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Stuck in Neutron Neutral

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Science  23 May 2003:
Vol. 300, Issue 5623, pp. 1226-1227
DOI: 10.1126/science.300.5623.1226

As Japan and the United States gear up to build major new neutron sources, Europe's plans for a new facility have faltered

CAMBRIDGE, U.K., AND BERLIN—A decade ago, European neutron researchers were riding high. The world's two premier sources of neutrons were in Europe, plans were moving along for a new superfacility—the European Spallation Source (ESS)—and numerous national machines catered to a thriving community. Now, however, Europe's preeminence looks threatened: Some of the older national facilities are nearing the end of their working lives, and in a huge blow last year, ESS received a poor assessment from Germany's Science Council that crippled any chance to move that facility from the drawing board and into construction any time soon.

After having dominated neutron scattering for 2 decades, Europeans can only watch as the lead passes overseas. “The situation is going to become much less comfortable and more competitive compared to the U.S. and Japan,” says Bernhard Keimer of the Max Planck Institute for Solid State Research in Stuttgart, Germany. Adds Christian Vettier, science chief at the Institut Laue-Langevin (ILL) in Grenoble, France: “There is a risk that bright scientists will go to the U.S. and Japan. We need an exciting project to attract the best scientists.”

But the field's proponents have not managed to excite government funders. A neutron source can be as large and costly as a front-rank telescope or particle accelerator, but it won't find the universe's missing mass or discover the Higgs boson. Neutron scattering researchers do small science on big machines.

Neutron scattering “shows where atoms are and what they do,” says Robert Cywinski of the University of Leeds, U.K. Scientists shoot a beam of neutrons at a sample and register how the atoms deflect them. The x-ray photons produced by a synchrotron do essentially the same thing, but the two techniques are subtly different: Neutrons are electrically neutral, so they shoot through an atom's electron shells and ping off its nucleus. That makes neutrons much more sensitive than x-rays to hydrogen and water in biological samples, a key attribute for studying proteins and DNA. Pulsed neutrons can also provide a play-by-play as chemical reactions take place on a catalyst. And polarized neutrons—with all their spins, and hence magnetic fields, lined up—can follow magnetic excitations in a high-temperature superconductor.

For these and many other reasons, scientists from a range of disciplines—from structural biology and geology to materials science and engineering—flock to neutron sources. About two-thirds of the world's 6000 neutron researchers reside in Europe. They'll often run their experiments at a small national source, then book a couple of days at a facility like the ILL or the ISIS spallation machine near Oxford, currently the top two sources in the world. Sources come in two varieties: nuclear reactors, in which neutrons are a fission byproduct, and spallation sources, in which a particle accelerator fires a beam of high-energy protons into a dense metallic target, knocking out neutrons.

A turning point for neutron sources came in 1998 in the shape of a report from the Global Science Forum, a talking shop created by the Organisation for Economic Co-operation and Development (OECD) in Paris. It underlined the importance of neutron scattering for many areas of research and called upon governments to boost investment to make the most of current front-rank facilities, and for each of the major regions—North America, Europe, and Asia—to build a next-generation spallation source.

Room for expansion.

Upgrades at ISIS near Oxford will help keep Europe flush with neutrons, but researchers say this will only postpone their day of reckoning.

CREDIT: ISIS

In the United States and Japan, “the recommendations were taken on board and taken seriously,” says Cywinski. U.S. researchers had been starved of neutron sources for years and had suffered a major blow in 1995 when their great hope, the $2.8 billion Advanced Neutron Source, was killed off after a decade of planning (Science, 17 February 1995, p. 952). “The U.S. field was practically destroyed,” says Keimer. But by 1998, the U.S. community had pulled itself together and pushed through plans for a world beater, the Spallation Neutron Source at Oak Ridge National Laboratory in Tennessee (Science, 23 January 1998, p. 470). Japan, too, has joined the hunt; it's building a multiuse facility called J-PARC in Tokai that will include a spallation source. Both machines will begin operations within the next several years.

