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4. OVERSEAS NEUTRON-SCATTERING FACILITIES RESEARCH REACTORS In this chapter we provide a selective~review of foreign neutron-scattering facilities, concentrating on instrumentation developments that have not been matched in the United States. Current activities in the modernization or expansion of facilities in Western Europe and Japan will also be summarized. Again much of our focus with respect to steady-state neutron sources will be on the rapid developments over the past decade at the Ins titut Laue-Langevin (ILL). It should be recalled, however, that much of the impetus for the European advances was work done at smaller centers, e.g., J6lich, Germany (SANS, backreflection spectrometry), Saclay, France (SANS), Munich (guide tubes). Another key to the European success has been the development and use of cold neutron sources and associated guide halls to create instruments for ultra-high-resolution and high-sensitivity spectroscopy (currently providing energy resolutions as much as 5 orders of magnitude better than available in the United States), small-angle and medium-resolution diffraction, and a variety of other new scientific applications (e.g., ultra-cold neutrons). These sources and related new instrumentation represent the major advances in neutron-scattering capabilities since the mid-1970s, and their development continues to grow in both Europe and Japan. At present, there is only one cold neutron source in the United States (at Broothaven National Laboratory) and one other is under development (at the National Bureau of Standards). Guide halls to improve the versatility 26

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27 and flexibility of cold or thermal neutron instruments currently do not exist in the United States. On the other hand, 60 percent of the neutron-scattering instruments at the ILL (16) are located in a large guide hall, and this fraction will rise when a new guide hall and cold source are completed over the next 2 years. In Table 2 we list the characteristics of neutron instruments at the ILL (mainly brought on-line since the mid-1970s) that either do not exist in the United States or have characteristics of intensity or resolution that significantly surpass comparable instruments in this country. A number of instruments with comparable characteristics also exist (and in fact were developed) at other European centers, e.g., JUlich (Germany), Saclay (Orphee) France. The summary in Table 2 does not reflect the entire picture of new capital investment and advanced instrumentation development in Europe. For example, major efforts in the development and construction of focusing monochromators, polarizing devices, reflecting supermirrors, environmental control systems, and dedicated instruments for diffraction surveys using neutron cameras attest to the continuing highly organized efforts to build new and more efficient instruments at steady-state sources in Europe. Moreover, currently under development at the ILL is an improved D2 cold source and a second D2 cold source that will serve six new instruments to be installed in a new guide hall by 1985. Further, there is a new reactor center (Orphee) at Saclay near Paris with two H2 cold sources that will ultimately commission 20 new instruments for neutron-scattering and fundamental physics research. An expanded guide hall with 9 new instruments

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30 is also under construction at the EFA Research Reactor in J6lich. Finally, the Japanese government has approved funding for the complete modernization of the JAERI III reactor at a cost of ~6150 million, including a replacement of the vessel, an upgraded fuel and beamrtube arrangement, and installation of a large cold source and guide hall. The total current operating expenditures for neutron scattering at research reactors in Western Europe is about 680 million/year (in fiscal year 1983 dollars) including associated reactor operation costs, roughly triple the O.S. effort. An order-of-magnitude difference emerges when one compares capital investment for new spectrometer development and construction efforts. Aside from recent new reactor construction (Saclay) and modification (Berlin), currently ~645 million worth of new or advanced neutron-scattering instruments and guide halls are either being commissioned or under development, primarily in France and West Germany but also in Sweden and Denmark. There is also a proposal for a major redevelopment of the Munich university research reactor to provide a new advanced center for neutron-scattering research. The consequences of this investment gap over the past decade between European and D.S. research reactors is being increasingly felt in our inability to compete in many areas of new science related to high-resolution neutron spectroscopy, small- and medium-angle diffraction, and diffuse scattering, for example. Further, the high degree of flexibility and efficiency afforded by the development of cold sources, guide-tube technology, and beam-focusing techniques has not been pursued in the United States. Fortunately, the major U.S. research reactors are still world class in terms

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31 of available thermal-neutron-beam intensities, and there are immediate opportunities to achieve a competitive status in advanced instrumentation for both cold and thermal neutron scattering, which will be outlined in Chapter 6. PULSED NEUTRON SOURCES The current U.S. position in pulsed neutron research and development is better in relative terms with respect to foreign competitors than is the case for steady-state sources. For example, the intense pulsed neutron source at Argonne National Laboratory is, for the present, the highest-intensity facility in the world, and the WNR/PSR is scheduled to provide by 1987 an order-of-magnitude increase in intensity for pulsed-neutron experiments. However, developments abroad make current comparisons highly misleading. For example, the SNS advanced spallation source under construction at the Rutherford Laboratory is scheduled to be brought on line by the end of 1984, with neutron intensities 2-3 times the current IPNS performance and will ultimately (by 1986) generate a current of 200 HA of 800-MeV protons on a spallation target, thus providing a peak thermal flux of 5 ~ 1015 neutrons/cm2-sec at a SO-Ez repetition rate, roughly twice the total intensity of the scheduled WNR/PSR source. This facility will ultimately have a complement of at least 15 neutron-scattering instruments, providing unmatched flexibility. Moreover, the Japanese, who have developed a modest-flux facility at TsuLuba with an impressive array of instruments, are also funding a planning and design study for a major new pulsed source (cost ~6100 million in fiscal year 1983

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32 dollars) that would slightly exceed the characteristics of the SNS. Perhaps of greatest potential impact on the long-term development of pulsed neutron sources, is the extensive study and design effort under way at the EFA in J6lich, West Germany. This major planning project with a budget of ~66 million/year is aimed at the possible ultimate construction of a pulsed spallation source with an ~1017 neutrons~cm2-sec peak flux and a time-averaged flux exceeding 1014 nentrons/cm2-sec. The potential cost of this facility (~6300 million to 6400 million capital, ~630 million/year operating) of course raises large scientific and political questions in the European community and will, at the very least, require a broad multidisciplinary base of support. The development of a source with these flux characteristics is perceived necessary by the German group in order to match or surpass the capabilities of modern high-flux reactors for low-energy neutron research and at the same time to exploit fully the new opportunities offered by pulsed sources, particularly for high-energy (>100-meV) neutron scattering. The study also includes a major effort to develop concepts and designs for a new generation of scattering instruments. Active efforts in new instrument designs are also a major part of ongoing activities at the Rutherford Laboratories ,~ Great Britain, in Japan, and at the Argonne National Laboratory (ANL) and the Los Alamos National Laboratory (LANL) pulsed sources. The two U.S. pulsed neutron efforts currently have a combined budget for source operations and

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33 scientific costs of about 610 million/year.2 While this mounts to about 40 percent of the total U.S. neutron-scattering unding, it still does not, for example, allow full-time operation of the IPNS source. In addition, this funding Level provides only marginal discretionary resources for the development of new instrument or source concepts. Again, Is for U.S. research reactors. there are important oppor- tunities for future pulsed-source development and research activities, which will be outlined in a later section. 2This figure assumes 62 million as the share of scientific and facility operating expenses provided at the WNR by the Office of Military Applications (OMA) of Department of Energy and discretionary LANL funds. The apportionment of funds provided by OMA for the development and scientific use of the WNR/PSR between nuclear or weapons-related research and materials-science applications is a complicating factor in the exact assessment of current neutron-scattering research funding but does not substantially affect the comparisons If U.S. and Western European funding included in this report.