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Pikuz, T.; Faenov, A.*; 石野 雅彦; Starikov, S. V.*; Stegailov, V. V.*; Norman, G.*; Fortov, V.*; Skobelev, I.*; 保 智己*; 加藤 義章*; et al.
no journal, ,
We show experimentally the possibility of the precise nanostructuring of aluminum and gold surfaces by ultra low fluencies of single picosecond soft X-ray laser pulse. The atomistic model of ablation is developed that reveals the ultra-low threshold fluency values of this process to be an effect of the high electronic pressure build-up and the comparatively low electron-ion energy relaxation rates. Our modeling show that relatively slow electron-ionic relaxation in such metals results in maintaining of the high electron pressure in the near surface region for several picoseconds, that is sufficiently long for the development of the hydrodynamic response that causes the negative pressure region formation and the nanostructuring of a thin surface layer. Calculated ablation depth as a function of irradiation fluency is in good agreement with the experimental data presented as well as with the existing data on optical ablation.
Faenov, A.*; Pikuz, T.; Skobelev, I.*; Fortov, V.*; Colgan, J.*; Abdallah, J. Jr.*; 福田 祐仁; 林 由紀雄; Pirozhkov, A. S.; 川瀬 啓悟*; et al.
no journal, ,
A study is made of the ultra-short laser pulse irradiation of Ar and CO
cluster targets. Experiments have been performed with large cluster sizes and using a variety of laser pulse durations and laser contrasts. Using very high laser contrasts of the J-KAREN laser facility allowed carrying out clear and unambiguous observation of exotic hollow ions of Ar and inner-shell transitions in near-neutral Ar ions and used them for diagnostics of early heating stage. Observation of asymmetric shapes of spectral lines of Oxygen ions also allowed to do diagnstics of early heating stage of custers irradiated by high contrast ultra-intense fs laser pulses.
Pikuz, S. Jr.*; Wagenaars, E.*; Culfa, O.*; Dance, R.*; Rossall, A.*; Tallents, G.*; Faenov, A.*; K
mpfer, T.*; Schulze, K.*; Uschmann, I.*; et al.
no journal, ,
Aluminum K-shell spectra from solid targets were measured during an experiment at Vulcan Petawatt facility. Laser pulses of very high contrast and 150 J of energy allowed interaction studies between the very high intensive laser field and solid state. Intense emission of exotic spectral lines related to the transitions in Al hollow atoms were observed from Al targets. Specifically for 1.5 micron thin foil target the hollow atom yield dominated the resonance line emission. It is suggested that the hollow atoms were predominantly excited by the impact of keV X-ray photons generated on the front surface of the target. On the contrary, the spectra of aluminum foils buried in several microns of CH demonstrated lower K-shell emission and contained much weaker yield of hollow-atom lines. In this case the laser did not interact directly with aluminum matter, so most probably hollow atoms excited by fast electrons penetrating the target.
Koga, J. K.; Bulanov, S. V.; Esirkepov, T. Z.; Pirozhkov, A. S.; 神門 正城; Rosanov, N. N.*
no journal, ,
Photon-photon scattering is a fundamental theoretical prediction of quantum electrodynamics. However, no direct experimental measurement has been achieved at photon energies far below the rest mass energy of electrons. This can be attributed to the extremely small scattering cross section. For photon energies much less than the electron rest mass the scattering cross section increases as the sixth power of the photon energy. Therefore, measuring photon-photon scattering at higher energies is advantageous. To generate these high energy photon beams we propose using laser pulses reflected and frequency up-shifted by mirrors moving at relativistic velocities. We find that the resulting effective photon luminosities are high enough so that observing photon-photon scattering in the keV photon energy range could be possible with current/near future and next generation laser systems.
小瀧 秀行; 森 道昭; 林 由紀雄; 神門 正城; 大東 出; 福田 祐仁; Pirozhkov, A. S.; Koga, J. K.; Bulanov, S. V.
no journal, ,
Laser-driven plasma accelerators have been conceived to be the next-generation particle accelerators, promising ultrahigh field particle acceleration with a very short duration electron beam. In order to generate a stable high-quality electron beam, optical injection by collision of two laser pulses is proposed. The collision of two laser pulses generates a high-quality electron beam with high repeatability. In applications of the laser accelerated electron beam, it is necessary to generate an electron beam with high repetition rate. We succeed to generate an electron beam with 10 Hz by using a Nitrogen and Argon gas target. When we use the multi-ionization gas target, the plasma channel become longer than the channel for Helium gas target. We found that it is possible to generate a stable electron beam by using multi-ionization gas target due to the long channel.
神門 正城; Pirozhkov, A. S.; 中村 龍史; Esirkepov, T. Z.; 林 由紀雄; Pikuz, T.; Faenov, A.*; 小瀧 秀行; Koga, J. K.; Bulanov, S. V.
no journal, ,
短パルス,コヒーレント,極端紫外-軟X線を生成できる新しいX線発生法である相対論的飛翔鏡と相対論的強度での高次高調波について発表する。相対論的飛翔鏡では、2つのレーザーパルスを用いる。1つのパルスが非線形プラズマ波を励起し、もう1つのパルスがこの波によって反射される。最近、われわれはこの飛翔鏡法のレーザーエネルギーを固定した場合の最適な条件を探索した。また、われわれが発見した新しいX線発生法として相対論的強度での高次高調波生成の実験結果についても報告する。
Bulanov, S. V.
no journal, ,
In thermal plasmas, the electron density distribution in the breaking wave has a typical "peakon" form. The structure of the density singularity formed in a relativistically large amplitude plasma wave close to the wave-breaking limit leads to a refraction coefficient which has a coordinate dependence with discontinuous derivatives. This results in a non-exponentially small above-barrier reflection of an electromagnetic wave interacting with the nonlinear plasma wave. The ion acceleration by the radiation pressure of the laser pulse occurs in the form of the breaking wave. It is found that the beams of accelerated at the collisionless shock wave front ions are unstable against the Buneman-lke and the Weibel-like instabilities which result in the ion energy spectrum broadening.
西内 満美子; Pirozhkov, A. S.; 小倉 浩一; 谷本 壮*; 榊 泰直; Esirkepov, T. Z.; 余語 覚文; 福田 祐仁; 金崎 真聡; 匂坂 明人; et al.
no journal, ,
初めての薄膜と超高強度レーザー相互作用によるイオン加速実験から10年以上が経とうとしているが、67.5MeV(大型レーザー)及び25MeV(コンパクトレーザー)の記録はそれほど更新されていない。われわれは、40fs of pulse width, 8J of energy, 10
contrastのチタンサファイアレーザーを、SUS2.5
m厚みのターゲット上に10
Wcm
の強度に集光し、40MeVの陽子線加速に成功した。その結果について報告する。
Faenov, A.*; Pikuz, T.; 石野 雅彦; Starikov, S. V.*; Stegailov, V. V.*; Norman, G.*; Fortov, V. E.*; Skobelev, I. Yu.*; 保 智己*; 田中 桃子; et al.
no journal, ,
A systematic experimental study of the surface modifications resulting from the interactions of both single and multiple SXRL pulses in order to confirm the development of the modified structures during multiple shots irradiation. The interactions between single or multiple picosecond soft X-ray laser (SXRL) beam and metal (such as gold (Au), copper (Cu), and aluminum (Al)) surfaces, were investigated. Our results demonstrate that tensile stress created in metals by short X-ray pulse can produce spallative ablation of target even for drastically small X-ray fluencies, which open new opportunities for material nano processing.