The National Science Foundation's (NSF) Tokyo Office periodically receives and disseminates reports on research developments in Japan that are related to the Foundation's mission. Many of these reports are prepared by NSF-sponsored researchers currently working in Japan. These reports provide information for use by the global science and engineering community.
The following report was prepared by Dr. William A. Blanpied, Senior International Analyst in the Division of International Programs at the National Science Foundation. Dr. Blanpied visited Japan from October 14 - December 6, 1997 as a Visiting Research Fellow (short-term) under the sponsorship of the Japan Society for the Promotion of Science (JSPS). Professor Shinichi Yamamoto of the University of Tsukuba, Japan served as host scientist for Dr. Blanpied. Dr. Blanpied may be reached via email at: wblanpie@nsf.gov.
Japan's 8 Gev (billion electron volt) Super Photon ring (SPring-8) synchrotron radiation (or light) source was officially dedicated on October 6, 1997. Located in Harima Science City in Hyogo Prefecture, SPring-8 is the third of three roughly comparable third-generation synchrotron radiation facilities to be commissioned within the last three years, the other two being the European Synchrotron Radiation Facility (ESRF) in Grenoble, France, dedicated late in 1994, and the Advanced Photon Source (APS) at the Argonne National Laboratory near Chicago, dedicated in 1996. Construction of the facility began in 1991 and cost approximately $1 billion. Annual operating costs are estimated to be approximately $10 million. The SPring staff notes, with justifiable pride, that construction of the facility was completed a full year ahead of schedule.
The raison d'etre of any synchrotron radiation source is to produce intense beams of electromagnetic radiation - photons - which can be used for a variety of research purposes. The "third generation" designation used to distinguish the Harima, Grenoble, and Argonne facilities from earlier, existing synchrotron radiation sources indicates that they are designed to produce beams at much higher energies and, hence, much shorter wavelengths. SPring-8, for example, produces intense photon beams with energies ranging from somewhat less than a thousand to several hundred thousand electron volts; that is, from the soft to the very hard x-ray regions, whereas existing second generation sources produce photon beams primarily in the ultraviolet and soft x-ray regions.
The physics underlying all synchrotron radiation sources is fairly simple. High energy electrons (or, for that matter, any charged particles) confined in circular orbits (or "rings") emit electromagnetic radiation - photons - in sharply focused straight line paths tangential to their circular orbits, with the energy spectrum of the emitted radiation dependent on the energy of the orbiting electrons. In the case of SPring-8, electrons at energies of 8 billion electron volts are confined in a circular vacuum chamber approximately 230 meters (750 feet) in radius by a series of high-field electromagnets. Interspersed between these magnets are a series of radio-frequency cavities that maintain the stability of the orbiting electron beam by restoring the energy lost through photon emission. The assembly of magnets, radio- frequency cavities, together with the vacuum chamber containing the orbiting electrons, is known as a storage ring - literally, a ring for storing high energy electrons. Electrons confined in this storage ring attain their final energies in two stages: first, a linear accelerator (or LINAC) accelerates them to one billion electron volts, after which they are injected into a circular synchrotron which boosts their energy to eight billion electron volts and injects them into the final, 230 meter radius storage ring.
The SPring-8 electron storage ring has been constructed in such a way that maximum intensity x-rays will be emitted at 61 locations along the ring. The radiation emitted at each of these locations covers a broad energy or wavelength, with energies ranging from the soft to the very hard x-ray regions. In order to be useable for research purposes, x-rays in a narrow range of desired wavelengths must be separated from this broader emission spectrum and focused into narrow, parallel beams before impinging on the material target whose structural properties are to be investigated. Construction of an external beam line, which often includes auxiliary apparatus required for the type of experiments to be performed, is itself an expensive matter.
Four types of beam lines distinguished by their intended users are planned for SPring-8: (1) public beam lines whose construction is (or will be) financed by the facility itself and which will be available to Japanese and foreign scientists whose projects are approved by means of a peer review process overseen by an international advisory committee; (2) contract beam lines, financed by approved external organizations and reserved for their exclusive use; (3) beam lines reserved for use by RIKEN (the Institute for Physical and Chemical Research) and JAERI (Japan Atomic Energy Research Institute), the co-funders of SPring-8, and (4) four beamlines where research on the characteristics of the synchrotron and beamlines themselves will be carried out with a view toward upgrading and improving the facility itself.
