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SYNCHROTRON-RADIATION RESEARCH
IN JAPAN: PREPARATION FOR SPring-8

NT

Groundbreaking for Japan's newest and largest synchrotron-radiation facility
took place in November 1991 at the future site of SPring-8 in Harima Science

Garden City, located in the mountains west of Kyoto. While the huge 8-GeV
storage ring and associated facilities are under construction, a series of annual

international symposia are being held to discuss candidates for the scientific
program to be undertaken after final commissioning of Spring-8 for research to
begin in 1998. The Third International Synchrotron-Radiation Symposium held

in Kobe, 18-19 March 1992, is reviewed here.

by Victor Rehn

INTRODUCTION
BACKGROUND

for research in a large number of fun

damental disciplines as well as for applied As construction of the $900M Over the past 10 years, synchrotron research in industry. Several other SPring-8 synchrotron-radiation (SR) radiation emitted by high-energy, high- storage rings have been built by private facility begins in earnest with a sched- current stored electron beams has proved industry in Japan for use (eventually) uled commissioning date for the begin- to be an extremely powerful tool for in developing x-ray lithography as a ning of user research on 1 April 1998, studying the structure of the matter production tool for semiconductor the Third Annual International and various physical and chemical devices. * Symposium on Synchrotron-Radiation processes. Japan's first electron stor- The need for a high-brilliance Facilities and Advanced Science and age ring dedicated as a synchrotron- synchrotron-radiation source that covers Technology was held in Kobe. This

radiation source was built in 1975 by the hard x-ray domain has been envisyear's symposium specialized in the use the Institute of Solid State Physics, aged among the scientific community. of SR in research in surface and inter- University of Tokyo, a 0.35-GeV ring. Japan's Council for Aeronautics, Elecface science. Twelve 45-minute papers Later a 0.66-GeV storage ring was put tronics, and Other Advanced Technolwere presented, each illustrating the into operation at the Electrotechnical ogy, part of the Science and Technolenormous potential of synchrotron- Laboratory in 1981, and a 2.5-GeVring ogy Agency (STA) of the Japanese radiation-based experimentation with at the Photon Factory, National Labo- Government, proposed construction of high-brightness, third-generation SR ratory for High Energy Physics, in 1982. a high-brilliance synchrotron light sources in studying the complex phys- In 1984 a 0.7-GeV storage ring was source in the report on “Policy for ics and chemistry of solid surfaces and built at the Institute of Molecular Sci- Promoting the Comprehensive interfaces. ence. All these facilities have been used Research and Development for Opto

Science and Technology” in July 1987

See, for example, the JTEC Panel Report on X-Ray Lithography in Japan, J.T. Clemens, Chairman (Loyola College in
Maryland, 1991).

** Note that the traditional optical term for electromagnetic intensity emitted by an extended source, normalized to unit

source area and unit solid angle of emission, is “brightness." However, due to some non-unanimity in the use of the term "brightness," many synchrotron-radiation scientists have now adopted the term “brilliance" for the same concept. In this article, the terms will be used interchangeably.

after extended discussions. It may be design work. Preliminary results of the scientists with X-ray sources of far higher noted that the U.S. Department of design effort as well as the R&D for brightness than any existing today. Energy commissioned a similar reportthe 6-GeV design were issued as the

the 6-GeV design were issued as the Conventionally, SR x rays are taken the Eisenberger-Knotek report on “The first draft of the Conceptual Design Report from the "bending magnets” which Need for New Synchrotron-Radiation (first edition) in May 1988.

determine the quasi-circular orbit of Facilities," in 1983, which reached In October 1988, JAERI and RIKEN the stored electrons (or positrons) in similar conclusions and led to the con- established a joint design team to sup- the storage ring. These magnets are of struction of two new “third-generation” port the construction of the facility. At relatively low magnetic field and proSR facilities: the Advanced Light Source this stage, the design energy of the storage vide a quasi-continuous spectrum of (ALS) in Berkeley, California, and the ring was raised to 8 GeV, and the two electromagnetic radiation (ER) from Advanced Photon Source (APS) at the institutes organized an Advisory Com

institutes organized an Advisory Com- infrared to x rays. The SR x-ray source Argonne National Laboratory in Illinois. mittee for the 8-GeV SR Facility Proj- brightness typically is four orders of

