X-ray harmonic comb from relativistic electron spikes

X-ray devices are far superior to optical ones for providing nanometre spatial and attosecond temporal resolutions. Such resolution is indispensable in biology, medicine, physics, material sciences, and their applications. A bright ultrafast coherent X-ray source is highly desirable, for example, for the diffractive imaging of individual large molecules, viruses, or cells. Here we demonstrate experimentally a new compact X-ray source involving high-order harmonics produced by a relativistic-irradiance femtosecond laser in a gas target. In our first implementation using a 9 Terawatt laser, coherent soft X-rays are emitted with a comb-like spectrum reaching the 'water window' range. The generation mechanism is robust being based on phenomena inherent in relativistic laser plasmas: self-focusing, nonlinear wave generation accompanied by electron density singularities, and collective radiation by a compact electric charge. The formation of singularities (electron density spikes) is described by the elegant mathematical catastrophe theory, which explains sudden changes in various complex systems, from physics to social sciences. The new X-ray source has advantageous scalings, as the maximum harmonic order is proportional to the cube of the laser amplitude enhanced by relativistic self-focusing in plasma. This allows straightforward extension of the coherent X-ray generation to the keV and tens of keV spectral regions. The implemented X-ray source is remarkably easily accessible: the requirements for the laser can be met in a university-scale laboratory, the gas jet is a replenishable debris-free target, and the harmonics emanate directly from the gas jet without additional devices. Our results open the way to a compact coherent ultrashort brilliant X-ray source with single shot and high-repetition rate capabilities, suitable for numerous applications and diagnostics in many research fields

Design of a high-resolution flat-field grating spectrometer for tender x-ray emission spectroscopy

高輝度化により次世代放射光施設での利用が期待されるテンダーＸ線領域の高分解能Ｘ線発光分光研究に供する平面結像回折格子分光器の開発を目的に、集光と分散（分光）を個々の光学素子が担うHettrick-Underwood型スリットレス平面結像Ｘ線分光器を設計し、その光学特性を光線追跡等のシミュレーションにより検討した。その結果、我々が従前開発した平面結像分光器（球面回折格子1枚で集光と分散を担う）に比して3倍超の高いエネルギー分解能を示すことが分かった。The 15th Symposium of Japanese Research Community on X-ray Imaging Optic

Chemical States Analysis of Trace-boron by using an Improved SEM-SXES

A soft X-ray emission spectroscopy-based electron microscopy, SXES-SEM, instrument used in combination with a micro-channel plate (MCP) detector and CMOS camera has been applied for analyzing the electronic state of bulk specimens. To improve the energy resolution of the system, the MCP with a channel pitch of 15 m has changed to a new one with that of 7.5 m. The L2,3 emission spectrum of Al from a bulk specimen was obtained by the improved system in photon counting mode. Taking into account of thermal broadening of the Fermi distribution function, we found that the energy resolution was improved up to 0.08 eV from 0.13 eV. Photon counting mode giving high energy resolution needs a longer acquisition time than analog integration mode. Thus, analog integration mode with a good signal to noise ratio but a few times lower energy resolution than photon counting mode was used to perform trace-boron analysis

Ultrahigh Energy Resolution RIXS Beamline at Next Generation 3 GeV Synchrotron Facility in Tohoku

次世代放射光施設で建設中の RIXS ビームラインの光学設計について発表する。14th International Conference on Synchrotron Radiation Instrumentatio

Design for nano-ARPES beamline at 3-GeV next-generation synchrotron radiation facility

次世代放射光施設で QST が第 1 期に整備される 3 本の共用ビームラインのうち、BL06U では軟 X 線ナノ光電子分光ビームラインとして、ナノ集光ビームを用いたスピン分解角度分解光電子分光（ARPES）を実現することを計画している。次世代放射光施設利用研究検討委員会ビームラインワーキンググループによって纏められた要求仕様に基づいて現在設計を進めているビームライン光学系について報告する。14th International Conference on Synchrotron Radiation Instrumentatio

Enhancement of diffraction efficiency of laminar-type diffraction gratings overcoated with diamond-like carbon (DLC) in soft x-ray region

Born is the critical trace element due to take the advantage of improving quenching characteristics in steel. Recently there is a great demand to detect the B-K emission band at around 6.76 nm more efficiently. To meet this demand we performed a feasibility study to enhance the diffraction efficiency of laminar-type diffraction grating based on a newly discovered physical phenomenon in the region of total reflection. The phenomenon is embodied as a transparent high-density material layer overcoated on a metal layer on grating grooves. The material should have intermediate diffractive index of vacuum and the metal layer. We found that high density diamond-like carbon (DLC) having a density of 3.1 g/cm3 is one of the best material and simulated the diffraction efficiency in a spectral region of 3.5-8.5 nm. The optimum thickness is 24 nm for an incidence angle of 87.0. Then the first order diffraction efficiency is expected to achieve up to 29.7 %, which is improved from 15.6 % for Ni or 14.1 % for Au, at 6.76 n