Photon Factory, long awaited by X-ray crystallographers, was commissioned three years ago and opened to general users two years ago. 26 stations are set up and more than 700 users are registered. Owing to the appearance of synchrotorn radiation, crystallography is entering upon the Renaissance. It is expected that many researches having great possibilities of development will be carried out. The ideas of such researches will be born rather often in Photon Factory itself where many researchers of different disciplines gather from various universties and laboratories of public agency and industry.

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Trace element determination by energy dispersive X-ray fluorescence analysis using synchrotron radiation is reported. Effects of excitation modes such as continuous or monochromatic excitation on the minimum detection limits are summarized. Trace element analysis in solution and the depth profiling of impurities in semiconductors are achieved by means of total reflection of X-rays. The minimum detection limits obtained are of the order of ppb or less than 0.1 pg. Applications to environmental and biomedical samples are also reported.

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Atoms with neibouring atomic numbers such as Pb and Bi cannot be distinguished with each other by the conventional X-ray. The crystal structure of lillianite (3PbS·Bi₂S₃) was determined by MoKα radiation, but the site occupancies in cation sites have been left unknown.
By means of synchrotron radiation applied to the structure analysis of the material using a four-circle diff ractometer set up at the BL-10A of the Photon Factory, the usual manner of refinement based on the data including anomalous dispersion effect of both atoms has been successfully performed with the result of site occupancies.

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A multi-anvil type X-ray system (MAX 80) installed at the Photon Factory is outlined. Remarkable advances in in-situ observation of crystal structure and phase transformation under high pressure and high temperature were obtained with the aid of the MAX 80 apparatus. Typical examples were demonstrated in the following topics : (a) Precise measurement of P-V-T relation of Au ; (b) Direct observation of the conversion reaction from graphite to diamond ; (c) Accurate determination of the olivine-spinel phase boundary in Fe₂SiO₄ ; and (d) Structure of the jadeite (NaAlSi₂O₆) melt and liquid Se at high pressure.

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Recent attempt at applying X-ray anomalous scattering phenomena to the study of local atomic arrangements in ternary metallic solid solutions are reviewed. Diffuse scattering intensity is measured over a volume of reciprocal space at the wavelengths near the absorption edges of constituent atoms using synchrotron radiation and is decomposed into partial intensities arising from different kinds of interatomic spatial correlations. In the region around the Bragg reflections, it is possible to separate the local order diffuse scattering from the pronounced temperature diffuse scattering.

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Characteristics of X-ray magnetic Bragg scattering are discussed. Synchrotron X-ray radiation is proved to be a suitable source for examining X-ray magnetic scattering by means of polarization analysis or resonance scattering. Some eminance in X-ray magnetic Bragg scattering is pointed out.

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The design features and performance of a newly-built multi-detector fluorescence-detected X-ray absorption spectrometer at the Photon Factory are described. Feasibility of fluorescence-detected X-ray absorption spectroscopy such as extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) for structural studies of very thin films is discussed. It is demonstrated that the local structure of thin films with a wide range of thickness from a few thousand Å down to a few tens of Å can be obtained. The ion beam-induced modification of thin nickel layers on Si (100) has been studied and the formation of amorphous Si-rich silicide as a result of ion bombardment is found.

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With an energy dispersive X-ray absorption spectrometer, the entire spectrum of interest can be recorded simultaneously. Hence, this method is suitable for timeresolved study of structural or chemical changes in materials which are not easily repeated hundreds or thousands times. We report a preliminary result of time-resolved (1.0 second resolution) X-ray absorption measurement with the energy dispersive spectrometer for reacting aqueous solutions of Fe (NO₃) ₃ and Na₂S₂O₃ mixed by a stopped-flow method. A time-dependent energy shift of Fe-K absorption edge was observed.

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At BL-15 A installed are a demagnif ying focusing optics and a time resolved X-ray detection system using a fast linear position sensitive detector, which make it possible to investigate dynamic atomic and/or molecular structure of materials. Some results of time resolved experiments of muscle during contraction and Al-Zn alloy during reversion are described.

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Described briefly are the present status of the experimental apparatus installed at the topography station and some user experimental results. At this station, it is possible to do the real time observation using VTR recording of topographic images of crystals either by direct method (saticon TV) or by indirect method (fluorescent film+TV) . Spot indexing of the Laue pattern and quick setting of the specimen orientation by computer has been developed. Many users have done various experiments since 1982 under various environmental conditions using white synchrotron radiation from normal bending magnet (BL-15) and wiggler magnet (BL-14) . Some examples of dynamic observations of the crystal imperfection, melting or solidification phenomenon, phase transition, and wall motion of the magnetic domain are shown.

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Motion of CDW in a quasi one-dimensional conductor K_0.30MoO₃ is observed by means of low-temperature X-ray diffraction. Time-resolving measurements reveal that moving CDW's are distorted in the transverse direction by the gradient of strength of the applied electric field in the sample. For pulsed fields the distortion reaches its steady state in about 1 ms at 77K.

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The synchrotron radiation X-ray diffraction study of the liquid-solid phase transition of the quasi-two-dimensional potassium layer in graphite intercalation compound is presented. Some critical properties show the behaviors of the continuous transition : (1) The wave number of the first in-plane diffraction peak, q₀, shows no discontinuous gap at the transition point. (2) The liquid layer has the same symmetry as the solid. (3) The intra- and interplane positional correlations of potassium atoms grow up in liquid state as approaching the critical point. However, the correlations show a discontinuous change at the transition. These results indicate that the transition is of the weakly first order. The phase transition can be understood in terms of the lattice-gas model.

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The 5-8 GeV new storage ring projects in Europe and USA are surveyed. Possibility of a project for a new intense source in Japan is also discussed.

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