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This study focused on the small concrete spalling caused by internal defects of time dependent behavior and investigated the relationship between spalling resistance and vibration properties using laser hammering system. By referring the laboratory test data, it was succeeded to detect for small spalling by using the raster scan measurement. In addition, the specimen’s vibration property data was simulated by the modelling of internal defect’s spalling resistance with spring constant. Finally, based on the verification of the issues and advancement of diagnostic by comparing human diagnostics method applying the existing tunnel lining, an effective way of implementing the laser hammering system was suggested.

We report the realization and characterization of parametric amplification in high harmonic generation around 100 eV using He gas in a double gas jet arrangement. The delay of the seed XUV pulse in respect to the amplifier gas jet was scanned by changing the distance between the gas jets. Experiments and numerical calculations show that parametric amplification occurs within a temporal window of several optical cycles. Strong correlation between the seed and amplifier was observed in a shorter, few optical cycles delay range, which appeared as a modulation of the XUV intensity with an unexpected one optical cycle periodicity instead of half optical cycle. Simulations revealed that the strong correlation and also the unusual periodicity was the consequence of the nonlinear effect produced by plasma dispersion on the parametric amplification process during propagation in the amplifier jet.

Irradiation effects of PMMA induced by femtosecond-pulsed extreme ultraviolet (EUV) were investigated using Soft X-ray free electron laser (SXFEL) for realization of next generation lithography. The sensitivity of PMMA upon exposure to femtosecond-pulsed SXFEL was much higher than that measured for conventional nanosecond-pulsed EUV source. This result speculates the reactions induced by femtosecond-pulsed SXFEL was different from those induced by nanosecond-pulsed EUV.

Currently, no evaluation method assesses intraoperative pedicle screw fixation (PSF) strength to determine the success of added support to a spinal fusion. Herein, we have established a laser-based resonance frequency analysis (RFA) system with high-speed, non-contact, quantitative measurements of PSF to evaluate implant fixation strength for future investigation of surgical failure risk of implants. We investigated the characteristics of the laser RFA by comparison with conventional methods. Pedicle screw was inserted in the vertebral pedicle of dissected human cadaver or artificial bone, followed by screw pull-out, peak torque, the implant stability quotient (ISQ) value obtained by magnetic dental RFA system and fixation strength of laser RFA. We compared outcomes using best-fit linear or logarithmic approximations. For the model bone study, the resonance frequency (RF) versus the conventional methods showed strong correlations (logarithmic: peak torque: R = 0.931, vs pull-out force (POF): R = 931, p < 0.001) and (liner: peak torque: R = 0.842, vs POF: R = 0.840, p < 0.001). RF strongly correlated with the ISQ value using linear approximation (R = 0.981, p < 0.001). For the cadaveric vertebrae study, the correlation coefficients between RF and the conventional methods were significant regardless of approximation method (peak torque: logarithmic: R = 0.716 vs linear: R = 811, p < 0.001) (POF: logarithmic: R = 0.644, vs linear: R = 548, p < 0.05). Thus, our findings revealed a constant correlation between RFA and the conventional methods, as a measurement validation, predicting its favorable support of intraoperative PSF.

Although laser irradiation with femtosecond pulses is known to generate crystallization and morphological changes, the contribution of optical parameters to material changes is still in discussion. Here, we compare two structures irradiated near Si–L2,3 edges by an extreme ultraviolet femtosecond pulse. Our result implies that, despite the femtosecond irradiation regime, these values of the optical attenuation length between the wavelengths of 10.3-nm and 13.5-nm differ by one order of magnitude. From the structural comparison, the original crystalline state was maintained upon irradiation at 13.5-nm, on the other hand, transition to an amorphous state occurred at 10.3-nm. The difference in optical attenuation length directly influence to the decision of material crystallization or morphological changes, even if the irradiation condition is under the femtosecond regime and same pulse duration. Our result reveals the contribution of optical attenuation length in ultrafast laser-induced structural change.

