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decay of unbound neutron-hole states in 
SnVaquero, V.*; Jungclaus, A.*; Doornenbal, P.*; Wimmer, K.*; Gargano, A.*; Tostevin, J. A.*; Chen, S.*; N
cher, E.*; Sahin, E.*; 志賀 慶明*; et al.
Physical Review Letters, 118(20), p.202502_1 - 202502_5, 2017/05
被引用回数：21 パーセンタイル：77.24(Physics, Multidisciplinary)Excited states in Sn were populated following one-neutron knockout reaction from an unstable 
Sn beam at the RIBF laboratory in RIKEN. In addition to the already known rays, additional strength was observed for the first time in the excitation-energy range 3.5-5.5 MeV. Since the neutron separation energy of Sn is low, this observation provides direct evidence for the radioactive decay of neutron-unbound states in this nucleus. The ability of decay to compete with neutron emission was attributed to a mismatch between the wave functions of the initial and final states in the neutron emission case. These findings suggest that in the region south-east of 
Sn, nuclear structure effects play a significant role in the decay of unbound states, which are instead usually ignored in the evaluation of neutron-emission probabilities in astrophysical simulations.
Faenov, A.*; 松林 政仁; Pikuz, T.*; 福田 祐仁; 神門 正城; 安田 良; 飯倉 寛; 野島 健大; 酒井 卓郎; 塩澤 方浩*; et al.
High Power Laser Science and Engineering, 3, p.e27_1 - e27_9, 2015/10
被引用回数：10 パーセンタイル：49.69(Optics)This paper describes an overview of our recent discovery - clear demonstration that LiF crystals can be efficiently used as a high-performance neutron imaging detector based on optically stimulated luminescence of color centers generated by neutron irradiation. It is shown that the neutron images we have obtained are almost free from granular noise, have a spatial resolution of 5.4 
m and a linear response with a dynamic range of at least 10
. The high contrast and good sensitivity of LiF crystals allow us to distinguish two holes with less than 2% transmittance difference. We propose to use such detectors in areas where high spatial resolution with high image gradation resolution is needed, including diagnostics of different plasma sources such as laser and z-pinch produced plasmas.
Pirozhkov, A. S.; 神門 正城; Esirkepov, T. Z.; Faenov, A. Y.*; Pikuz, T. A.*; 河内 哲哉; 匂坂 明人; Koga, J. K.; 森 道昭; 川瀬 啓悟*; et al.
RAL-TR-2015-025, P. 22, 2015/00
We provide a description of experiments performed with the J-KAREN and Astra Gemini lasers where we discovered a new regime of relativistic high-order harmonic generation by multi-terawatt femtosecond lasers in gas targets. The results were explained using particle-in-cell simulations and catastrophe theory. Our work paves the way towards a bright coherent X-ray source based on compact lasers and accessible, repetitive, and debris-free gas jet targets. Such a source will be crucial for fundamental research and numerous applications requiring pumping, probing, imaging of microscopic objects and for attosecond science.
Pirozhkov, A. S.; 神門 正城; Esirkepov, T. Z.; Gallegos, P.*; Ahmed, H.*; Ragozin, E. N.*; Faenov, A. Ya.*; Pikuz, T. A.*; 河内 哲哉; 匂坂 明人; et al.
New Journal of Physics (Internet), 16(9), p.093003_1 - 093003_30, 2014/09
被引用回数：30 パーセンタイル：81.06(Physics, Multidisciplinary)We present a detailed description of our discovery of a new regime of high-order harmonic generation, including experimental data, simulations, and description of new harmonic generation mechanism. The harmonics are generated by multi-terawatt relativistic-irradiance (
10
W/cm
) femtosecond (
30-50 fs) lasers focused to gas jet targets. According to our model, the harmonics are produced by sharp, structurally stable, oscillating electron spikes at the joint of boundaries of wake and bow waves excited by the laser pulse.
Magnitskiy, S.*; Nagorskiy, N.*; Faenov, A.*; Pikuz, T.; 田中 桃子; 石野 雅彦; 錦野 将元; 福田 祐仁; 神門 正城; 河内 哲哉; et al.
