A project called“The Photon Factory Project”is now being promoted by researchers of wide fields of natural science in Japan. In the Factory, synchrotron radiation ranging from vacuum ultraviolet to hard X-rays (10-105 eV) and high-energy γ-rays (several 109 eV) will be produced from an electron storage ring of 2.5 GeV and extensively utilized in various fields of study on matter of the atomic and nuclear level. Two kinds of working groups have been organized: users groups concerning diffraction, scattering, spectroscopy, analysis, radiation effects and high-energy physics and facility groups concerning accelerator, beam line, computer and common facilities. The project was recommended by the Japan Councile of Science to the government October 1974. The factory is scheduled to be built in an area adjacent to National Institute of HighEnergy Physics at Tsukuba, and is expected to be completed by spring 1980.
The properties of the synchrotron radiation are first discussed qualitatively and the main results of the exact theory are then summarized. The angular and spectral distributions of the synchrotron radiation from an electron storage ring now being planned in the Photon Factory are calculated. A layout of the beam lines and experimental areas coupled with the proposed machine is shown. Finally the photon flux of the proposed machine is compared with those obtained from other synchrotron radiation facilities.
Basic considerations and some specific topics on the design and construction of X-ray optical systems in the Photon Factory are given. Curved crystal monochromators used in appropriate optical geometry can collimate synchrotron radiation into small focus with an extremely high intensity. Multiple arrangements of plane perfect crystals in asymmetric diffraction are most useful in producing X-ray beams of various angular and wavelength spreads. Fluorescent secondary X-rays excited from metal targets by the synchrotron radiation are strong in intensity and free from high directivity and specific polariation.
The X-ray detectors of various types have been compared from the view-point of energy-, spatial- and time-resolutions. For some research subjects, the traditional detectors and methods are still useful. These examples have been pointed out. The possible improvements of these detectors have been discussed for meeting the major characteristics of SOR X-rays : the extremely high intensity, the pulse form of radiation and the tunability from continuous energy. In order to realize the real novel studies making the best use of the relevant source, the new detectors and experimental methods are needed, although the entirely new type of them cannot be figured out in a concrete form. Capability of each detector system should be made reasonably wide in order to meet various kinds of objects. This can favourably be realized by using interchangeable parts as far as possible.
The bottle-neck of the present energy-dispersive detectors is in the incompatibility between the counting loss due to the dead time and the energy-discriminating ability. This intrinsic neck should be improved as far as possible. From this point of view, scintillation-, proportional-counters and SSD are compared with each other, including their position-sensitive types. The bunching shape of the SOR source is also discussed from the above point of view.
Recent developments and the present state of art of the position sensitive proportional counters for X-ray diffraction are described. This kind of detector incorporated to a highspeed memory can provide very powerful means for rapid collection of diffraction data using synchrotron radiation. Briefly described are various methods for reading out impact locations of X-ray photons from multiwire proportional chamber detectors.
Television-type X-ray detectors are position sensitive detectors which permit rapid recording and readout of two-dimensional diffraction patterns wigh high spatial resolution. In Photon Factory, this kind of detector will be extensively used in in situ observation of X-ray topographs from single crystals under dynamic structural change. Strong intensity of synchrotron radiation will allow one to improve the spatial and time resolution of the detector and apply the method to studies on various transient phenomena. Another promising application of the detectors is to rapid acquisition of structure factor data from macro-molecular crystals. Incorporation of the detector to a fast digital memory device makes it possible to store the number of X-ray photons detected by each picture element at a television scanning rate. More than two order of magnitude higher data collection rate is expected over the standard diffractometer.
The on-line data processing systems in high energy physics laboratories in Japan, America and Europe are described. The computer system of these institutes is a complex system of central (large) computers and terminal (mini) computers. A terminal computer works mainly for data taking from detector and monitoring of data. Data taking is performed through a CAMAC system. CAMAC is explained shortly. The matter for preparation at a Photon Factory data processing system are also stated.
Fundamental problems of diffraction phenomena are briefly reviewed for two purposes ; a) an introduction to the following articles in this special issue and b) a desk research for the potential usef ullness of electron orbital radiations. Four topics are discussed. a) Problems regarding the new radiation source. b) Problems of the interaction between the radiations and matters. c) Some interesting diffraction phenomena which so far were unable to be experimentally studied. d) Diffraction phenomena under any specialised physical conditions.
The potentiality of synchrotron radiation for studies of X-ray optics is discussed. Besides a formidable high intensity source with continuous spectra, its very small angular divergence is very suitable for studying plane wave diffraction phenomena in nearly perfect crystals because the width of selective reflection for a perfect crystal is of the same order As topics are chosen studies using a highly parallel and monochromatic beam, X-ray interferometer, X-ray microscopy, X-ray lithography and X-ray holography. Emphasis is put on the first subject. The application of synchrotron radiation will bring about not only the shortening of experimental time but also the improvement of accuracy and development of new subjects in the field of X-ray optics.