我々は軟Ｘ線レーザによる材料表面の加工学理の解明と、材料表面の直接加工への展開を目的とした研究を行っている。フェムト秒軟Ｘ線自由電子レーザーによるシリコンおよび石英の表面加工実験から、軟Ｘ線レーザの発振波長を材料に合わせて最適化させ、なおかつ集光径を十分に小さくできれば、熱的影響を受けた意図しない構造の無い無欠陥加工が実現できること、そして、軟Ｘ線レーザをナノメートルサイズに集光できれば、集光径と同等のナノメートルスケールのパターンの加工が可能となることの知見を得た。ここで得た成果は、超短パルス・短波長光源である軟Ｘ線レーザや高次高調波による表面微細加工の大きな可能性を示すものである。

There is no evaluation method currently available to assess intraoperative pedicle screw fixation (PSF) strength. In this study, we established a laser‐based resonance frequency analysis (RFA) system with high‐speed, noncontact, quantitative measurements of PSF. Clinical investigations in the future can assess surgical failure risk of implants. We investigated the characteristics of the laser RFA and compared them with the conventional methods. We inserted a pedicle screw in the vertebral pedicle of human cadaver or model bone, followed by screw pull‐out, peak torque, implant stability quotient (ISQ) value obtained by the magnetic dental RFA system, and fixation force of laser RFA. We compared the outcomes using best‐fit linear or logarithmic approximations. For the model bone study, the resonance frequency (RF) versus peak torque/pull‐out force (POF) demonstrated strong correlations using logarithmic approximation (vs. peak torque: R = 0.931, p

Parametric amplification of attosecond coherent pulses around 100 eV at the sin- gle–atom level is demonstrated for the first time by using the 3D time–dependent Schrödinger equation in high–harmonic generation processes from excited states of He+. We present the attosecond dynamics of the amplification process far from the ionization threshold and resolve the physics behind it. The amplification of a particular central photon energy requires the seed XUV pulses to be perfectly synchronized in time with the driving laser field for stimulated recombination to the He+ ground state and is only produced in a few specific laser cycles in agreement with the experimental measurements. Our simulations show that the amplified photon energy region can be controlled by varying the peak intensity of the laser field. Our results pave the way to the realization of compact attosecond pulse intense XUV lasers with broad applications.

フェムト秒レーザーアブレーションでは、固体中の電子と格子の衝突によるエネルギーの拡散時間よりもパルス幅が十分に短いため熱的な影響が従来の加工手法と比較して著しく小さくできる特徴がある。特にアブレーション閾値近傍では、表面にナノメートル級の微細構造が自発的に形成されることが広く知られており、新たな微細加工手法として期待されているが、微細・高速かつ長時間に渡る現象であるため、そのダイナミクスの実験的な理解は未だ十分ではない。本研究では、物質の表面状態の時間空間分解観測に最適な軟Ｘ線（波長13.9 nm(89 eV)）をプローブ光源とすることで、膨張する金属(Au)表面（Ablation Front: AF）及び表面から剥離した薄膜層（Spallation Shell: SS）の観測に成功し、アブレーションによりクレーターが形成されるまでの描像を明らかにした。本手法は、金属以外の様々な物質に対しても適用が可能であり、現在精力的に研究が進められている加工シミュレーターのベンチマークとしての役割が期待できる。

量研関西研では,レーザー駆動イオン加速機構によって生じる炭素ビームの横方向エミッタンスを明らかにすることに取り組んでいる。同時加速される陽子ビームから炭素ビームを弁別することが困難であるために，炭素ビームの横方向エミッタンスが評価された例はない。現在, 四重極磁石による核種の磁場弁別とダブルスリット法とを組み合わせた炭素ビーム横方向エミッタンス診断系の開発を進めている。 本発表では, 数理的な考えを診断装置に組み込むことによる, 観測誤差の低減に関して報告する予定である。, 第69回応用物理学会春季学術講演会

