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A beamline for the x-ray free electron laser (XFEL) of SPring-8 Angstrom Compact free electron LAser (SACLA) provides hard x-ray pulses in the range 4.5-19.5 keV. Its optical system in an optics hutch delivers a pink beam below 15 keV with either of two double-mirror systems or a monochromatic beam with a double-crystal monochromator. These XFEL beams are used for various types of measurement at experimental stations, e.g. x-ray diffraction, coherent diffraction imaging, x-ray spectroscopy and pump-andprobe measurement. The experimental stations consist of experimental hutches and control stations, and a femtosecond optical laser which is synchronized with XFEL pulses. Photon diagnostics have been performed for measuring radiation parameters in a shot-by-shot manner.

We report on the excellent performance of a newly constructed soft x-ray helical undulator beamline BL25SU of SPring-8 for photon energies 500-1800 eV. The full beamline was designed to perform very high resolution soft x-ray spectroscopy of solids with using high brilliance, highly circularly polarized undulator radiation. The grazing incidence monochromator employs varied-line-spacing plane gratings which operate in convergent light from a spherical mirror and focuses monochromatic light onto the exit slit. A resolving power in excess of 15 000 was measured at 540 and 870 eV for a grating with a central groove density of 600 lines/mm from the photoemission spectra of Au. A resolving power of more than 20 000 is estimated near 870 eV for a grating with a central groove density of 1000 lines/mm. A photon flux of more than 1ϫ10 11 photons/s/100 mA/0.02% b.w. is supplied onto the sample between 500 and 1800 eV with very low amount of higher-order light. The low heat load from the twin-helical undulator gives high stability to all optical components, which is essential to obtain high resolution in a wide energy region. Three experimental stations are installed in tandem on this beamline for various high resolution spectroscopy measurements.

A new soft X-ray beamline, BL07LSU, has been constructed at SPring-8 to perform advanced soft X-ray spectroscopy for materials science. The beamline is designed to achieve high energy resolution (E/ÁE> 10000) and high photon flux [>10 12 photons s À1 (0.01% bandwidth) À1 ] in the photon energy range 250-2000 eV with controllable polarization. To realise this state-of-the-art performance, a novel segmented cross undulator was developed and adopted as a light source. The details of the undulator light source and beamline monochromator design are described. The achieved performance of the beamline, such as the photon flux, energy resolution and the state of polarization, is reported.

Systematic investigation of the electronic phase separation on macroscopic scale is reported in the organic Mott system κ-(BEDT-TTF)2Cu[N(CN)2]Br. Real space imaging of the phase separation is obtained by means of scanning micro-region infrared spectroscopy using the synchrotron radiation. The phase separation appears near the Mott boundary and changes its metal-insulator fraction with the substitution ratio x in κ-[(h-BEDT-TTF)1−x(d-BEDT-TTF)x]2Cu[N(CN)2]Br, of which band width is controlled by the substitution ratio x between the hydrogenated BEDT-TTF molecule (h-BEDT-TTF) and the deuterated one (d-BEDT-TTF). The phase separation phenomenon observed in this class of organics is considered on the basis of the strongly correlated electronic phase diagram with the first order Mott transition.

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