Plans call for the eventual construction of 20 public beamlines. Five of these are already in operation, with an additional five scheduled for completion by the end of 1997. Osaka University and a consortium of Japanese industrial firms are constructing the first approved contract beam lines. SPring-8's management anticipates foreign involvement in the construction and use of some of the public and, perhaps, some of the contract beam lines as well.
The x-rays produced at SPring-8 have wavelengths characteristic of the interatomic to the intermolecular dimensions of matter in its condensed state. These beams are thus an ideal tool for probing the microstructure of matter by, in effect, photographing the atomic and molecular structure of a wide variety of materials. Public beam lines at the facility differ in the wavelengths of the x-ray beams provided and, thus, in the types of experiments for which they are intended. Among the first being prepared for use are those intended for the soft x-ray spectroscopy of solids, soft x-ray photochemistry, protein crystallography, high-energy inelastic scattering, and nuclear resonance scattering. One public beam line will have auxiliary apparatus permitting structural analysis of matter under extremely high pressures; another will permit similar studies at extremely high temperatures.
X-rays are emitted from the SPring-8 storage ring in very short bursts, giving their constituent photons a high degree of temporal coherence. Likewise, synchrotron radiation itself has a high degree of spatial coherence. These characteristics make it possible, in principle, to conduct basic research on fundamental quantum mechanical properties of photons, provided that sufficiently long beam lines are available. Additionally, a sufficiently long beam line would permit research on the gravitational properties of photons. The construction and siting of the storage ring makes it possible to construct up to three one kilometer-long beam lines. These, however, would be very expensive to construct and would require highly specialized and sensitive ancillary experimental apparatus. For these reasons, according to facility management, their construction and operation will require international cost sharing.
Although third-generation synchrotron radiation sources certainly qualify as large-scale scientific facilities, they differ in several important respects from particle accelerators - up to now regarded as the prototypical large-scale facility - based on the uses for which they are intended. Particle accelerators accommodate very few experimental groups at any one time. On the other hand, these groups are very large, often consisting of several hundred scientists in addition to numerous technicians. The auxiliary experimental apparatus they require and for whose construction costs they themselves are primarily responsible is typically large, complex, and expensive.
In short, particle accelerators are large-scale facilities intended for a small number of very large-scale research projects conducted mainly by scientists in a single discipline - namely, particle physics.
Contrastingly, third generation synchrotron radiation sources are designed to accommodate a large number of users at any one time, limited only by the number of operating beam lines. These user groups are typically small and conduct small-scale experiments that normally do not require them to bring in a great deal of additional apparatus. Importantly, user groups come from a range of scientific disciplines - physics, chemistry, and biology, for example - and include both university users conducting basic research and industrial users conducting applied research.
Therefore, to differentiate them from particle accelerators, third-generation synchrotron radiation sources are large-scale facilities intended for a large number of small-scale research projects conducted by scientists from a wide range of disciplines.
The times required for experiments at particle accelerators range from several months to well over a year. In contrast, SPring-8's management anticipates that the average duration of experiments conducted at the facility will be approximately two weeks.
Funding for the construction and operation of SPring-8 is shared by the Institute of Physical and Chemical Research (RIKEN) and the Japan Atomic Energy Research Institute (JAERI). It is extremely rare, perhaps unprecedented, for two Japanese organizations to share support for a research facility.
In October 1997, responsibility for the operation, maintenance and improvement of the facility was transferred to the newly created Japan Synchrotron Radiation Research Institute (JASRI), a semi-autonomous organization fully funded by RIKEN and JAERI.
The SPring-8 Users Society, open to membership from all qualified research institutions, both Japanese and foreign, was established in 1993. Representatives from this users society are responsible, for example, for advising facility management on the detailed design of the public beam lines and for overseeing and monitoring the peer review of research proposals for use of the public beamlines. Universities constitute 67 percent of its current membership, Japanese public research facilities 16 percent, and industrial firms the remaining 17 percent.
Hyogo Prefecture, in which SPring-8 is located, is constructing a second- generation, 1.5 billion electron volt synchrotron radiation source near the site of the principal 8 Gev storage ring and its auxiliary beam lines. This facility is intended for use by the Industrial Technology Laboratory of the Himeji Institute of Technology, whose main campus is approximately an hour's driving time from SPring-8.
