Figure 1. ETL budget distribution. Personnel expenses, totaling 51% of the budget, are subtracted before the above percentages are calculated. As part of the research in ultrafast sampling systems, an ultra-short-pulse laser system was developed. Using the colliding-pulse mode-lock concept, pulses less than 40 fs (= 4 x 10-14 s) (full width at half maximum intensity) have been produced. Using a sampling head consisting of a LiTaO, electro-optic crystal on GaAs substrate, the rise time of the sampling head was measured to be <1 ps (= 1 x 10-12 s). The measurement used a pump-probe arrangement of the laser beams. Measurements of the rise time versus propagation distance between pump and probe pulses were shown. Applications of electronic research methods to living systems were shown in two exhibits: • A computerized magnetoencephalographic recording system that records brain responses from 16,000 locations simultaneously. • A live-squid tank supporting studies of the giant axon in the super-simple nervous system of the squid. SYNCHROTRON-RADIATION SOURCE DEVELOPMENT In a recent review of synchrotronradiation (SR) sources worldwide, nine are listed as operational sources dedicated for x-ray lithography (Ref 3). Of these, eight are in Japan and one is at IBM, Fishkill, NY. Four of the Japanese sources are in Tsukuba Science City, two of which are at ETL. The 9 SR sources dedicated for x-ray lithography are in addition to 29 other SR sources in 12 countries, operational or under construction, that are utilized for research in many fields of science. Of the 29 research sources, 5 are in Japan. The Photon Factory (PF) is Japan's largest laboratory for SR research, largest laboratory for SR research, located in Tsukuba across town from ETL. The PF operates a large, 2.5-GeV storage ring as a national user facility, with 20 beam lines and 57 experiment stations covering the spectral range from infrared to hard x ray. In addition, the PF is utilizing the 6-GeV accelerator ring of the huge 30-GeV high-energyphysics electron storage ring, Tristan, where three beam lines with six experiment stations are available for users conducting experiments with very high conducting experiments with very high energy x rays. Within the research area of standards and measurement research, ETL has placed emphasis for the past dozen years on the development and utilization of SR sources for laboratory use. By contrast with PF, the storage rings at ETL are run for use by internal research staff (and their collaborators) only. A high-current 500-MeV electron linear accelerator, TELL, was placed in operation in 1980 (Ref 4). Currently, this source of high-energy electrons is utilized for injecting electrons into four storage rings, all of which are used for SR research. The largest and oldest, TERAS, is an 800-MeV ring completed in 1981. TERAS has been used for a variety of research on atomic, molecular, and solid state physics; optical devices; the formation of stratospheric particles; and lithographic technology research for ULSI (ultra-large-scale integration). It is instrumented with five beam lines and eight experimental stations, including a recently developed undulatingelectron-beam station that produces uniform large-area exposures for lithography. Another recent development is the arbitrary-polarization undulator, which produces SR with circular, elliptical, or linear polarization as needed by the experimenter (Ref 5). A visible-light free-electron laser (FEL) experiment uses a 1.5-mlong undulator. Both the spectral and temporal characteristics of visible FEL radiation have been reported recently (Ref 6). For angiography research and extended x-ray absorption fine structure (EXAFS) experiments, a new, very high field (10 T) superconductingmagnet, three-pole x-ray wiggler is being developed. Experiments on lengthening the stored-beam lifetime of storage rings have shown that vacuum-chamber outgassing using SR can significantly improve the lifetime. Beam lifetime is important in applications of x-ray lithography to manufacturing because it impacts the financial feasibility of the process. A collaboration with Sumitomo Electronic Industries (SEI) (a competitor of Sumitomo Heavy Industries in this field) was begun in 1985 for development of compact SR sources for laboratory use (x-ray lithography). The first of a series, NIJI-I, was installed at ETL in 1986 and replaced in 1989 by NIJI-II. (“Niji" is the Japanese word for "rainbow," an appropriate name for a broad-band