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論文

3D visualization of XFEL beam focusing properties using LiF crystal X-ray detector

Pikuz, T.*; Faenov, A.*; 松岡 健之*; 松山 智至*; 山内 和人*; 尾崎 典雅*; Albertazzi, B.*; 犬伏 雄一*; 矢橋 牧名*; 登野 健介*; et al.

Scientific Reports (Internet), 5, p.17713_1 - 17713_10, 2015/12

 被引用回数:19 パーセンタイル:19.61(Multidisciplinary Sciences)

we report, that by means of direct irradiation of lithium fluoride a (LiF) crystal, in situ 3D visualization of the SACLA XFEL focused beam profile along the propagation direction is realized, including propagation inside photoluminescence solid matter. High sensitivity and large dynamic range of the LiF crystal detector allowed measurements of the intensity distribution of the beam at distances far from the best focus as well as near the best focus and evaluation of XFEL source size and beam quality factor M2. Our measurements also support the theoretical prediction that for X-ray photons with energies $$sim$$10 keV the radius of the generated photoelectron cloud within the LiF crystal reaches about 600 nm before thermalization. The proposed method has a spatial resolution 0.4-2.0 micron for photons with energies 6-14 keV and potentially could be used in a single shot mode for optimization of different focusing systems developed at XFEL and synchrotron facilities.

論文

Photoelectron diffraction from laser-aligned molecules with X-ray free-electron laser pulses

中嶋 享*; 寺本 高啓*; 赤木 浩; 藤川 高志*; 間嶋 拓也*; 峰本 紳一郎*; 小川 奏*; 酒井 広文*; 富樫 格*; 登野 健介*; et al.

Scientific Reports (Internet), 5, p.14065_1 - 14065_11, 2015/09

 被引用回数:25 パーセンタイル:17.33(Multidisciplinary Sciences)

X線自由電子レーザーを利用することで、レーザーによって整列したI$$_{2}$$分子からのX線光電子回折(XPD)パターンを観測した。X線自由電子レーザーの偏光方向に整列したI$$_{2}$$分子のXPDは我々の理論計算とよく一致した。さらに、実験で得られるXPDを分子構造決定に利用する際の適応基準を提案した。

論文

Optical features of a LiF crystal soft X-ray imaging detector irradiated by free electron laser pulses

Pikuz, T.; Faenov, A.*; 福田 祐仁; 神門 正城; Bolton, P.; Mitorfanov, A.*; Vinogradov, A.*; 永園 充*; 大橋 治彦*; 矢橋 牧名*; et al.

Optics Express (Internet), 20(4), p.3424 - 3433, 2012/02

 被引用回数:20 パーセンタイル:26.74(Optics)

Optical features of point defects photoluminescence in LiF crystals, irradiated by soft X-ray pulses of the Free Electron Laser were measured. We found that peak of photoluminescence spectra lies near of 530 nm. Our results suggest that redistribution of photoluminescence peak intensity from red to green part of the spectra is associated with a shortening of the applied for irradiation of LiF laser pulses down to pico - or femtosecond durations. Dependence of peak intensity of photoluminescence spectra from the soft X-ray irradiation fluence was measured and the absence of quenching phenomena, even at relatively high fluencies was found, which is very important for wide applications of LiF crystal X-ray imaging detectors.

論文

Observation of free-electron-laser-induced collective spontaneous emission (superfluorescence)

永園 充*; Harries, J.; 岩山 洋士*; 富樫 格*; 登野 健介*; 矢橋 牧名*; 仙波 泰徳*; 大橋 治彦*; 石川 哲也*; 繁政 英治*

Physical Review Letters, 107(19), p.193603_1 - 193603_5, 2011/11

 被引用回数:29 パーセンタイル:18.34(Physics, Multidisciplinary)

