Current Issue : October - December Volume : 2017 Issue Number : 4 Articles : 7 Articles
X-ray spectromicroscopy with a full-field imaging technique is a powerful method for chemical analysis of heterogeneous complex materials with a nano-scale spatial resolution. For imaging optics, an X-ray reflective optical system has excellent capabilities with highly efficient, achromatic, and long-working-distance properties. An advanced Kirkpatrickââ?¬â??Baez geometry that combines four independent mirrors with elliptic and hyperbolic shapes in both horizontal and vertical directions was developed for this purpose, although the complexity of the system has a limited applicable range. Here, we present an optical system consisting of two monolithic imaging mirrors. Elliptic and hyperbolic shapes were formed on a single substrate to achieve both high resolution and sufficient stability. The mirrors were finished with a ~1-nm shape accuracy using elastic emission machining. The performance was tested at SPring-8 with a photon energy of approximately 10ââ?¬â?°keV. We could clearly resolve 50-nm features in a Siemens star without chromatic aberration and with high stability over 20ââ?¬â?°h. We applied this system to X-ray absorption fine structure spectromicroscopy and identified elements and chemical states in specimens of zinc and tungsten micron-size particles....
Optical vortices, which carry orbital angular momentum (OAM), can be flexibly produced and\nmeasured with infrared and visible light. Their application is an important research topic for\nsuper-resolution imaging, optical communications and quantum optics. However, only a few\nmethods can produce OAM beams in the extreme ultraviolet (XUV) or X-ray, and controlling\nthe OAM on these beams remains challenging. Here we apply wave mixing to a tabletop\nhigh-harmonic source, as proposed in our previous work, and control the topological charge\n(OAM value) of XUV beams. Our technique enables us to produce first-order OAM beams\nwith the smallest possible central intensity null at XUV wavelengths. This work opens a route\nfor carrier-injected laser machining and lithography, which may reach nanometre or even\nangstrom resolution. Such a light source is also ideal for space communications, both in the\nclassical and quantum regimes....
We developed a single-shot X-ray spectrometer for wide-range high-resolution measurements\nof Self-Amplified Spontaneous Emission (SASE) X-ray Free Electron Laser (XFEL) pulses. The\nspectrometer consists of a multi-layer elliptical mirror for producing a large divergence of 22 mrad\naround 9070 eV and a silicon (553) analyzer crystal. We achieved a wide energy range of 55 eV with a\nfine spectral resolution of 80 meV, which enabled the observation of a whole SASE-XFEL spectrum\nwith fully-resolved spike structures. We found that a SASE-XFEL pulse has around 60 longitudinal\nmodes with a pulse duration of 7.7 �± 1.1 fs....
Due to their short wavelength, X-rays can in principle be focused down to a few nanometres\nand below. At the same time, it is this short wavelength that puts stringent requirements on\nX-ray optics and their metrology. Both are limited by today�s technology. In this work, we\npresent accurate at wavelength measurements of residual aberrations of a refractive X-ray\nlens using ptychography to manufacture a corrective phase plate. Together with the fitted\nphase plate the optics shows diffraction-limited performance, generating a nearly Gaussian\nbeam profile with a Strehl ratio above 0.8. This scheme can be applied to any other focusing\noptics, thus solving the X-ray optical problem at synchrotron radiation sources and X-ray freeelectron\nlasers....
The control of polarization state in soft and hard X-ray light is of crucial interest to\nprobe structural and symmetry properties of matter. Thanks to their Apple-II type undulators,\nthe FERMI-Free Electron Lasers are able to provide elliptical, circular or linearly polarized light\nwithin the extreme ultraviolet and soft X-ray range. In this paper, we report the characterization of\nthe polarization state of FERMI FEL-2 down to 5 nm. The results show a high degree of polarization\nof the FEL pulses, typically above 95%. The campaign of measurements was performed at the Low\nDensity Matter beamline using an electron Time-Of-Flight based polarimeter....
We present results of the studies of dynamics in colloidal crystals performed by pump-probe\nexperiments using an X-ray free-electron laser (XFEL). Colloidal crystals were pumped with an\ninfrared laser at a wavelength of 800 nm with varying power and probed by XFEL pulses at an energy\nof 8 keV with a time delay up to 1000 ps. The positions of the Bragg peaks, and their radial and\nazimuthal widths were analyzed as a function of the time delay. The spectral analysis of the data\ndid not reveal significant enhancement of frequencies expected in this experiment. This allowed us\nto conclude that the amplitude of vibrational modes excited in colloidal crystals was less than the\nsystematic error caused by the noise level....
Molecular dynamics is of fundamental interest in natural science research. The capability\nof investigating molecular dynamics is one of the various motivations for ultrafast optics. We present\nour investigation of photoionization and nuclear dynamics in methyl iodine (CH3I) molecule with\nan X-ray pump X-ray probe scheme. The pumpââ?¬â??probe experiment was realized with a two-mirror\nX-ray split and delay apparatus. Time-of-flight mass spectra at various pumpââ?¬â??probe delay times were\nrecorded to obtain the time profile for the creation of high charge states via sequential ionization and\nfor molecular dissociation. We observed high charge states of atomic iodine up to 29+, and visualized\nthe evolution of creating these high atomic ion charge states, including their population suppression\nand enhancement as the arrival time of the second X-ray pulse was varied. We also show the\nevolution of the kinetics of the high charge states upon the timing of their creation during the\nionization-dissociation coupled dynamics. We demonstrate the implementation of X-ray pumpââ?¬â??probe\nmethodology for investigating X-ray induced molecular dynamics with femtosecond temporal\nresolution. The results indicate the footprints of ionization that lead to high charge states, probing the\nlong-range potential curves of the high charge states....
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