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Low electron temperature in ablating materials formed by picosecond soft X-ray laser pulses

石野 雅彦; 長谷川 登; 錦野 将元; Pikuz, T.*; Skobelev, I. Y.*; Faenov, A.*; Inogamov, N.*; 河内 哲哉; 山極 満

X-Ray Lasers and Coherent X-Ray Sources; Development and Applications XI (Proceedings of SPIE, Vol.9589), p.958904_1 - 958904_6, 2015/09

 被引用回数:1 パーセンタイル:56.82

波長13.9nmを持つピコ秒軟X線レーザーパルスを集光照射すると、物質表面には多彩なアブレーション構造が形成される。軟X線レーザーによるアブレーション機構の解明を目指して、アブレーション物質からのプラズマ発光観察および電子温度の導出を試みた。アブレーションに伴う可視発光の観察から、アブレーションの継続時間を1,000ps以下と仮定したとき、軟X線レーザーによって加熱された物質の電子温度が1eV未満であることがわかった。また、導出した加熱物質の電子温度は、Warm Dense Matterと呼ばれる非平衡な物質状態の中でも特に低温領域にあることが判明した。発表ではアブレーション実験の現状についても述べる。


Development of an apparatus for characterization of cluster-gas targets for laser-driven particle accelerations

神野 智史; 福田 祐仁; 榊 泰直; 余語 覚文; 金崎 真聡; 近藤 公伯; 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



Very low electron temperature in warm dense matter formed by focused picosecond soft X-ray laser pulses

石野 雅彦; 長谷川 登; 錦野 将元; Pikuz, T. A.*; Skobelev, I. Y.*; Faenov, A.*; Inogamov, N. A.*; 河内 哲哉; 山極 満

Journal of Applied Physics, 116(18), p.183302_1 - 183302_6, 2014/11

 被引用回数:7 パーセンタイル:32.34(Physics, Applied)

軟X線レーザーパルスによって物質表面で起こるアブレーション物質の電子温度の導出を試みた。アブレーションに伴って発生する可視発光の計測から、軟X線レーザーの照射によって加熱される物質の電子温度は、アブレーションの継続時間を100-1000psと仮定したとき、0.4-0.7eVと見積もることができた。導出した加熱物質の電子温度は、Warm Dense Matterと呼ばれる非平衡な物質状態の中でも極低温領域にあることが判明した。この結果から、軟X線レーザーによって物質表面で起こるアブレーションは、破砕的アブレーションの中でも明瞭なプラズマ発光を伴わない現象であると結論される。


Ablation of insulators under the action of short pulses of X-ray plasma lasers and free-electron lasers

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:5 パーセンタイル:29.38(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.


Two-temperature warm dense matter produced by ultrashort Extreme Vacuum Ultraviolet-Free Electron Laser (EUV-FEL) pulse

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

 被引用回数:20 パーセンタイル:65.67(Physics, Fluids & Plasmas)



Laser ablation of gold; Experiment and atomistic simulation

Starikov, S. V.*; Stegailov, V. V.*; Norman, G. E.*; Fortov, V. E.*; 石野 雅彦; 田中 桃子; 長谷川 登; 錦野 将元; 大場 俊幸*; 海堀 岳史; et al.

JETP Letters, 93(11), p.642 - 647, 2011/04

 被引用回数:25 パーセンタイル:75.43(Physics, Multidisciplinary)

The interaction of radiation of a picosecond X-ray laser (wavelength $$lambda$$ = 13.9 nm) with targets made of a thick gold film has been studied theoretically and experimentally. It has been shown experimentally that the action of individual X-ray laser pulses with a fluence of $$F$$ $${approx}$$ 21 mJ/cm$$^{2}$$ initiates the nanostructuring of the gold surface. Explicitly taking into account the electron subsystem, we have proposed an atomistic model of ablation that makes it possible to adequately described the experimental results. The atomistic simulation involves the ion-ion potential depending on the electron temperature $$T$$$$_{e}$$. The use of such a potential makes it possible to take into account an increase in the pressure in the system with increasing $$T$$$$_{e}$$ and to reveal two laser ablation mechanisms.


Spallative ablation of dielectrics by X-ray laser

Inogamov, N. A.*; Zhakhovsky, V. V.*; Faenov, A. Ya.*; Khokhlov, V. A.*; Shepelev, V. V.*; Skobelev, I. Y.*; 加藤 義章*; 田中 桃子; Pikuz, T. A.*; 岸本 牧; et al.