Nature Communications (Internet), 4, p.1936_1 - 1936_7, 2013/06
被引用回数：5 パーセンタイル：29.23(Multidisciplinary Sciences)プラズマベースの過渡利得電子衝突励起方式のX線レーザーの発展により、小型でコヒーレントなX線光源が実現するとともに、幅広い応用研究への道が開かれている。本論文において、われわれは原子力機構において開発された2段階増幅のプラズマX線レーザーの出力位置での遠視野像に、予期しない同心円状の干渉縞が観測されたことを報告する。この模様はX線領域において初めて観察された蜃気楼現象と考えることができる。われわれは、実験条件下でのX線の伝搬を表すマクスウエル=ブロッホ方程式を解く方法を開発した。その結果、仮想的な点光源から発せられるように見えるX線の蜃気楼がさらにプラズマのレーザー効果で増幅することにより今回観測した干渉縞が発現したことを見いだした。今回得られた結果は、レーザー生成プラズマにおけるX線増幅現象の物理の本質に新しい視点を落とすとともに、X線によるプラズマ診断法や極端紫外線リソグラフィー(EUV)の新しい可能性を開くものである。
Bulanov, S. V.; Esirkepov, T. Z.; 神門 正城; Koga, J. K.; 中村 龍史; Bulanov, S. S.*; Zhidkov, A.*; 加藤 義章; Korn, G.*
High-Power, High-Energy, and High-Intensity Laser Technology; and Research Using Extreme Light: Entering New Frontiers with Petawatt-Class Lasers (Proceedings of SPIE, Vol.8780), p.878015_1 - 878015_15, 2013/05
被引用回数：10 パーセンタイル：96.7(Optics)We discuss the key important regimes of electromagnetic field interaction with charged particles. The main attention is paid to nonlinear Thomson/Compton scattering regime with the radiation friction and quantum electrodynamics effects taking into account. This process opens a channel of high efficiency electromagnetic energy conversion into the hard electromagnetic radiation in the form of ultra short high power ray flashes.
Faenov, A. Ya.*; Skobelev, I. Yu.*; Pikuz, T.; Pikuz, S. A.*; Fortov, V. E.*; 福田 祐仁; 林 由紀雄; Pirozhkov, A. S.; 小瀧 秀行; 下村 拓也; et al.
Laser and Particle Beams, 30(3), p.481 - 488, 2012/09
被引用回数：11 パーセンタイル：43.57(Physics, Applied)It is shown that various spectroscopic methods based on measurements of X-ray spectra radiated from cluster targets can be used for estimation of the destruction degree of clusters by laser prepulses. These methods allow answering the important issue of preservation of the dense cluster core at the moment of the arrival of the main laser pulse. In addition, they can be used for quantitative estimation of the size of the undestroyed parts of the clusters and also for measuring the temperature and density of the preplasmas produced by the laser prepulses.
Pirozhkov, A. S.; 神門 正城; Esirkepov, T. Z.; Gallegos, P.*; Ahmed, H.*; Ragozin, E. N.*; Faenov, A. Ya.*; Pikuz, T.; 河内 哲哉; 匂坂 明人; et al.
AIP Conference Proceedings 1465, p.167 - 171, 2012/07
被引用回数：1 パーセンタイル：46.45(Physics, Applied)We experimentally demonstrate new regime of high-order harmonic generation by relativistic-irradiance lasers in gas jet targets. Bright harmonics with both the odd and even orders are emitted in the forward direction, while the base harmonic frequency is downshifted. The harmonics are generated by linearly as well as circularly polarized pulses. With the 9 TW laser, the harmonics reach 360 eV, within the "water window" spectral region. Using 120 TW laser producing 40 uJ/sr per harmonic at 120 eV, we demonstrate the photon number scalability. The experimentally demonstrated harmonics cannot be explained by previously known mechanisms. We introduce a novel high-order harmonics generation mechanism, which explains our experimental findings.
Bulanov, S. V.; Esirkepov, T. Z.; 林 由紀雄; 神門 正城; 桐山 博光; Koga, J. K.; 近藤 公伯; 小瀧 秀行; Pirozhkov, A. S.; Bulanov, S. S.*; et al.
AIP Conference Proceedings 1465, p.87 - 96, 2012/07
被引用回数：1 パーセンタイル：46.45(Physics, Applied)In the experiments on the collision of laser light and high intensity electromagnetic pulses generated by relativistic flying mirrors, with electron bunches produced by a conventional accelerator and with laser wake field accelerated electrons the studying of extreme field limits in the nonlinear interaction of electromagnetic waves is proposed. The regimes of dominant radiation reaction, which completely changes the electromagnetic wave-matter interaction, will be revealed. This will result in a new powerful source of high brightness -rays. A possibility of the demonstration of the electron-positron pair creation in vacuum in a multi-photon processes can be realized. This will allow modeling under terrestrial laboratory conditions neutron star magnetospheres, cosmological ray bursts and the Leptonic Era of the Universe.
Pikuz, T.; Faenov, A.*; Skobelev, I.*; Fortov, V. E.*; Boldarev, A.*; Gasilov, V.*; Chen, L. M.*; Zhang, L.*; Yan, W.*; Yuan, D.*; et al.