In June of 1987, STA convened an ect, chaired by Kazutake Kohra. Sub- magnitude greater than laboratory X-ray ad hoc committee to discuss the neces- committees on Accelerators (Kazuo sources. That was the thrill of the 1970s sity for the new-generation SR source Huke) and on Applications (Taizo for x-ray scientists. and to examine the requirements for Sasaki) were formed. In the Subcom- of the storage rings utilized for SR the new facility. The committee was mittee on Accelerators, the necessity sources in the 1970s, most were built chaired by Haruo Kuroda (recently of straight sections longer than the for high-energy physics. In these designs, retired from the University of Tokyo, regular 6.5-meter straight sections was care was taken to provide the narrowand now at the Tokyo University of strongly urged. The Advisory Commit- est possible beam only in the interacScience). The Kuroda committee estab- tee submitted two interim reports in tion regions where the high-energy lished that a high-energy storage ring August 1989 and in February 1990 experiments were carried out. The SR capable of providing highly brilliant concerning the basic configuration of beam lines utilized other parts of the synchrotron radiation (SR) in the x-ray the facility, its use, etc. In Figure 1, the orbit as source points, however, where spectral region was a high priority. Such organization of the SPring-8 project designers had minimized costs. a facility would promote a research team is shown. In the summer of 1989, Second-generation SR sources such and development (R&D) program in the nickname and logomark of the facility as the Photon Factory in Japan and the the fundamental disciplines such as phys- were determined by public suggestions National Synchrotron Light Source in ics, chemistry, biology, and materials to be “SPring-8” (Super Photon ring- the United States, were designed for science in the 1990s, according to the 8 GeV).

dedicated SR sources, and significant Kuroda committee. The importance of Harima Science Garden City in improvements in beam quality were the high-brilliance light source that Hyogo Prefecture was selected as the included. The SR x-ray source brightcovers vacuum ultraviolet (VUV) and construction site for SPring-8 in June ness was increased by another one to soft x-ray (SXR) domains was also noted. 1989. This new city has been under two orders of magnitude by introducThe energy of the storage ring was development since 1986 as a part of the ing high-field “wigglers” into the electentatively set to be 6 GeV. The Kuroda "Nishi-Harima Technopolis.” The site tron orbit. The wiggler provides sevcommittee stressed that research and has 141 hectares (348 acres) and is eral bends of the electron beam within development should be carried out in a located about 100 km to the west of the source region, thereby multiplying nationwide collaboration to overcome Osaka. The Faculty of Science, Himeji the source brightness. Use of higher the technical difficulties associated with Institute of Technology, opened in April magnetic fields in the wigglers also shifts low-emittance, high-brightness storage 1991. The grand site preparation was the spectrum toward harder x rays rings.

started in March 1990 by the Hyogo without requiring a higher electron beam RIKEN (the Institute of Physical Prefectural Government, who made the energy. and Chemical Research, an STA labo- site available to SPring-8 in April 1992. Third-generation storage rings use ratory) started the design study and Construction of a part of the storage “low-emittance” designs in which the R&D work on the low-emittance stor- ring building is underway at this time. transverse distributions of electron age ring in 1986. In the fall of 1987, The major purpose for building the position and momentum are minimized JAERI (the Japan Atomic Energy large “third-generation” SR sources all the way around the orbit, and long Research Institute, another STA orga- such as ESRF (European SR Facility), straight sections are included for insernization) joined with RIKEN in the APS, and SPring-8 is to provide research tion of wigglers and undulators.

