fast electron energy spectrum was estimated to be 2.3 MeV slope temperature by hard x-ray spectroscopy. Monte Carlo simulations demonstrate the consistency of the data set.

非一様レーザー照射によるダイヤモンド表面形状の時間発展

加藤 弘樹, 重森 啓介, 植田 ����智, 長友 英夫, 境家 達弘, 寺崎 英紀, 弘中 陽一郎, 中井 光男, 疇地 宏

日本物理学会講演概要集   71   583 - 583   2016年

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<p>直接照射型慣性核融合では不均一レーザー照射によるインプリントレベルが、点火条件を決める物理量（発生中性子数、ターゲット面密度）と関係し、重要なファクターとなっている。本研究では、ダイヤモンドとプラズマの界面に生じるインプリント擾乱の定量的評価、さらに照射強度分布と高Z表面コートの依存性について実験を行った。講演では、モデルやシミュレーションを通して観測結果に対する解釈について報告する。</p>

Heating efficiency evaluation with mimicking plasma conditions of integrated fast-ignition experiment 査読

Shinsuke Fujioka, Tomoyuki Johzaki, Yasunobu Arikawa, Zhe Zhang, Alessio Morace, Takahito Ikenouchi, Tetsuo Ozaki, Takahiro Nagai, Yuki Abe, Sadaoki Kojima, Shohei Sakata, Hiroaki Inoue, Masaru Utsugi, Shoji Hattori, Tatsuya Hosoda, Seung Ho Lee, Keisuke Shigemori, Youichiro Hironaka, Atsushi Sunahara, Hitoshi Sakagami, Kunioki Mima, Yasushi Fujimoto, Kohei Yamanoi, Takayoshi Norimatsu, Shigeki Tokita, Yoshiki Nakata, Junji Kawanaka, Takahisa Jitsuno, Noriaki Miyanaga, Mitsuo Nakai, Hiroaki Nishimura, Hiroyuki Shiraga, Hideo Nagatomo, Hiroshi Azechi

PHYSICAL REVIEW E   91 ( 6 )   2015年6月

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A series of experiments were carried out to evaluate the energy-coupling efficiency from heating laser to a fuel core in the fast-ignition scheme of laser-driven inertial confinement fusion. Although the efficiency is determined by a wide variety of complex physics, from intense laser plasma interactions to the properties of high-energy density plasmas and the transport of relativistic electron beams (REB), here we simplify the physics by breaking down the efficiency into three measurable parameters: (i) energy conversion ratio from laser to REB, (ii) probability of collision between the REB and the fusion fuel core, and (iii) fraction of energy deposited in the fuel core from the REB. These three parameters were measured with the newly developed experimental platform designed for mimicking the plasma conditions of a realistic integrated fast-ignition experiment. The experimental results indicate that the high-energy tail of REB must be suppressed to heat the fuel core efficiently.

Quantitative K alpha line spectroscopy for energytransport in fast ignition plasma driven with LFEX PW laser 査読

Z. Zhang, H. Nishimura, S. Fujioka, Y. Arikawa, T. Ikenouchi, M. Nakai, H. Nagatomo, H. Chen, J. Park, G. J. Williams, T. Ozaki, H. Shiraga, S. Kojima, H. Hosoda, N. Miyanaga, J. Kawanaka, Y. Nakata, T. Jitsuno, H. Azechi

HIGH ENERGY DENSITY PHYSICS   15   78 - 81   2015年6月

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Quantitative high-energy X-ray spectroscopy is applied for the laser plasma interaction in the fast ignition scheme. A double tracer layer target is designed for the absolute measurement of hot electron temperature and laser energy transfer efficiency. The hot electron temperature is determined from the ratio of the number of K alpha photons from the first and second tracers. Consequently, the energy transfer efficiency from incident laser beams to hot electrons, as the energy transfer mechanism, is derived. In a cone-guide geometry, we simultaneously measured the hot electron temperature and the energy transfer efficiency from the incident LFEX, a kJ-class PW laser, which were measured to be 5.3 MeV and 37%, respectively. (C) 2015 Elsevier B.V. All rights reserved.

Response measurement of single-crystal chemical vapor deposition diamond radiation detector for intense X-rays aiming at neutron bang-time and neutron burn-history measurement on an inertial confinement fusion with fast ignition 査読

T. Shimaoka, J. H. Kaneko, Y. Arikawa, M. Isobe, Y. Sato, M. Tsubota, T. Nagai, S. Kojima, Y. Abe, S. Sakata, S. Fujioka, M. Nakai, H. Shiraga, H. Azechi, A. Chayahara, H. Umezawa, S. Shikata