AIP Conference Proceedings 1465, p.181 - 201, 2012/07
被引用回数：0 パーセンタイル：0.13(Physics, Applied)A study is made of the ultra-short laser pulse irradiation of Ar cluster targets. Experiments have been performed with large cluster sizes and using very high laser contrasts, which have allowed clear and unambiguous observation of exotic inner-shell transitions in near-neutral Ar ions. The interaction of the main laser pulse with the unperturbed target is a necessary requirement for observing these lines. Our measurements are supported by kinetics calculations in which a very detailed atomic model is used. X-ray spectral methods have been proposed to determine the parameters of the appearing plasma at the early stages of its evolution. It has been shown that the spectra of hollow ions are the most informative in the first moments of the heating of a cluster, whereas the diagnostics of the late stages can be performed using the conventional lines of multicharged ions.
Esirkepov, T. Z.; Pirozhkov, A. S.; 神門 正城; Gallegos, P.*; Ahmed, H.*; Ragozin, E. N.*; Faenov, A.*; Pikuz, T.; 河内 哲哉; 匂坂 明人; et al.
AIP Conference Proceedings 1465, p.172 - 180, 2012/07
被引用回数：0 パーセンタイル：0.13(Physics, Applied)最近の実験で観測されたテラワットレーザーによるXUV領域の高次高調波の発生のメカニズムに関し、カタストロフィー理論を利用した船首波によるメカニズムを考案し、2DPIC計算と3DPIC計算によりその妥当性を確認した。これにより、この高次高調波生成メカニズムに基づいた、新しいXUV光及びX線源を提案した。
神門 正城; Pirozhkov, A. S.; 中村 龍史; 林 由紀雄; 小瀧 秀行; 川瀬 啓悟*; Esirkepov, T. Z.; 福田 祐仁; 桐山 博光; 岡田 大; et al.
AIP Conference Proceedings 1465, p.159 - 166, 2012/07
被引用回数：0 パーセンタイル：0.13(Physics, Applied)We report on novel method to generate ultra-short coherent X-rays using a laser-plasma interaction. Nonlinear interaction of intense laser pulses with plasma creates stable, specific structures such as electron cusps. For example wake waves excited in an underdense plasma by the laser become dense and propagate along with the laser pulse (Flying Mirror). The flying mirror can reflect a counter-propagating laser pulse and directly convert it into high-frequency radiation and compress the pulse. We have conducted experimental results using 9 TW laser with a He gas target. We observed 10
photons in the extreme ultra-violet region (12.8-22.0 nm).
Norman, G.*; Starikov, S.*; Stegailov, V.*; Fortov, V.*; Skobelev, I.*; Pikuz, T.; Faenov, A.*; 保 智己*; 加藤 義章*; 石野 雅彦; et al.
Journal of Applied Physics, 112(1), p.013104_1 - 013104_8, 2012/07
被引用回数：41 パーセンタイル：82.33(Physics, Applied)It was shown experimentally the possibility of nanostructuring (about 20 nm) of gold surface by picosecond soft X-ray single pulse with low fluence of 20 mJ/cm
. The nanometer-scale changes of the surface structure are due to the splash of molten gold under fluence gradient of the laser beam. In addition, the ablation process occurs at slightly higher fluence of 50 mJ/cm. The atomistic model of ablation is developed that reveals that the low threshold fluence of this process is due to the build-up of the high electron pressure and the comparatively low electron-ion energy relaxation rate in gold.
Pirozhkov, A. S.; 神門 正城; Esirkepov, T. Z.; Gallegos, P.*; Ahmed, H.*; Ragozin, E. N.*; Faenov, A. Ya.*; Pikuz, T.; 河内 哲哉; 匂坂 明人; et al.
Physical Review Letters, 108(13), p.135004_1 - 135004_5, 2012/03
被引用回数：69 パーセンタイル：90.73(Physics, Multidisciplinary)マルチテラワットレーザーをガスジェットターゲットに集光照射することにより「水の窓」に達する高次高調波発生を実験で示すことに成功した。数百次に達する高次高調波の強さはJ/srパルスと評価できる。このような高調波は、高強度レーザーパルスが低密度プラズマ中を相対論的な自己収束を伴って伝搬する際に、パルスによって励起される尖塔波とキャビテーションの境界の交差点で発生する電子スパイクのコヒーレント振動により生じる。このときのスパイクの先鋭さと安定度はカタスロトフ理論により説明される。発生機構はPICシミュレーションによっても確認された。
Bulanov, S. V.; Esirkepov, T. Z.; 林 由紀雄; 神門 正城; 桐山 博光; Koga, J. K.; 近藤 公伯; 小瀧 秀行; Pirozhkov, A. S.; Bulanov, S. S.*; et al.