近年，炭素イオンなどを用いた重イオンビームによるガン治療は成功を収めている．一般的に，直線もしくはシンクロトロン型の粒子加速器が高エネルギー重イオンビーム生成のために使用されるが，それらの加速器は広く医療機関に行き渡らせるにはサイズが大きすぎるという問題を持つ．そのためコンパクトな加速器の実現が求められている．レーザー粒子加速器は，未来の加速器の候補の一つである． 量子科学技術研究開発機構では，高い治療効果が明らかになっている重イオンがん治療装置の高性能化・小型化を目指す“量子メス”プロジェクトを進めている．この次世代の小型重イオンがん治療装置は，重イオンビームの鋭いブラッグピークと，少ない内部散乱による腫瘍への高い線量集中性を持っている．これによって正常組織へのダメージを少なく抑え，より多くのがんを極めて短期間で治療できることが期待され、手術に代わる可能性を秘めている． 現在提案されている第５世代重イオンがん治療装置（量子メス）は，イオン入射器・超伝導シンクロトロン・ビーム輸送系・超伝導回転ガントリーから構成されている．装置を小型化するためには，体積の大部分を占める入射器とシンクロトロンの小型化が不可欠である．レーザー駆動イオン加速は非常に大きな加速勾配を持つことからこの小型化の要求に応える技術として期待されている．既存のイオン入射器をレーザー駆動方式で置き換えるためには，小型のレーザーモジュールの開発とそれを用いたレーザー駆動による数MeV/uの炭素イオンの加速が必要である．そこで，三次元電磁粒子コードによって実験に即したシミュレーションを実施することにより，加速炭素イオンの定量評価を行った．また，加速に有利な６価の炭素イオンを生成するためのレーザー条件を理論的に求め，シミュレーションによる妥当性評価を行った．, 日本物理学会第77回年次大会

Although laser irradiation with femtosecond pulses is known to generate crystallization and morphological changes, the contribution of optical parameters to material changes is still in discussion. Here, we compare two structures irradiated near Si–L2,3 edges by an extreme ultraviolet femtosecond pulse. Our result implies that, despite the femtosecond irradiation regime, these values of the optical attenuation length between the wavelengths of 10.3-nm and 13.5-nm differ by one order of magnitude. From the structural comparison, the original crystalline state was maintained upon irradiation at 13.5-nm, on the other hand, transition to an amorphous state occurred at 10.3-nm. The difference in optical attenuation length directly influence to the decision of material crystallization or morphological changes, even if the irradiation condition is under the femtosecond regime and same pulse duration. Our result reveals the contribution of optical attenuation length in ultrafast laser-induced structural change.

A counter-propagating laser-beam platform using a spherical plasma mirror was developed for the kilojoule-class petawatt LFEX laser. The temporal and spatial overlaps of the incoming and redirected beams were measured with an optical interferometer and an x-ray pinhole camera. The plasma mirror performance was evaluated by measuring fast electrons, ions, and neutrons generated in the counter-propagating laser interaction with a Cu-doped deuterated film on both sides. The reflectivity and peak intensity were estimated as ∼50% and ∼5 × 1018 W/cm2, respectively. The platform could enable studies of counter-streaming charged particles in high-energy-density plasmas for fundamental and inertial confinement fusion research.

Ultra-high intensities open a way towards Terawatt and potentially Petawatt gamma-ray pulses in the so called Gamma Flare regime. We performed our first experiment towards this regime with the J-KAREN-P laser operating at intensities close to 10^22 W/cm^2. In this presentation I will overview the experiment, including very bright hard x-ray generation (sub-MeV to a few-MeV spectral range), high-order harmonic generation (30 to 70 eV), and multiple additional diagnostics revealing information on preplasma (properties of reflected 1st, 2nd, and 3rd harmonics and back-reflection). I will compare these results with the integrated HD and PIC simulations., OPTO-2021 Symposium on Photon and Beam Science

We describe our experiment performed with the J-KAREN-P laser at the intensity approaching 10^22 W/cm^2. In particular, we present the results obtained with hard x-ray (0.1-3 MeV) spectrographs comprising 10 scintillators and a method to reconstruct the x-ray spectra., 3rd International Conference on Nuclear Photonics (NP2020)