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In the high-precision orbits of third- A 2-meter-long, 18-period, 1.5-T • “Surface Structure Determined by generation facilities, it is possible to wiggler source in SPring-8 will provide X-Ray Diffraction: Metal on Si(111) insert long, short-period, high-field quasi-continuum SR of high bright- Surface,” Toshio Takahashi, Instiundulators. Undulators cause the elec- ness up to photon energies of 800 keV. tute for Solid State Physics, Univertrons (or positrons) to undulate many The brightness of this wiggler will be as sity of Tokyo times as they pass through the source much as 1,000 times that of the 54-pole region, albeit with very low amplitude. wiggler installed at the Stanford • "X-Ray Standing Wave Atom LocaThe resulting undulator radiation (UR) Synchrotron-Radiation Laboratory tion and Thermal Vibration Amplihas a distinct, quasi-resonant, spiked several years ago.

tudes of Adsorbed Surface Atoms," spectrum; increased coherence; and

Jamshed R. Patel, AT&T Bell Labogreatly increased peak intensity. THE THIRD SYNCHROTRON- ratories

The third-generation high-energy RADIATION INTERNATIONAL storage ring with long, high-field undu- SYMPOSIUM ON

• “XAFS Studies of Molecular lator X-ray sources is now the highest SYNCHROTRON-RADIATION Adsorbates on Metal Surfaces," brightness source of soft and hard x rays FACILITIES AND ADVANCED Toshiaki Ohta, Hiroshima University by another one to fourorders of magni- SCIENCE AND TECHNOLOGY: tude over the wiggler sources. That SURFACE AND INTERFACE • “Photoelectron Scattering and makes the undulator X-ray source 9 to SCIENCE

Advanced Techniques in X-Ray 11 orders of magnitude brighter than

Photoelectron Spectroscopy with the once-powerful, rotating-anode, Opening Remarks and

Next-Generation Light Sources," laboratory x-ray sources. Needless to Facility Reviews

Brian P. Tonner, University of say, new scientific progress is easily

Wisconsin-Milwaukee visualized with the astounding X-ray The titles and authors of scientific brightness to become available with papers presented are as follows: • “Photoemission Spectroscopy of the commissioning of third-generation

GaAs Surfaces and Interfaces,” facilities. Also needless to say, there • “Status of APS,” David E. Moncton, Masaharu Oshima, NTT Interdisciare sure to be technological problems APS

plinary Research Laboratories in the design of beam lines and experimental apparatus for use with such highly • “Present Status of SPring-8 Proj- • "Surface and Thin Film Magnetism brilliant beams.

ect,” Hiromichi Kamitsubo, SPring-8 Studied by Spin-Resolved PhotoThe aim of the SPring-8 project is to Project Team

electron Spectroscopy," Jürgen promote the basic research and devel

Kirschner, Freie Universität, Berlin opment of advanced technology by using • “Surface Science and Synchrotron high-brilliance UR in the x-ray domain. Radiation," Akio Yoshimori, • “Perspective of Surface and InterThe facility will be opened equally to Okayama University of Science face Sciences," Yoshitada Murata, research groups of universities, national

Institute for Solid State Physics, laboratories, and industries.

• "Surface Structure at Electrochem- University of Tokyo The storage ring energy was deter- ical Interfaces," Ben Ocko, mined by the requirement for a funda- Brookhaven National Laboratory The opening address was given by mental UR X-ray photon energy up to

Minoru Oda, President of RIKEN and the K-absorption edge of element • "Time-Resolved X-Ray Studies of member of the Japan Academy. Prof. number 40 (Zr, K-alpha energy = Epitaxial Growth,” Paul H. Fuoss, Oda traced the earliest history of 18 keV). Preliminary suggested undu- AT&T Bell Laboratories

synchrotron-radiation science, beginlator designs with a 3-cm period, 4-meter

ning with war-time theoretical prediclength in the SPring-8 beam show the “X-Ray Diffraction Study of Fatty tion by J. Schwinger in 1943 and confundamental peak about 13 keV for Acid Monolayers at the Water Sur- tinuing with a discussion of the appliK=1.0. Harmonic UR will allow face,” Tadashi Matsushita, Photon cations to understanding the visible research with UR X-ray photon energy Factory, National Laboratory for and x-ray radiation from the Crab up to 40 keV or higher.