REVIEW OF SCIENTIFIC INSTRUMENTS   86 ( 5 )   2015年5月

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A neutron bang time and burn history monitor in inertial confinement fusion with fast ignition are necessary for plasma diagnostics. In the FIREX project, however, no detector attained those capabilities because high-intensity X-rays accompanied fast electrons used for plasma heating. To solve this problem, single-crystal CVD diamond was grown and fabricated into a radiation detector. The detector, which had excellent charge transportation property, was tested to obtain a response function for intense X-rays. The applicability for neutron bang time and burn history monitor was verified experimentally. Charge collection efficiency of 99.5% +/- 0.8% and 97.1% +/- 1.4% for holes and electrons were obtained using 5.486 MeV alpha particles. The drift velocity at electric field which saturates charge collection efficiency was 1.1 +/- 0.4 x 10(7) cm/s and 1.0 +/- 0.3 x 10(7) cm/s for holes and electrons. Fast response of several ns pulse width for intense X-ray was obtained at the GEKKO XII experiment, which is sufficiently fast for ToF measurements to obtain a neutron signal separately from X-rays. Based on these results, we confirmed that the single-crystal CVD diamond detector obtained neutron signal with good S/N under ion temperature 0.5-1 keV and neutron yield of more than 109 neutrons/shot. (C) 2015 AIP Publishing LLC.

18pCP-10 物質の圧縮率がレーザーインプリントに与える効果

加藤 弘樹, 重森 啓介, 中井 光男, 境家 達弘, 細木 亮太, 寺崎 英紀, 長友 英夫, 弘中 陽一郎, 疇地 宏

日本物理学会講演概要集   70   679 - 679   2015年

24aBH-3 燃料球内面照射型高速点火核融合の理論と点火デザイン

砂原 淳, 城崎 知至, 柳川 琢省, 坂上 仁志, 安部 勇輝, 長井 隆浩, 李 昇浩, Zhe Zhang, 池之内 孝仁, 小島 完興, 坂田 匠平, 有川 安信, 藤岡 慎介, 中井 光男, 白神 宏之, 乗松 孝好, 疇地 宏, FIREXプロジェクトチーム

日本物理学会講演概要集   70   925 - 925   2015年

22aCM-6 Study of Proton Stopping Power in Dense Plasmas

Morace A., Feugeas J-L., Nicolai P., Fujioka S., Arikawa Y., Norimatsu T., Hosokawa H., Honrubia J., Batani D., Jakubowska K., Yogo A., Nakai M., Kojima S., Zhang Z., Abe Y., Mima K., Shiraga H., Nishimura H., Azechi H.

日本物理学会講演概要集   70   861 - 861   2015年

19aCP-5 爆縮プラズマが高速電子発生に与える影響 査読

有川 安信, 側 貴行, 山本 拓未, 松尾 一輝, 戸崎 翔太, Law King Fai, 川島 丈嗣, 植田 泰智, 弘中 陽一郎, 重森 啓介, 余語 覚文, 小島 完興, 宮永 憲明, 實野 孝久, 河仲 準二, 中田 芳樹, 時田 茂樹, 長友 英夫, 西村 博明, 白神 宏之, 中井 光男, 砂原 淳, 藤岡 慎介, 城崎 知至, 尾崎 哲, 坂上 仁志, Zhe Zhang, 疇地 宏, FIREX group, LFEX group, Alessio Morace, 畑 昌育, 坂田 匠平, 安部 勇輝, 李 昇浩, 加藤 弘樹

日本物理学会講演概要集   70 ( 0 )   698 - 698   2015年

19aCP-2 ミラー型磁場を用いたレーザー生成相対論電子ビームの集束実験 査読

坂田 匠平, 有川 安信, M. Bailly-Grandvaux, C. Bellei, 尾崎 哲, 畑 昌育, 城崎 知至, 砂原 淳, 余語 覚文, 中井 光男, 西村 博明, 近藤 康太郎, 白神 宏之, 長友 英夫, J. J. Santos, 藤岡 慎介, 疇地 宏, 弘中 陽一郎, 小島 完興, 松尾 一輝, K. F. Law, S. H. Lee, A. Morace, X. Vaisseau

日本物理学会講演概要集   70 ( 0 )   695 - 695   2015年

24aBH-4 高強度レーザーのCD-shell内面照射によるホットスパーク生成実験と高速点火核融合への応用

安部 勇輝, 砂原 淳, 長井 隆浩, 李 昇浩, Zhe Zhang, 池之内 孝仁, 小島 完興, 坂田 匠平, 有川 安信, 藤岡 慎介, 中井 光男, 白神 宏之, 乗松 孝好, 疇地 宏

日本物理学会講演概要集   70   926 - 926   2015年

24pBH-6 プラズマミラーを用いた高速点火核融合高速電子発生

有川 安信, 小島 完興, 藤岡 慎介, Morace Alessio, 側 貴行, 坂田 匠平, 余語 覚文, Zhe Zhang, 時田 茂樹, 池之内 孝仁, 長井 隆浩, 安部 勇輝, 宇津木 卓, 李 昇浩, 井上 裕晶, 田口 雄基, 松尾 一輝, 戸崎 翔太, 畑 昌育, 長友 英夫, 砂原 淳, 城崎 知至, 尾崎 哲, 坂上 仁志, 井上 峻介, 寺本 研介, 中島 裕人, 橋田 昌樹, 阪部 周二, 匂坂 明人, 小倉 浩一, Pirozhkov Alexander, 錦野 将元, 近藤 公伯, 西村 博明, 白神 宏之, 中井 光男, FIREX group, LFEX group, 疇地 宏