We have observed and characterized 501.6 nm collective spontaneous emission (superfluorescence) following 1$$s$$$$^2rightarrow$$1$$s$$3$$p$$ excitation of helium atoms by 53.7 nm free-electron laser radiation. Emitted pulse energies of up to 100 nJ ($$sim$$10$$^{{11}}$$ photons) are observed, corresponding to a photon number conversion efficiency of up to 10%. We observe the peak intensity to scale as $$rho^2$$, and the pulse width and delay with respect to the pump pulse to scale as $$rho^{-1}$$, where $$rho$$ is the atom number density. Emitted pulses as short as 1 ps are observed, which corresponds to a rate around 75000 times faster than the spontaneous 1$$s$$3$$p$$$$rightarrow$$1$$s$$2$$s$$ decay rate. To our knowledge this is the first observation of superfluorescence following pumping in the extreme ultraviolet wavelength region, and extension of the technique to the generation of EUV and X-ray superfluorescence pulses should be straightforward by using suitable atomic systems and pump wavelengths.

論文

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:67.52(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.

論文

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:19 パーセンタイル:30.15(Physics, Fluids & Plasmas)

極短パルス,極端紫外自由電子レーザー(EUV-FEL)パルス(波長:50nm,パルス幅:100fs)をフッ化リチウム(LiF)のような誘電体に照射することで、結晶状態にあるLiFの破砕現象を初めて観測した。低フルーエンスの場合ではLiFの破砕現象が起こり、これがLiFの低いアブレーション閾値の原因となっていることを明らかにした。同様の現象は、ピコ秒パルスの関西光科学研究所X線レーザー装置を用いた実験でも観測されている。この破砕現象は、ナノ秒パルスのX線レーザー装置では観測されておらず、フェムト$$sim$$ピコ秒パルス特有の現象であることをモデル計算から明らかにした。

口頭

フッ化リチウム(LiF)放射線検出器によるEUVFELの集光スポット計測

福田 祐仁; Faenov, A. Y.; Pikuz, T. A.*; 大橋 治彦*; 仙波 泰徳*; 永園 充*; 登野 健介*; 富樫 格*; 矢橋 牧名*; 石川 哲也*

no journal, , 

LiF放射線検出器を用いて、汎用集光システムによって集光された極端紫外自由電子レーザー(EUVFEL)の集光スポット形状の精密測定を行った。実験では、LiF放射線検出器を集光点付近に設置し、EUVFELをシングルショットで照射しながら、LiF放射線検出器をレーザービーム軸に沿って移動させた。レーザー照射によりLiF放射線検出器の表面にカラーセンターが生成し、集光スポット形状が記録される。測定の結果、スポット形状には収差による歪みが見られることが明らかになった。また、集光点(トランシット基準)よりも、上流側1mm付近に集光していた。また、集光スポットの中心付近ではLiF結晶のアブレーションが起こっていることを示唆するシグナルが得られた。

口頭

Observation and modeling ablation threshold features of dielectrics irradiated by ultrashort pulses of soft X-ray transient collisional and free electron lasers

Inogamov, N. A.*; Faenov, A. Y.; Pikuz, T.*; Zhakhovski, V.*; Skobelev, I.*; Khokhlov, V.*; Anisimov, S. I.*; Fortov, V. E.*; 福田 祐仁; 加藤 義章*; et al.

no journal, , 

The results of theoretical and experimental studies of ablation of LiF crystal by X-ray laser and FEL beams having photons with 89.3 eV and 20 eV with very short duration of pulse 7 ps and 300 fs are presented. It is found that the crater is formed for fluencies above the threshold Fabl about 10 mJ/cm$$^{2}$$: Such a small threshold is one order of magnitude less than the one obtained for X-ray ablation by longer (nanoseconds) pulses. The theory explains this dramatic difference as a change-over from more energy consuming evaporative ablation to spallative ablation, when the pulse duration decreases from ns to ps time ranges. We demonstrate that tensile stress created in dielectrics 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.