Applied Physics A, 101(1), p.87 - 96, 2010/10

 被引用回数:32 パーセンタイル:75.93(Materials Science, Multidisciplinary)

A short laser pulse in wide range of wavelengths, from infrared to X-ray, disturbs electron-ion equilibrium and increases pressure in a heated layer. The case where the pulse duration $$tau$$$$_{L}$$ is shorter than acoustic relaxation time $$t$$$$_{s}$$ is considered. It is shown that this short pulse may cause thermomechanical phenomena such as spallative ablation regardless of wavelength. While the physics of electron-ion relaxation strongly depends on wavelength and various electron spectra of substances. There are spectra with an energy gap in semiconductors and dielectrics opposed to gapless continuous spectra in metals. The paper describes entire sequence of thermomechanical processes from expansion, nucleation, foaming, and nanostructuring to spallation with particular attention to spallation by X-ray pulse.


Metrology of wide field of view nano-thickness foils' homogeneity by conventional and phase contrast soft X-ray imaging

Faenov, A. Y.; Pikuz, T.*; 福田 祐仁; 神門 正城; 小瀧 秀行; 本間 隆之; 川瀬 啓悟; Skobelev, I.*; Gasilov, S.*; 河内 哲哉; et al.

Japanese Journal of Applied Physics, 49(6), p.06GK03_1 - 06GK03_5, 2010/06

 被引用回数:8 パーセンタイル:35.15(Physics, Applied)

New approach for phase-contrast imaging of nanostructures using compact femtosecond laser-produced cluster plasma devices. Novel ultrafast soft X-ray diagnostics and metrology of full areas of free standing or mesh supported nano- thickness foils or other nanostructures is demonstrated.


Interaction of short laser pulses in wavelength range from infrared to X-ray with metals, semiconductors, and dielectrics

Inogamov, N. A.*; Faenov, A. Ya.*; Zhakhovskii, V. V.*; Skobelev, I. Y.*; Khokhlov, V. A.*; 加藤 義章*; 田中 桃子; Pikuz, T. A.*; 岸本 牧; 石野 雅彦; et al.

Contributions to Plasma Physics, 51(4), p.361 - 366, 2010/05

 被引用回数:19 パーセンタイル:64.09(Physics, Fluids & Plasmas)

Laser-matter interaction is defined by an electric band structure of condensed matter and frequency of electromagnetic radiation. The thermalization processes are different for optical as compared with X-ray quanta and for metals relative to semiconductors and dielectrics, since the light absorption and electron-electron, electron-ion dynamics are sensitive to the electron population in a conduction band and the width of a forbidden gap. Although the thermalization processes are different, the final state is simply a heated matter. Laser heating creates powerful stresses in a target if duration of laser pulse $$tau$$$$_{L}$$ is short in acoustic time scale. Nucleation and material removal take place under such stresses. Such way of removal is called here the spallative ablation. Thus the spallative ablation is an ablation mechanism universally important for qualitatively different materials and quanta.


Submicron ionography of nanostructures using a femtosecond- laser-driven-cluster-based source

Faenov, A. Y.; Pikuz, T. A.*; 福田 祐仁; 神門 正城; 小瀧 秀行; 本間 隆之; 川瀬 啓悟; 亀島 敬*; Pirozhkov, A. S.; 余語 覚文; et al.

Applied Physics Letters, 95(10), p.101107_1 - 101107_3, 2009/09

 被引用回数:30 パーセンタイル:73.44(Physics, Applied)

An intense isotropic source of multicharged carbon and oxygen ions with energy above 300 keV and high quantity per shot was obtained by femtosecond Ti:Sa laser irradiation of clusters, produced by expansion of the mixed He and CO$$_{2}$$ gases in a supersonic nozzle. The source was employed for high contrast ionography images with 600 nm spatial resolution. A difference in object thickness of 100 nm was well resolved for both Zr and polymer foils.


Application of snow nanograin targets for the generation of fast ions in femtosecond laser plasma

Faenov, A. Y.; Magunov, A. I.*; Pikuz, S. A.*; Gasilov, S. V.*; Skobelev, I. Yu.*; Palchan, T.*; Zigler, A.*; Henis, Z.*

Journal of Experimental and Theoretical Physics, 107(3), p.351 - 355, 2008/09

The energy of the directed motion of multiply charged ions produced when solid targets are exposed by low-contrast femtosecond laser pulses with low intensities. The measurements are based on the recording of spatially resolved X-ray spectra for H- and He-like Oxygen ions in the target plane. Analysis of the He- and H-like ions line profiles has revealed fractions of accelerated ions in plasma with energies from several to several tens of kiloelectron volts. We show that using a layer of frozen nanometer-size water droplets as the targets leads to an effective absorption of laser pulses and a twofold rise in the energy (to 0.1 MeV) of He-like oxygen ions compared to the use of solid targets.