日本物理学会講演概要集   70   953 - 953   2015年

24aCM-8 レーザー生成相対論的電子ビームの強磁場下での伝搬特性

坂田 匠平, 藤岡 慎介, 松尾 一輝, 小島 完興, Zhe Zhang, 近藤 康太郎, 城崎 知至, 田口 俊弘, 三間 圀興, 有川 安信, Morace Alessio, 長井 隆浩, 安部 勇輝, 池之内 孝仁, 尾崎 哲, 西村 博明, 中井 光男, 白神 宏之, 長友 英夫, 疇地 宏

日本物理学会講演概要集   70   940 - 940   2015年

High-intensity neutron generation via laser-driven photonuclear reaction 招待

Yasunobu Arikawa, Masaru Utsugi, Morace Alessio, Takahiro Nagai, Yuki Abe, Sadaoki Kojima, Shohei Sakata, Hiroaki Inoue, Shinsuke Fujioka, Zhe Zhang, Hui Chen, Jaebum Park, Jackson Williams, Taichi Morita, Yoichi Sakawa, Yoshiki Nakata, Junji Kawanaka, Takahisa Jitsuno, Nobuhiko Sarukura, Noriaki Miyanaga, Mitsuo Nakai, Hiroyuki Shiraga, Hiroaki Nishimura, Hiroshi Azechi

Plasma and Fusion Research   10 ( SpecialIssue.1 )   2015   2015年

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© 2015 The Japan Society of Plasma Science and Nuclear Fusion Research. The generation of high-peak-intensity neutrons through a photonuclear reaction was demonstrated using the Laser for Fast Ignition Experiments (LFEX) at Osaka University. Up to 109 neutrons/shot were generated from a 1mm sized gold target. Using Monte Carlo simulations, the neutron spectrum from keV to MeV was found to be independent of the γ-ray spectrum. The typical peak neutron intensity of 1021 neutrons /cm2/s at the target surface was estimated, and it should be a useful tool for nuclear synthesis experiments.

Laser erosion diagnostics of plasma facing materials with displacement sensors and their application to safeguard monitors to protect nuclear fusion chambers 査読

Koichi Kasuya, Shinji Motokoshi, Seiji Taniguchi, Mitsuo Nakai, Kazutoshi Tokunaga, Waldemar Mroz, Bogus Law Budner, Barbara Korczyc

XX INTERNATIONAL SYMPOSIUM ON HIGH-POWER LASER SYSTEMS AND APPLICATIONS 2014   9255   2015年

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Tungsten and SiC are candidates for the structural materials of the nuclear fusion reactor walls, while CVD poly-crystal diamond is candidate for the window material under the hazardous fusion stresses. We measured the surface endurance strength of such materials with commercial displacement sensors and our recent evaluation method. The pulsed high thermal input was put into the material surfaces by UV lasers, and the surface erosions were diagnosed. With the increase of the total number of the laser shots per position, the crater depth increased gradually. The 3D and 2D pictures of the craters were gathered and compared under various experimental conditions. For example, the maximum crater depths were plotted as a function of shot accumulated numbers, from which we evaluated the threshold thermal input for the surface erosions to be induced. The simple comparison-result showed that tungsten was stronger roughly two times than SiC. Then we proposed how to monitor the surface conditions of combined samples with such diamonds coated with thin tungsten layers, when we use such samples as parts of divertor inner walls, fusion chamber first walls, and various diagnostic windows. We investigated how we might be able to measure the inner surface erosions with the same kinds of displacement sensors. We found out the measurable maximum thickness of such diamond which is useful to monitor the erosion. Additionally we showed a new scheme of fusion reactor systems with injectors for anisotropic pellets and heating lasers under the probable use of W and/or SiC.

Characterizing a fast-response, low-afterglow liquid scintillator for neutron time-of-flight diagnostics in fast ignition experiments 査読

Y. Abe, H. Hosoda, Y. Arikawa, T. Nagai, S. Kojima, S. Sakata, H. Inoue, Y. Iwasa, K. Iwano, K. Yamanoi, S. Fujioka, M. Nakai, N. Sarukura, H. Shiraga, T. Norimatsu, H. Azechi

REVIEW OF SCIENTIFIC INSTRUMENTS   85 ( 11 )   1.10E+127   2014年11月

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The characteristics of oxygen-enriched liquid scintillators with very low afterglow are investigated and optimized for application to a single-hit neutron spectrometer for fast ignition experiments. It is found that 1,2,4-trimethylbenzene has better characteristics as a liquid scintillator solvent than the conventional solvent, p-xylene. In addition, a benzophenon-doped BBQ liquid scintillator is shown to demonstrate very rapid time response, and therefore has potential for further use in neutron diagnostics with fast time resolution. (C) 2014 AIP Publishing LLC.