Various kinds of inelastic scattering of X-rays have been classified from the viewpoint of their physical processes. For each kind of scattering, theoretical as well as experimental features have been described. They include Compton scattering, X-ray Raman scattering, plasmon scattering and X-ray Brillouin scattering. Then recent developements on EXAFS and anomalous scattering are also reviewed. The main features or promising results to be obtained by SOR X-rays are mentioned as far as possible in each relevant case in contrast to the corresponding features found with the conventional source.
X-ray topography has been shown by M. Hart (J. Appl. Cryst. 8, 436, (1975) ) to be one of the most successful applications of the synchrotron radiation. An example of experimental arrangements which will be convenient to share the X-ray beam guided in a guide tube for several topographic works, has been proposed. Wave length dependence on absorption by monochromatizing crystals and the spectral breadth of monochromatic rays has been discussed. Discussions given by M. Hart on resolutions on topographic images and on the effects of the overlapping of higher order reflections has been introduced. In future, high resolution fluorescent screens combined with optical cameras or cine cameras would be one of the standard techniques for recording the topographs.
The possible applications of the synchrotron orbit radiations with wave lengths of the order of 1Å in the field of dynamical structure analysis are discussed. In particular the‘real time’ analysis of the transient phenomena and various types of the irreversible processes taking advantage of pulsed X-ray source produced by the electron storage ring is examined from the experimental basis.
In this paper, it is discussed how to use X-rays obtained from SOR for the study of liquids, amorphous solids and gases on diffraction experiments. For example, the diffraction by using energy-dispersive detectors, small-angle scattering and relaxation of dipole orientation in the electric field of liquids are described considering that the beam is intense, polarized, pulsed and white.
A review is given on structural studies under abnormal conditions such as low and high temperatures, electric and magnetic fields, high pressure and so on. The advantage of energy-dispersive diffraction technique is discussed. Use of SOR is then shown to be very effective in these studies not only from its high intensity. The relative accuracy of lattice constants determined with the energy-dispersive method is expected to be 10-4 at best; this is much poorer than that obtained with the established angular-dispersive methods. Among these methods, the Bond method and the double-crystal diffraction method are examined in detail. The latter is superior to the former provided that incident X-ray intensities are much higher than those available at present. The lattice constant measurements with the combination of the double-crystal method and SOR will realize the accuracy of 10-7. Such measurements are important for the study of structural phase transitions and of influence of radiation damages on lattice constants; the latter will be a common problem in using SOR.
Recent advances in the high-pressure and high-temperature X-ray diffraction technique are generally reviewed with special reference to geophysical problems relating to phase changes and compression behaviour of the materials in the earth's interior. It is emphasized that the high-power X-ray source is extremely useful for the X-ray diffraction under very high pressure. Energy-dispersive type X-ray diffraction technique using the high-power polychromatic X-rays from SOR will improve the high-tempera-ture limit of the high-pressure X-ray study. SOR is hopefully applied to the X-ray diffraction study under deep mantle conditions, simultaneously to 200-1000 kbar and 1000-3000°C. An account is also given that SOR will be a powerful tool to investigate by diffraction, microcrystals or microtextures of minerals.
Despite its established powerfulness, the attempt to apply protein crystallography to a certain specific object is often hampered by various technical barriers which exhaust the individuals and the institution involved in the project. The availability of X-ray beam produced by synchrotron (orbit) radiation (SOR or SR) is expected to widen the horizon of protein crystallography in at least three ways. (1) The speed-up of data collection due to intensity will enable us to tackle larger proteins of more biological significance and, to some extent, to study the time-dependent phenomenon occurring in single crystals. (2) The better quality of diffraction data due to intensity and smaller divergence will liberate us from the burden of making very large crystals and will enable us to use lighter heavy atoms in the isomorphous replacement method. (3) The intrinsic variability of wave length of SOR X-ray coupled with the better quality of data will make the use of anomalous scattering effect much more feasible for the solution of the phase problem.
Contribution of the X-ray diffraction method to molecular physiology is going to increase markedly since the synchrotron orbital radiation (SOR) has appeared as a strong X-ray source. The photon factory project has brought us the following prospects. (1) It will become possible to study structural changes of biological systems during their functioning by use of the very strong SOR X-rays. (2) The S/N ratio of diffraction data will be improved by appropriate use of thestrong SOR X-rays of which the divergent angle is very small. (3) Studies of anomalous dispersion will become easy and more detailed information will be supplied to biological structures by using various wavelengths obtained from the continuous wide spectra of SOR X-rays. Recent technical developments in the X-ray optics, the position sensitive detectors and the X-ray televisions are paving the way to diffraction studies of dynamics of biological systems. Studies at the photon factory will be concerned with muscular contraction (time constant: -10 msec), biomembrane activities (time constant: -1 msec) and kin-etics of enzyme reaction (time constant: 1-100 msec) . A brief survey is made on some fundamentals and recent achievements concerning structural studies on contraction of muscle and on photoreception of retina.
Applications of SOR to the photoelecron spectroscopy, X-ray emission and absorption spectroscopies of solids are described. In particular, the possible advantages of using SOR as the source of stimulating radiation in photoelectron spectroscopy are discussed considering the high intensity of radiation and the tunability of photon energy.