MUTA calculations of a laser-produced Mg hollow atom spectrum

Colgan, J.*; Abdallah, J. Jr.*; Faenov, A. Y.; Pikuz, T. A.*; Skobelev, I. Yu.*

Physica Scripta, 78(1), p.015302_1 - 015302_6, 2008/07

 被引用回数:10 パーセンタイル:55.97(Physics, Multidisciplinary)

A study is made of the spectra produced from a short-wavelengths long-pulse (nanosecond) laser incident on an Mg plasma. A very complex experimental spectrum is analyzed in detail by comparison with large-scale atomic kinetics calculations using mixed-UTA (MUTA) model.


Spectroscopic characterization of ultrashort laser driven targets incorporating both Boltzmann and particle-in-cell models

Sherrill, M. E.*; Abdallah, J.*; Csanak, G.*; Dodd, E. S.*; 福田 祐仁; 赤羽 温; 青山 誠; 井上 典洋*; 上田 英樹*; 山川 考一; et al.

High-Power Laser Ablation VII (Proceedings of SPIE Vol.7005), p.70051R_1 - 70051R_11, 2008/06

A model that solves simultaneously both the electron and atomic kinetics was used to generate synthetic X-ray spectra to characterize high intensity ultrashort-laser-driven target experiments. A particle-in-cell simulation was used to model the laser interaction for both cluster and foil targets and provided the initial electron energy distribution function (EEDF) for a Boltzmann solver. Though this model suggests that both Ar cluster and Ti foil plasmas are held in a highly non-equilibrium state for both the EEDF and the ion level populations for several picoseconds, the spectral line features of the foil experiment was shown to evolve too quickly to be seen by current ultrafast time resolved spectrometers.


Phase-contrast imaging of nanostructures by soft X rays from a femtosecond-laser plasma

Gasilov, S. V.*; Faenov, A. Y.; Pikuz, T. A.*; Skobelev, I. Yu.*; Calegari, F.*; Vozzi, C.*; Nisoli, M.*; Sansone, G.*; Valentini, G.*; De Silvestri, S.*; et al.

JETP Letters, 87(5), p.238 - 242, 2008/03

 被引用回数:16 パーセンタイル:66.37(Physics, Multidisciplinary)

The possibility of phase-contrast imaging of nanostructures has been analyzed with the use of solid targets irradiated by femtosecond laser pulses as a spatially coherent soft X-ray source and a LiF crystal as an X-ray detector having both the submicron spatial resolution in a wide field of view and a high contrast. It has allowed to obtain high-quality phase-contrast X-ray images of foils with various chemical compositions and a thickness of about 100 nm.


Generation of fast ions by an efficient coupling of high power laser into snow nanotubes

Palchan, T.*; Henis, Z.*; Faenov, A. Y.; Magunov, A. I.*; Pikuz, S. A.*; Gasilov, S. V.*; Skobelev, I. Yu.*; Zigler, A.*

Applied Physics Letters, 91(25), p.251501_1 - 251501_3, 2007/12

 被引用回数:12 パーセンタイル:45.14(Physics, Applied)

Generation of fast ions in snow nanotubes irradiated by femtosecond laser pulses in the intensity range of 10$$^{16}$$ - 10$$^{17}$$ W/cm$$^{2}$$ was investigated. The fast ion energy was measured through X-ray emission spectra of multicharged ions of oxygen. The profile of the He-$$beta$$ and Ly-$$alpha$$ in He-like and H-like oxygen lines demonstrates a significant broadening, which may indicate generation of fast He-like and H-like ions with energies of up to 100 keV.


X-ray spectroscopic diagnostics of ultrashort laser-cluster interaction at the stage of the nonadiabatic scattering of clusters

Faenov, A. Y.; Magunov, A. I.*; Pikuz, T. A.*; Skobelev, I. Y.*; Giulietti, D.*; Betti, S.*; Galimberti, M.*; Gamucci, A.*; Giulietti, A.*; Gizzi, L. A.*; et al.