High Energy Physics

Nebula. Kazutake Kohra, Vice President, Japan Synchrotron-Radiation The current status of SPring-8 was surfaces to understand, especially in Research Institute, founder of the reviewed by Hiromichi Kamitsubo. He

reviewed by Hiromichi Kamitsubo. He process situations such as cleaning, Photon Factory and Chairman of the described the technical progress thor- epitaxial growth, metalization, passivaSPring-8 Project Advisory Committee, oughly. Great care is being given to tion, or etching. followed with a brief history of the minimizing thermal fluctuation and Ben Ocko of Brookhaven National Photon Factory and SPring-8. Kohra mechanical vibration. The Harima

mechanical vibration. The Harima Laboratory discussed the possibility also emphasized the international Science Garden City site is consider- for understanding of the electrochemical cooperation that has developed within ably more stable geologically than the

ably more stable geologically than the interfaces using angle-dependent x-ray the synchrotron-radiation community site of the Photon Factory, where realign- diffraction (XRD) and x-ray reflectivworld wide. Although the organizing ment following earthquakes has been ity for separating the surface layer from committee invited the directors of both required frequently. SPring-8 will be the underlying bulk. Interface layers ESRF in Grenoble, France, and APS built on bedrock, surrounding the top contribute only 10 of the bulk XRD in Argonne, Illinois, Kohra relayed the of a small mountain. At the Photon signal, so that high-intensity SR x rays regrets of Ruprecht Haensel of ESRF. Factory, 40-meter-deep support pilings are needed to obtain good interface Thus progress on the first of the three were used, which footed on an ancient data. X-ray reflectivity taken near a new giants of the SR world was not stream bed, not on bedrock.

core-level x-ray absorption edge of a presented at this symposium.

Following Kamitsubo's discussion known interface contaminant is very David Moncton reported, however, of progress, Moncton asked why sensitive to interfacial layers. that ESRF has recently achieved its SPring-8 will not open until 1998. The Ocko showed correlations of XRD first circulating current in its 6-GeV reply was that if funding were permissive, and x-ray absorption with cyclic storage ring, and commissioning by late SPring-8 could be finished 1 year early. voltametry in iodine layers on Au(111). 1993 or early 1994 seems probable. Reporters in the audience picked up

Reporters in the audience picked up Bias dependence of these electrochemCommissioning of the APS is sched- the possibility and reported it in the ical interfaces has been shown to influuled for the fall of 1996, and Moncton next day's newspaper as a fact. How- ence the surface atomic construction, foresees no major obstacles to achiev- ever, the approved funding profile is but the theory is understood only in a ing that schedule. At this time, the APS considered unchangeable. Sasaki stated general way from the general theory of construction project is on schedule and that the SPring-8 management team

Heine. under budget, Moncton reported with has no expectation that an early open- Paul Fuoss, AT&T Bell Labs, illusobvious pleasure. Total construction ing will be possible, although resched- trated beautifully the power of x-ray cost for the APS is estimated to be uling of various elements within the studies of epitaxial growth mechanisms. $465M, but adding research and devel- construction may be possible as long as In a collaboration with Kisker of IBM opment costs, early operating costs, the overall funding profile is not affected. and Brennan of the Stanford Synchroetc. brings the total cost to approxi

tron Radiation Laboratory (SSRL), all mately $800M between 1988 and 1996. Research Presentations three of the essential ingredients of the Moncton was asked several ques

organometallic vapor-phase epitaxy tions concerning project management. Following the theme started by Akio process were studied in the same How, for instance, would employment Yoshimori, most of the research papers chamber: x-ray spectroscopy of the of construction personnel be handled concerned the general problem of organometallic vapor and its fragmenat the completion of the project? How understanding the atomic and electronic tation, grazing-incidence XRD, and x-ray many staff members will be employed structure ofvarious types ofsurfaces or scattering of the growing surface and in beam line development? How will interfaces. Many presenters utilized one substrate. For example, a growth surface project scientists obtain beam time for of the several complex surfaces of sili- cut only 0.5o off the (100) Bragg plane their own experiments? How will the con, such as the Si(111) 7x7, or one of shows a splitting of the truncation rods workload of staff scientists be balanced the Si(100) surfaces as examples of the in x-ray scattering. Observing these between support of user scientists and power of synchrotron-radiation x-ray quantities in a time-resolved way personal research? What will be the experiments to determine surface struc- requires very high intensity x rays, Fuoss first experiment conducted on APS and tures. Both clean and “contaminated” declared. how is that decided?

surfaces were discussed as important

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