At PW-class laser facilities pulse intensities of the order of 10^21 – 10^22 W/cm^2 can be reached by focusing high quality laser beams to spots of a few microns size. Under such conditions, during fs- time intervals a huge amount of optical energy is concentrated into a tiny volume and by the interaction with solid targets creates a plasma with high energy density. Such plasma can be sources of non-linear phenomena, among known and predicted by theory there is the acceleration to high energy of protons, ions, electrons and neutrons, generation of HOH and gamma-flare, creation of exotic states of hollow ions and WDM. The observed phenomena are defined by the type of target, laser energy and strongly depend on the prepulse condition. Achieving highly ionized states for elements with medium Z allows to effectively perform x-ray diagnostics of plasma parameters and preplasma conditions by means of high-resolution spectroscopy based on the analysis of spectra of H-like and He-like ions. Here we l present a review on the recent results on application of x-ray spectroscopic diagnostics of plasmas generated in the interaction of J-KAREN-P ultra-high intensity laser pulses with solid and clusters targets under conditions of different intrinsic laser contrast and under the cases of specially incorporated prepulse for controlled preplasma formation. Plasma parameters were evaluated by means of time integrated x-ray spectroscopic measurements and kinetic modeling using the code PrismSPECT. Certain line intensity relations, including the relations (Ly_a / He_b), (Ly_a / Ly_a satellites), relation between Ly_a satellites, as well as broadening and the shape of line, were used as the main tools for evaluation of plasma parameters. Each of the tools has preferred dependences on plasma electron temperature, electron density, electric and magnetic field strength. Four types of experiments are under consideration., 3rd International Conference on Nuclear Photonics NP2020

In situ femtosecond x-ray diffraction measurements and ab initio molecular dynamics simulations were performed to study the liquid structure of tantalum shock released from several hundred gigapascals (GPa) on the nanosecond timescale. The results show that the internal negative pressure applied to the liquid tantalum reached $\ensuremath{-}5.6\text{ }(0.8)\text{ }\text{ }\mathrm{GPa}$, suggesting the existence of a liquid-gas mixing state due to cavitation. This is the first direct evidence to prove the classical nucleation theory which predicts that liquids with high surface tension can support GPa regime tensile stress.

We present multi-diagnostic results from laser-plasma experiment at ~10^22 W/cm^2, including optical and high-order harmonics, back-reflection, soft x-rays, keV x-rays, and sub-MeV to MeV x-rays, simultaneously with important laser parameters. We discuss methods to find at-focus target position and compare intensity dependences., OPTICS & PHOTONICS International Congress 2021

After recent upgrade of the Petawatt-class J-KEREN-P laser system the experiments with on-target relativistic intensity up to 10^22 W/cm^2 (pulse energy ~10 J, pulse length ~40 fs, focal spot down to 1.5 um) are routinely carried out at KPSI, QST. In general, for solid targets the plasma formation threshold is of ~10^10-10^12 W/cm^2, therefore the long ASE prepulse, short and ultrashort pedestal intensity crucially impact the formation of plasma conditions and the observed phenomena. It was demonstrated that there exists a strong dependence of the degree of Fe ionization on a laser prepulse, and that an effective generation of energetic, multiply-charged moderate- and high-Z ions can be driven only with laser pulses of ultra-high contrast. Here we report on the new experiments performed at J-KAREN-P laser with the tailored plasma density profile created by specially incorporated prepulse. For the prepulse the ~1/100 of the main pulse power was picked up and delivered to the target with controlled sub-nanosecond time interval prior to the main pulse. The prepulse was focused: (1) on the front of a stainless steel foil for the formation of downstream preplasma with conditions aiming the efficient generation of x-ray flare and high-order harmonics (experiment led by A.S. Pirozhkov); and (2) on the rear-side of a 4-Chlorosterene foil mimicking upstream preplasma, which has the necessary density profile for collisionless shock ion acceleration, when the main pulse is irradiated (experiment led by Y. Fukuda and Y. Sakawa). For both experiments, we present the detailed analysis of plasma parameters provided by means of high-resolution x-ray spectroscopic methods, based on emission characteristics of plasma in the spectral range of Ne-like Fe and H-like Cl ionization states, respectively., International Conference on High Energy Density Sciences (HEDS2021)