口頭

Low-threshold ablation of dielectrics irradiated by ultrashort pulses of soft X-ray transient collisional and free electron lasers; Observation and modeling

Faenov, A. Y.; Pikuz, T.*; Inogamov, N. A.*; Zhakhovski, V.*; Skobelev, I.*; Khokhlov, V.*; Anisimov, S. I.*; Fortov, V. E.*; 福田 祐仁; 加藤 義章*; et al.

no journal, , 

Theoretical and experimental studies of ablation of LiF crystal by X-ray laser and FEL beams were provided. It was found a very low ablation threshold for both types of irradiation. Such a small threshold is one order of magnitude less than the one obtained for X-ray ablation by longer (nanoseconds) pulses or 2 orders smaller than arradiated by fs visible pulses. The theory explains this dramatic difference as a change-over from more energy consuming evaporative ablation to spallative ablation, when the pulse duration decreases from ns to ps time ranges.

口頭

Multi-atom, multi-photon collective decay (superfluorescence) following EUV-FEL pumping of He

永園 充*; Harries, J.; 岩山 洋士*; 富樫 格*; 登野 健介*; 矢橋 牧名*; 仙波 泰徳*; 大橋 治彦*; 石川 哲也*; 繁政 英治*

no journal, , 

Superfluorescence is a collective, multi-atom, multi-photon decay process which can occur when a population inversion is created in a large number of atoms with sufficient number density. We create indirectly such an inversion on the helium 3p$$rightarrow$$2s transition by pumping using 53.7 nm EUV Free-electron laser (FEL) radiation at the SPring-8 Compact SASE Source (SCSS) test accelerator beamline, producing swept inversion in a 44 mm cube gas cell. Intense, highly-directional (divergence $$<$$ 20 mrad), linearly-polarised radiation at 501.7 nm is emitted in the direction of the incident beam. We have studied the characteristics of the emitted pulses using a streak camera and a calibrated photodiode.

口頭

Coherent spontaneous decay following multi-atom excitationwith FEL pulses; Prospects for X-ray superradiance from clusters

Harries, J.; 永園 充*; 岩山 洋士*; 富樫 格*; 登野 健介*; 矢橋 牧名*; 仙波 泰徳*; 大橋 治彦*; 石川 哲也*; 繁政 英治*

no journal, , 

Recently we have observed superfluorescence following 1s$$^2 rightarrow$$ 1s np excitation in helium using 100 fs pulses from the SPring-8 Compact SASE Source (SCSS) test accelerator beamline. One requirement for collective decay (as opposed to the competing natural decay and amplified spontaneous emission) is that the inter-atom spacing must be less than the wavelength of the emitted radiation. For visible radiation this is easily achievable in the gas phase, but for shorter wavelengths, clusters and other nano-scale particles present an ideal opportunity for observing and exploiting this mode of decay, which competes with all other decay mechanisms, including Auger. The potential for observing X-ray superradiance from multiphoton excited clusters has been described previously, but to our knowledge never been observed experimentally. We present details of our study in atomic helium gas, and discuss prospects for the extension to clusters and other nano-sized particles.

口頭

極紫外自由電子レーザー誘起による超蛍光の観測

永園 充*; Harries, J.; 岩山 洋士*; 登野 健介*; 富樫 格*; 仙波 泰徳*; 大橋 治彦*; 矢橋 牧名*; 石川 哲也*; 繁政 英治*

no journal, , 

実験はSCSS試験加速器施設で行われた。He原子を試料とし、SCSSからの極紫外自由電子レーザー(EUV-FEL)の波長を1s$$^2$$$$rightarrow$$1s3p共鳴励起相当に合わせ、高濃度のHe原子に照射し、その1s3p$$rightarrow$$1s2s脱励起過程に伴う蛍光(波長=501nm)の時間発展をガス濃度の関数としてストリークカメラにより計測した。He原子濃度が高くなるに従い、遅延時間が短くなり、パルス幅も狭くなっている様子が明確に見いだせた。観測結果の詳細な解析により、EUV-FEL光により励起されたHe原子が、原子集団として蛍光を放出する、超蛍光現象が起きていることが確認された。なお、半導体検出器による強度測定から、入射EUV-FEL光強度に対する超蛍光の変換効率は約10%と見積もられた。超蛍光の観測は、FELの利用研究としては現時点までで唯一のものである。EUV励起による超蛍光は、今回のような可視発光のみならず、1s3p$$rightarrow$$1s2脱励起によるEUV発光においても同様の振る舞いが観測されている。超蛍光は、特殊な環境下で起こる集団的発光現象であり、条件さえ整えば、XFEL励起によるX線超蛍光の観測も可能であると考えられる。SACLAの利用により、研究が大きく進展することが期待される。