Europe was much slower to react to the OECD report. ILL set the ball rolling in 2001 by launching its Millennium Programme to upgrade its instruments and replace its 30-year-old neutron guides, pipes that channel neutrons from reactor to instruments. But Vettier says that ILL has had trouble persuading its funding states—France, Germany, and the United Kingdom—to fully support the $52 million project. They've given trifling amounts each year, amounting to just $10 million so far. “There is not a green light for completion,” Vettier says. The program suffered a further setback last year when French authorities assessed the reactor for seismic risk and called for major reinforcement work, improvements that will cost $24 million over 3 years.

The ISIS spallation source too has been pushing for extra investment. After researchers had campaigned hard for many years for a second target station—an addition that would roughly double the number of instruments but leave the accelerator unchanged—the U.K. government announced last month that it would come up with $162 million to complete the project.

Among smaller national sources, many are approaching retirement. Denmark's DR3 reactor at Risø closed in 2000, and other smaller reactors, such as Germany's FRJ-2 at Jülich, are likely to be shut down soon. In the meantime, a funding crisis across French research could doom the Orphée reactor in Saclay. “A decision [on its future] will no doubt be taken before the end of this year,” says Pierre Monceau, director of Saclay's Léon Brillouin Laboratory. Moreover, a recent report estimated that by 2020 half of all neutron-scattering instruments now in use in Europe will no longer be operational.

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One bright spot came last month when the German government finally gave the green light to FRM-II, a controversial reactor in Garching, near Munich. Approval to fire up the reactor, completed 2 years ago, had been held up by the environment ministry, which had opposed the reactor's use of highly enriched uranium fuel. Approval was granted on the condition that FRM-II convert to medium-enriched fuel by 2010. “This event will change everything,” says FRM-II's scientific director, Winfried Petry. “Our young people will come now that they see something that has a future.”

For many European neutron researchers, however, FRM-II and upgrades at ISIS and ILL will only enable them to live on borrowed time. “The community needs a vision,” says Michael Steiner, scientific director of the Hahn-Meitner Institute in Berlin. And that, he says, is “a big spallation-type source that will open up new possibilities.” ESS was to be the embodiment of that vision. Researchers behind ESS aired their latest plans to neutron users and government officials at a meeting in Bonn in May 2002. “It was a tremendously optimistic meeting,” says Cywinski. But in a move it may long regret, the ESS council submitted its plans to the German Science Council, as two German regions were bidding to host the facility.

Last July, after assessing ESS alongside eight other large-scale projects, the Science Council said it found the proposal unconvincing. In its view, the plans failed to demonstrate that the scientific questions that ESS would tackle could not be answered using other, cheaper techniques, such as synchrotron radiation, microscopy, optical spectroscopy, or computer simulation. Researchers were “incensed,” says Cywinski. Allegations soon emerged that the council ignored parts of the analysis from its own assessment panel for ESS. Later that month, Keimer and other panel members published a letter in Nature disputing the council's final conclusions: “[The council's] statement on the cost of neutrons relative to other techniques is not based on input from us and we do not believe it would be supported by a comprehensive analysis,” they wrote.

Several months later, ESS is still stuck in neutral. A panel on neutron sources, set up by the European Strategy Forum on Research Infrastructures (ESFRI), reported last January that ESS was the way to go but not in the near term. It recommended gearing up for the facility in 10 to 20 years.

Some think it would be foolish to slacken the pace. “Planning these big facilities takes a lot of time,” says Keimer. “We need a decision now to achieve it in the medium term,” says Cywinski. But with no pan-European mechanism for funding large facilities, he says, “there is no single doorstep on which to put your proposal.”

Some optimists do see a silver lining in the limbo that Europe finds itself in. “There will be some suffering and some will go to America or Japan, but when we use the time to create a really advanced source, then we'll be doing the right thing,” says Helmut Rauch of the Technical University of Vienna. Andrew Taylor, director of ISIS, points out that the U.S. Spallation Neutron Source is essentially an ESS design dating from the 1990s. “Wouldn't it be sensible to see how they do? Why compete? Let's work with them.” Thus with their long reign at the top coming to an end, European researchers face what for some is a humbling denouement: If you can't beat 'em, join 'em.

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