量研・ 関西研では 、超電導シンクロトロンとレーザー駆動炭素インジェクターを組み合わせた重粒子線治療装置の量子メスの開発を進めている。この開発では、 TNSA 法 により、4MeV/ 核子の炭素を発生させ入射することを目標としているが、レーザー駆動加速イオンの特徴であるピコ秒領域の極短パルス大電流という炭素ビームが「ビーム輸送系を介して超伝導 シンクロトロン のアクセプタンスに入射できるのか」という点については十分な検討がされていない。そこで、ビーム診断系および輸送系コンポーネント（磁石、静電レンズ）通過時 に生じる磁場および電場（空間電荷効果以外の外力）による 非線形性の増大に関して計算できるように整備した。今回はそれらの 結果と、量子メス実験用プラットホームでペッパーポット式のエミッタンスモニタで求めた数十keV級低エネルギーのイオンビームのエミッタンス量の結果を比較検討したので報告する。, 日本物理学会第76回年次大会

Femtosecond-pulsed extreme ultraviolet (EUV) of free-electron laser (FEL) is the most potential candidates for a next-generation EUV lithography light source. However, the physical events and chemical reactions in resist materials, induced by EUV with a short pulse width and high power intensity, have not yet been elucidated. In our previous study, the morphological and chemical changes in poly(methyl methacrylate) (PMMA) induced by picosecond-pulsed EUV were investigated using an X-ray laser. The sensitivity of PMMA upon exposure to a 7 ps EUV pulse was much enhanced in comparison with that using conventional EUV sources, which have a typical pulse width of the order of nanoseconds. In this study, the sensitivity of PMMA upon exposure to femtosecond-pulsed EUV was investigated by using FEL to obtain the resist design for next-generation EUV lithography., 33rd International Microprocesses and Nanotechnology Conference (MNC 2020)

We evaluated laser-induced damage thresholds (LIDTs) on silica glasses by two kinds of ultra-short soft X-ray laser pulses (13.5 nm, 70 fs, and 13.9 nm, 7 ps). The comparison of our experimental results and the reported values observed by nanosecond soft X-ray pulse revealed a pulse width dependence of LIDTs on silica glasses in the soft X-ray region. The relationship between the pulse width and LIDTs provided valuable discussions of the laser-induced damage mechanism.

We investigated the charge-separated spectra of highly charged suprathermal bismuth (Bi) ions from a dual laser-produced plasma soft x-ray source developed for soft x-ray microscopy. The charge distribution of these suprathermal ions emitted from a solid planar Bi target was measured by an electrostatic energy analyzer. The maximum ionic charge state was observed to be Z = 17 and to possess a maximum energy of about 200 keV. This evaluation provides important information essential for the development of debris mitigation schemes in a soft x-ray microscope.

We have developed a soft x-ray laser (SXRL) beamline equipped with an intensity monitor dedicated to ablation study such as surface processing and damage formation. The SXRL beam having a wavelength of 13.9 nm, pulse width of 7 ps, and pulse energy of around 200 nJ is generated from Ag plasma mediums using an oscillator-amplifier configuration. The SXRL beam is focused onto the sample surface by the Mo/Si multilayer coated spherical mirror. To get the correct irradiation energy/fluence, an intensity monitor composed of a Mo/Si multilayer beam splitter and an x-ray charge-coupled device camera has been installed in the beamline. The Mo/Si multilayer beam splitter has a large polarization dependence in the reflectivity around the incident angle of 45°. However, by evaluating the relationship between reflectivity and transmittance of the beam splitter appropriately, the irradiation energy onto the sample surface can be derived from the energy acquired by the intensity monitor. This SXRL beamline is available to not only the ablation phenomena but also the performance evaluation of soft x-ray optics and resists.