JETP Letters, 86(3), p.178 - 183, 2007/08

 被引用回数:5 パーセンタイル:37.75(Physics, Multidisciplinary)

X-ray spectroscopy diagnostics of laser-cluster interactions at a stage of non-adiabatical cluster expansion and formation of the spatially homogeneous plasma channel is carried out for the first time. It is shown, that X-ray line emission spectra of light elements, allows to determine parameters of the plasma formed at the time moment 10 ps from the beginning of femtosecond laser with relatively high plasma temperature Te 100 eV iand electron density Ne about 10$$^{19}$$ - 10$$^{20}$$ cm$$^{-3}$$.


Spectroscopic characterization of an ultrashort-pulse-laser-driven Ar cluster target incorporating both Boltzmann and particle-in-cell models

Sherrill, M. E.*; Abdallah, J. Jr.*; Csanak, G.*; Dodd, E. S.*; 福田 祐仁; 赤羽 温; 青山 誠; 井上 典洋*; 上田 英樹*; 山川 考一; et al.

Physical Review E, 73(6), p.066404_1 - 066404_6, 2006/06

 被引用回数:29 パーセンタイル:76.37(Physics, Fluids & Plasmas)



Coupled electron and atomic kinetics through the solution of the Boltzmann equation for generating time-dependent X-ray spectra

Sherrill, M. E.*; Abdallah, J. Jr.*; Csanak, G.*; Kilcrease, D. P.*; Dodd, E. S.*; 福田 祐仁; 赤羽 温; 青山 誠; 井上 典洋*; 上田 英樹; et al.

Journal of Quantitative Spectroscopy & Radiative Transfer, 99(1-3), p.584 - 594, 2006/05

 被引用回数:2 パーセンタイル:13.22(Optics)



Measurement of $$2l-nl$$' X-ray transitions from $$approx$$1 $$mu$$m Kr clusters irradiated by high-intensity femtosecond laser pulses

Hansen, S. B.*; Fournier, K. B.*; Faenov, A. Y.*; Magunov, A. I.*; Pikuz, T. A.*; Skobelev, I. Y.*; 福田 祐仁; 赤羽 温; 青山 誠; 井上 典洋*; et al.

Physical Review E, 71(1), p.016408_1 - 016408_9, 2005/01

 被引用回数:16 パーセンタイル:58.4(Physics, Fluids & Plasmas)

原研100TWレーザーを直径約1$$mu$$mのKrクラスターに照射し、Ne-like Krイオンの$$2l-nl$$'遷移に由来するX線スペクトルを測定した。X線スペクトルの入射レーザー光の強度に対する依存性は弱かった。このことは、クラスターの寿命(1-2ps)が、衝突イオン化で生成した多価イオンのイオン化レベルをNe-like Krまでに留めていることを示唆している。 相対論的多配置FACコードに基づいた衝突放射モデルを作成し、実験結果のシミュレーションを行った。その結果、クラスタープラズマの電子密度=10$$^{22}$$cm$$^{-3}$$,温度=数百eV,高速電子含有率=数%という結果が得られた。


Generation of X-rays and energetic ions from superintense laser irradiation of micron-sized Ar clusters

福田 祐仁; 赤羽 温; 青山 誠; 井上 典洋*; 上田 英樹; 岸本 泰明; 山川 考一; Faenov, A. Y.*; Magunov, A. I.*; Pikuz, T. A.*; et al.

Laser and Particle Beams, 22(3), p.215 - 220, 2004/07

 被引用回数:41 パーセンタイル:79.45(Physics, Applied)

マイクロメートルサイズのArクラスターに高強度レーザー(レーザー強度=10$$^{19}$$W/cm$$^2$$,パルス幅=30fs)を照射することによって発生したプラズマからの高分解能X線スペクトルを測定した。発生したHe$$_{alpha1}$$($$lambda$$=3.9491$AA , 3.14keV)$のフォトン数は、2$$times$$10$$^8$$photons/pulseであり、固体ターゲット照射時に匹敵するフォトン数であることが明らかになった。X線スペクトル測定と同時に、発生した高速多価イオンのエネルギー分布を測定した。発生した多価イオンの平均エネルギーは、約800keVであった。コントラスト比の高いレーザーパルスによって発生した高速電子はクラスターターゲットのisochoric heatingを可能にし、より高い価数のイオン生成、及び、He$$_{alpha1}$$線強度の増大をもたらすことが明らかとなった。

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