Nuclear Instruments and Methods in Physics Research A, 660(1), p.31 - 42, 2011/12
被引用回数：71 パーセンタイル：98.1(Instruments & Instrumentation)We propose the experiments on the collision of laser light and high intensity electromagnetic pulses generated by relativistic flying mirrors, with electron bunches produced by a conventional accelerator and with laser wake field accelerated electrons for studying extreme field limits in the nonlinear interaction of electromagnetic waves.
Bulanov, S. V.; Esirkepov, T. Z.; 林 由紀雄; 神門 正城; 桐山 博光; Koga, J. K.; 近藤 公伯; 小瀧 秀行; Pirozhkov, A. S.; Bulanov, S. S.*; et al.
Plasma Physics and Controlled Fusion, 53(12), p.124025_1 - 124025_13, 2011/12
被引用回数：6 パーセンタイル：27.22(Physics, Fluids & Plasmas)We discuss the progress in the development of the extreme light sources that will open new horizons for studying a wide range of the fundamental science and astrophysics problems. The regimes of dominant radiation reaction, which completely change the electromagnetic wave-matter interaction, will be revealed, resulting in a new extremely powerful source of ultra short high brightness -ray pulses. The possibility of abundant electron-positron pair creation via the multi-photon processes, and possibility of reaching the critical field of quantum electrodynamics which would lead to the vacuum polarization and breakdown, are attracting high attention.
Bulanov, S. V.; Esirkepov, T. Z.; 林 由紀雄; 神門 正城; 桐山 博光; Koga, J. K.; 近藤 公伯; 小瀧 秀行; Pirozhkov, A. S.; Bulanov, S. S.*; et al.
Plasma Physics and Controlled Fusion, 53(12), p.124025_1 - 124025_13, 2011/11
The review is devoted to discussing progress in the development of the extreme light sources that opens new horizons for studying of a wide range of the fundamental science problems and important applications.
Pirozhkov, A. S.; 神門 正城; Esirkepov, T. Z.; Gallegos, P.*; Ahmed, H.*; Ragozin, E. N.*; Faenov, A. Ya.*; Pikuz, T.; Koga, J. K.; 桐山 博光; et al.
Proceedings of SPIE, Vol.8140, p.81400A_1 - 81400A_16, 2011/10
We present experimental results, theory, and simulations demonstrating two novel sources of coherent X-ray radiation generated in the relativistic laser ( 10 W/cm) interaction with easily accessible, repetitive, and debris-free gas jet targets. The first source, demonstrated with the 9 TW J-KAREN laser (JAEA), is based on a relativistic mirror reflecting a counter-propagating laser pulse. The second source, demonstrated with the laser power ranging from 9 to 170 TW in experiments with the J-KAREN (JAEA) and Astra Gemini (CLF, RAL) lasers, is based on high order harmonics generation by relativistic-irradiance lasers interacting with underdense plasmas.
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.*; 加藤 義章*; et al.
Journal of Optical Technology, 78(8), p.473 - 480, 2011/08
被引用回数：6 パーセンタイル：32.94(Optics)An experimental and theoretical study has been carried out of the ablation of a solid insulator with a wide band gap (LiF) under the action of ultrashort laser pulses of the UV range, obtained in a free-electron laser, and the soft X-ray region, obtained in a silver-plasma laser. A comparison is made of the results obtained on the two laser systems. It is shown that the ablation threshold is about the same for both lasers. A theory is presented that explains the weak growth of the ablation mass with increasing surface energy density of the laser radiation (the fluence) in the case of X-ray lasers as a result of the transition from spallation close to the ablation threshold to evaporative ablation at high fluence values.
contrast femtosecond-pulse laser irradiation of argon clustersColgan, J.*; Abdallah, J. Jr.*; Faenov, A. Ya.*; Pikuz, T. A.*; Skobelev, I. Yu.*; 福田 祐仁; 林 由紀雄; Pirozhkov, A. S.; 川瀬 啓悟*; 下村 拓也; et al.
High Energy Density Physics, 7(2), p.77 - 83, 2011/06
被引用回数：21 パーセンタイル：65.79(Physics, Fluids & Plasmas)巨大アルゴンクラスターに超高コントラスト比の極短パルスレーザー照射した場合における、特異的な内殼X線発生について研究を行った。観測されたX線のほぼすべての特性は、非常に厳密な原子モデルを取り込んだキネティックモデル計算によって再現された。すなわち、ほぼ中性状態のアルゴン原子からHe様アルゴンイオンまでの多様なイオン化状態を含むプラズマからX線放射がなされたことを示唆している。ほぼ中性のアルゴン原子からのX線放射は、これまでの中程度のコントラスト比のレーザーを用いた実験では観測されておらず、今回の実験で用いたレーザーのコントラスト比が非常に高かったことを反映している。