Parametric amplification of attosecond coherent pulses around 100 eV at the single– atom level is demonstrated for the first time by using the 3D time–dependent Schrödinger equation in high–harmonic generation processes from excited states of He+. We present the attosecond dynamics of the amplification process far from the ionization threshold and resolve the physics behind it. The amplification of a particular central photon energy requires the seed XUV pulses to be perfectly synchronized in time with the driving laser field for stimulated recombination to the He+ ground state and is only produced in a few specific laser cycles in agreement with the experimental measurements. Our simulations show that the amplified photon energy region can be controlled by varying the peak intensity of the laser field. Our results pave the way to the realization of compact attosecond pulse intense XUV lasers with broad applications. Japan Society for the Promotion of Science (JP17H02813); Ministerio de Economía y Competitividad (FIS2017-85526-R)

Stability of orthopedic implant such as pedicle screw and acetabular cup is essential to prevent bone union failure. The subsequent complication is cause further surgery because of its aberration and looseness. A quantitative diagnosis approach which can be adaptable in surgery was developed resonance frequency analysis scheme based on laser induced vibration. As a principle of the diagnosis, a laser pulse irradiated onto the orthopedic implants to induce vibration, then the induced vibration was measured by acceleration sensor or laser Doppler vibrometer. The measured signal was analysed by fast Fourier transform method. In the case of the evaluation for acetabular cup which was set by press-fit, one of the peak frequencies of the induced vibration were increased with increasing an index of the stability defined by pull-down force as mechanical evaluation. The diagnosis scheme was considered for adaptation to surgery situation including usage for another implants and flexible handling. Optical multimode fiber and pedicle screw were used for validation. The stability diagnosis system was proposed as quantitative evaluation scheme adaptable in the surgery situation.

We present first principles calculations of parametric amplification of attosec-ond coherent pulses around 100 eV at the single-atom level in high order harmonic generation from excited states of He+ and compare them with experimental measurements. Our results indicate the basic physics to achieve the desired attosecond XUV gain in the spectral regions far from the ionization threshold of the considered interacting media.

We have developed an extreme ultraviolet (EUV) laser irradiation system at QST. EUV laser has a wavelength of 13.9 nm, and this laser wavelength is close to the wavelength of EUV lithography (λ = 13.5 nm). The irradiation system has an intensity monitor based on the Mo/Si multilayer beam splitter. This intensity monitor provides the irradiation energy onto the sample surface. So it is possible to examine and confirm damage/ablation thresholds of optical elements and doses for the sensitivity of resist materials, which have the same specifications of those in the EUV lithography.

In order to realize a compact and high repetition rate plasma X-ray laser, we have developed a recombination scheme plasma X-ray laser. In particular, we focused on a laser oscillation of Li-like aluminum 3d-4f transition (15.5 nm), which was already demonstrated in a high-density and low-temperature Al laser plasma with a low gain coefficient. In this study, by using an Nd:YAG laser (500 ps, 3 J, 16 pulse-trains) we created the lasing media and succeeded in laser oscillation at 15.5 nm. The optimization of the pulse-train in terms of the pulse duration and its interval enhanced the gain coefficient to g = 4.3 cm−1.

A new concept of integrated systems, named “IoT station”, using laser scan technology with visible laser diodes (LDs) common to smart lighting and LiDAR is proposed. It is applicable not only for smart lighting but also for image projection, power supply, and optical communications. As a fundamental verification of this system, a LiDAR using a LD emitting at red wavelength with two-axis scanning mechanism is fabricated for the first time. 3D image caption with detectable distance up to 10 m is achieved by the visible LiDAR. Spot lighting, projections, space signal transmissions and wireless power supply using light beam scanning are also verified as multi-purpose extended system. Additionally, spot lighting of which illumination area is controlled by visible LiDAR, has been successfully demonstrated.