A new Structural Biology Facility is also being constructed on site by RIKEN. Ample space is available for construction of additional, related facilities in the future - by JAERI, for example, should any such facilities come to be regarded as feasible and appropriate at some future date.
It is the policy of SPring-8 to provide access to public beam lines free of charge to qualified users, both Japanese and foreign, whose research projects are approved by a peer review committee, including industrial users who intend to publish their research results in the open scientific literature. This access policy is analogous to that employed by the European Synchrotron Radiation Facility (ESFR) and the Advanced Photon Source (APS), the two other third-generation synchrotron radiation sources. Both ESFR and APS have attracted considerable interest by foreign user groups, and there is no reason to expect that SPring-8 will differ in this respect.
The facility management, however, anticipates more substantial international cooperation, in addition to providing access to qualified foreign users. Although SPring-8 is now fully operational in the sense that it is capable of providing high quality x-ray beams for a wide variety of research projects, the facility has yet to be optimized. That is, a number of changes - some relatively minor, some substantial - could be made to improve the efficiency as well as the energy and quality of the x-ray beams produced by the facility. Details of some of these changes have already been worked out; others could require considerable research before being implemented. In fact, it is common practice at large-scale facilities throughout the world to make them available to users before they are fully optimized, reflecting the fact that such facilities are normally designed with the expectation that if they are to remain attractive to potential users for 20 years or more, they will require continuing improvements and upgrades. Such improvements and upgrades require, in turn, substantial research related to the design and operation of the facilities themselves.
As a case in point, the third-generation synchrotron radiation sources at Grenoble and Argonne were also made available to users prior to being optimized, and both also anticipate making improvements and upgrades during the next few years. Because of the similarity in the research problems that need to be addressed, ESFR, APS and SPring-8 have concluded a formal, tri-lateral cooperative agreement to plan and conduct, in common, as much of this design-based research as may be appropriate and feasible. An early priority will be to address the problem of thermal loading. The intense x-ray beams produced by all three of these facilities create a great deal of heat when they impinge on experimental research targets. In fact, the heat generated is so great that it currently precludes any of these facilities from operating at their maximum design intensity. Determining ways to dissipate the heat generated by the x-ray beams more effectively would permit more efficient operation and, in some cases, even make possible types of experiments that are not considered feasible at present.
SPring-8 management also hopes for substantial international involvement in the design and construction of beam lines. As noted earlier, the design and siting of the storage ring can accommodate up to three one-kilometer beam lines that could be used to study fundamental properties of photons. However, the expense involved in constructing such beam lines and developing the necessary auxiliary research apparatus would require international cost sharing at some level.
As to future contract beam lines, SPring-8 management believes it has a special obligation to assist East-Asian countries to develop and make effective use of their own beam lines. While it recognizes that both financial and technical assistance would normally be required, detailed plans for providing such assistance have yet to be developed. However, such a program would be consistent with one of the principal objectives of the Government of Japan's July 1996 Basic Science and Technology Plan to actively assist developing countries in the Asia-Pacific region to become more closely integrated into the international scientific community.
Meanwhile, serious negotiations are underway with the Bhabha Atomic Research Center in Trombay, India (near Bombay), that could lead to a contract beam line financed completely by the Government of India. One significant issue that has yet to be resolved is how much of the requisite beam line technology and hardware would be produced in India and how much will be produced in Japan.
SPring-8, located in Hyogo Prefecture, is located approximately 100 kilometers west of Osaka and approximately 500 kilometers south of Tokyo. Himeji, the nearest sizable city and an hour by car or taxi from the facility, can be reached by train from Kansai International Airport, Osaka, in about 90 minutes, or from Narita International Airport, Tokyo, in about four and a half hours. The nearest railway station to SPring-8 is Aioi, a half-hour trip by car. However, fewer fast trains stop at this station than at Himeji.
Guest facilities for researchers are available on-site, including a cafeteria and a dormitory which currently has 60 rooms available and which, when completed, will have 180.
For more information about SPring-8, including highlights of procedures
for submitting proposals for use of the public beam lines, visit the facility's
homepage: http:/www.spring8.or.jp