口頭

The Near field and far field in situ characterization of soft X-ray laser beam by submicron-resolution LiF crystal X-ray detector

Faenov, A.*; Pikuz, T.; 福田 祐仁; 田中 桃子; 岸本 牧; 石野 雅彦; 錦野 将元; 神門 正城; 河内 哲哉; 永園 充*; et al.

no journal, , 

It was demonstrate high quality, single - shot in situ imaging of the near field and the far field intensity distribution of laser-driven transient-collision plasma and free electron soft X-ray lasers (SXRL) beams with 700 nm spatial resolution by color center formation in LiF crystals. The method based on diffraction of SXRL beams on the periodical structures and registration of diffracted patterns by LiF X-ray detector is proposed. It is demonstrated experimentally and by modeling that such approach allows measuring the intensity, coherence and spectral distribution of SXRL beam across the beam with high accuracy.

口頭

Superfluorescence observed following EUV-FEL excitation of helium gas

Harries, J.; 永園 充*; 岩山 洋士*; 富樫 格*; 登野 健介*; 矢橋 牧名*; 仙波 泰徳*; 大橋 治彦*; 石川 哲也*; 繁政 英治*

no journal, , 

We are currently witnessing rapid progress in the extension of effects now commonplace with visible light lasers towards shorter and shorter wavelengths. Highlights include XFEL-pumped lasing, and electromagnetically-induced transparency. Superfluorescence shares similarities with ASE lasing, but occurs only if several specific conditions are met. We have observed and characterised superfluorescence at a wavelength of 501.7 nm following 1s1s$$rightarrow$$1s3p excitation of helium atoms by 53.7 nm free-electron laser radiation. Emitted pulse energies of up to 100 nJ (10$$^{11}$$) photons were observed, corresponding to a photon number conversion efficiency of up to 10%. We observed the peak intensity to scale as $$rho^2$$, and the pulse width to scale as $$rho^{-1}$$, where $$rho$$ is the atom number density. Emitted pulses as short as 1 ps were observed.

口頭

The Interaction of SASE EUV-FEL pulses with high density atomic gas

永園 充*; Harries, J.; 岩山 洋士*; 富樫 格*; 登野 健介*; 矢橋 牧名*; 仙波 泰徳*; 大橋 治彦*; 田中 均*; 石川 哲也*; et al.

no journal, , 

Mirroring the development of research using optical wavelength lasers following their invention, we are currently witnessing rapid progress in studies of non-linear optical phenomena and applications at shorter and shorter wavelengths, as short wavelength FEL facilities reach maturity. Much of the recent work done at the Japanese SCSS test accelerator facility showcases non-linear phenomena. Here we present recent research exploiting the characteristics of the SCSS to observe superfluorescence, "Fano profile" wavelength filtering, and plasma up-conversion.

口頭

Characterizing the soft X-ray laser beams by submicron-resolution LiF detector

Pikuz, T.; Faenov, A.*; 福田 祐仁; 田中 桃子; 石野 雅彦; 長谷川 登; 錦野 将元; 大橋 治彦*; 矢橋 牧名*; 登野 健介*; et al.

no journal, , 

Review of results, obtained by using recently proposed new imaging detector, based on formation of color centers in LiF crystal and LiF film, for in situ high performance measurements of near-field and far-field properties of soft X-ray lasers (SXRL) beams is presented. Experiments have been carried out with laser-driven transient-collision plasma SXRL, free electron SXRL, and relativistic HOH beams. It was demonstrated that due to favorable combination of high spatial resolution, high dynamic range and wide field of view, that this technique allows measuring not only intensity distribution across the full beam and in local areas with resolution of $$sim$$ 700 nm, but also allows to evaluate coherence and spectral distribution of radiation across the beam. Experimental diffraction patterns in the images of periodical structures are analyzed by comparison with the modeled ones in the last case. Good agreement between experimental and modeling data was obtained.

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