An X-ray free electron laser, SACLA, started user operation in 2012. It is located adjacent to the 3rd generation synchrotron X-ray source, SPring-8. Current status of the facility is introduced in this article. With a high performance focusing optics, the laser light will be used to produce extremely high energy density state. The several fs wide X-ray pulses will reveal the ultrafast transient states during, for example, laser compression process.
Energy recovery linac (ERL) is a future X-ray light source designed based on the state-of-the-art low-emittance electron gun and superconducting linear accelerator technology, which realizes diffraction-limited beam in X-ray regime. The high repetition rate, short pulse, high spatial coherence and high brilliance of ERL will open a new era of photon science, which enables shooting ultrafast atomic-scale movies and structural determination of heterogeneous systems on the nanoscale. These unique capabilities of ERL drive forward a distinct paradigm shift in X-ray science from “static and homogeneous” systems to “dynamic and heterogeneous” systems. The expected beam performance and sciences of ERL are described.
Recent achievements and future challenges in mirror-based focusing devices for X-ray free electron laser are reviewed including a brief introduction of fabrication methods of highly accurate X-ray mirrors. KB (Kirkpatric-Baez) mirrors to focus the Japanese XFEL (X-ray free electron laser) down to 1 μm and sub-50 nm spot sizes, which have already been developed and installed into the XFEL facility, are discussed to reach the diffraction-limited focusing performances. Ultimately small spot size of sub-10 nm is now studied to be realized.
X-ray microscopy is one of promising candidates to non-destructively visualize internal structures in samples under extreme environments. We have developed a high-sensitive X-ray imaging microscope consisting of an objective lens and a transmission grating. The microscope is based on the Talbot effect of the grating and works simply by appending the grating to an X-ray imaging microscope. Our approach has several advantages over the Zernike X-ray phase-contrast microscopy that has been widely used, and can provide a powerful way of quantitative visualization with a high spatial resolution and a high sensitivity even for relatively thick samples.
Coherent X-ray diffractive imaging (CXDI) allows us to observe thick objects with a high spatial resolution, also providing us with unique structural information, i.e., electron density distribution and/or strain distribution. We have developed high-resolution diffractive imaging apparatus using the high-intensity X-ray beam focused by total reflection mirrors at SPring-8 and have demonstrated high-resolution plane-wave CXDI and scanning CXDI (i.e. X-ray ptychography). In addition, we have demonstrated element-specific X-ray ptychography using anomalous scattering around a specific element. In the near future, CXDI will become a promising tool for structure investigation in various fields including high-pressure science.
Application of coherent X-ray will be one of the main streams in the next generation synchrotron science. Many kinds of the methodologies have been established by using 3rd-generation synchrotron light sources. In this article, the author focuses on a so-called X-ray photon correlation spectroscopy (XPCS), and shows the recent advances in the application of XPCS to relaxor ferroelectrics.
The present status and future prospect of X-ray Raman scattering are discussed. X-ray Raman scattering is an effective tool to obtain information equivalent to soft X-ray absorption, under extreme conditions, such as high pressure. Several examples of high-pressure studies using X-ray Raman scattering are shown. In addition, experiments utilizing the momentum tunability on a single crystalline sample are suggested as a next challenge of high-pressure investigation. Furthermore, the future of X-ray Raman scattering utilizing further advanced synchrotron radiation sources is foreseen.
The nuclear resonant scattering and Mössbauer spectroscopy are going to be the experimental technique to investigate the element-specific electronic and vibrational properties in materials under multi-extreme conditions by using synchrotron radiation as an excitation source for a Mössbauer isotope. In this article, I introduced the basic principles of nuclear resonant scattering and Mössbauer spectroscopy and reviewed these current statuses in material science. Finally, I described future prospects of these methods using shorter-pulsed structure and higher-brilliance Xrays from new-generation synchrotron radiation facilities.