SR source.) NIJI-II is a 600-MeV storage ring using four conventional bending magnets. It has two long, straight sections in which a 1.36-m-long undulator for chemical vapor deposition (CVD) research and a 1.30-m-long undulator with crossed and retarded magnetic fields have been installed. Recent studies of the characteristics of this uniquely controllable undulator have been presented, showing the comparison of theoretical and experimental absolute brightness in the 350- to 700-nm wavelength range (Ref 7). Another off-site storage ring is SORTEC, a 1-GeV storage ring built by the SORTEC Corporation with ETL collaboration in 1989. The SORTEC Corporation is a joint venture established in 1986 by the Japan Key Technology Center and 13 private industries. The SORTEC ring is a dedicated x-ray lithography facility, currently operating for users 8 hours per day, 4 days a week, with an average beam current of 185 mA, a 10-hour lifetime, and operation optimized for soft x-ray radiation of wavelength in the range of 0.7 to 1.3 nm. Four beam lines are currently available. It is planned that the beam current will be increased in mid-1992, thereby shortening exposure times and increasing the lithography wafers per day output possible. NIJI-III is the latest result of the collaboration with SEI. This is a 620 MeV storage ring that utilizes 4-T superconducting bending magnets in a compact design. Development of NIJI-III was sponsored by the Prime SR RESEARCH Minister's Science and Technology Agency through its Research and Development Corporation of Japan (JRDC). NIJI-III is a prototype development, being tested by ETL with the plan to return the ring to SEI for subsequent use in ULSI research and perhaps to lead to commercial production of compact storage rings. Currently, the commercial price of a NIJI-III type storage ring without beam lines is estimated to be about ¥2B ($15M), a very competitive price! The newest ETL rainbow is NIJI-IV, a 500-MeV conventional-magnet storage ring with two straight sections, over 7 m in length. This ring was built by Kawasaki Heavy Industries with very low emittance (design: 5 x 10 m-rad), as needed for ultraviolet and soft x-ray free-electron lasers. The low emittance is obtained using a magnetic lattice of the "triple-bend acromat" type, the same type used to achieve extremely low emittance in the new Advanced Light Source storage ring in Berkeley. NIJI-IV will be operated in single-bunch mode with stored current at least 20 mA for driving the free-electron laser. A variety of ETL research projects utilize SR in one way or another. The SR facilities are operated by a separate group, but the research of many divisions of ETL integrates SR techniques into its experimental program. A couple of examples of such projects are as follows: • One research group working mainly 0.6 0.4 A new method has been developed introduced into a molecular beam epitaxy system used for growing Si-Ge alloy crystals. Following the University of Tokyo's synchrotron orbital radiation (SOR) facility, ETL was the second laboratory in Japan to build and operate an SR facility for use by its internal research staff. The Institute for Molecular Science at Okazaki built Japan's third internal, integrated SR facility. The cost of operating and maintaining SR facilities has made it difficult for single institutions to support dedicated, internal SR facilities. In comparison, until recently only the National Institute of Standards and Technology (NIST) in the United States has operated its own internal SR facility. Now the University of Louisiana is in the process of establishing its own SR facility. Other SR facilities in the United States and elsewhere are mainly or mostly utilized as national user facilities, available to "any qualified scientist." In this case, the host organization accepts the responsibility for maintaining and operating the facility, but internal scientists must compete on an equal basis with outside scientists for "beam time." The ETL experience makes it clear that there are advantages to the dedicated, “internalonly" SR facility. New compact SR sources developed for ETL and elsewhere may make such SR facilities economically feasible in the future. REFERENCES 1. J. Itoh, S. Kanemaru, N. Nishimura, K. Tsuburaya, T. Watanabe, and S. Itoh, Technical Digest of IVMC 91, Nagahama (1991) (in English). 2. S. Kanemaru and J. Itoh, "Vacuum microelectronics," J. Inst. of Television Engineers of Japan 45(5) (May 1991) (in Japanese). |