Scientists in Europe face a dramatic reduction in neutrons beams for research within the next 5 to 10 years, even though the world's most intense neutron source is expected to turn on in Sweden by the end of the decade. So says a panel of experts commissioned to assess the imminent closure of many of the continent's aging neutron reactors and recommend what can be done to avoid or at least reduce the shortfall.

The panel, known as the Neutron Landscape Group (NLG), published its findings in an updated roadmap released last week by the European Strategy Forum on Research Infrastructures, which reports to the Council of the European Union. The roadmap, first published in 2006, provides a rolling list of proposed pan-European research facilities deemed to be both excellent scientifically and that already have financial backing from one or more E.U. member states.

The 2016 roadmap features 21 projects, five of which are new additions since the 2010 edition: facilities studying the atmosphere, river-sea systems, and food security, as well as a solar telescope and a new center for cultural heritage. A sixth project, a neutrino telescope to be built at the bottom of the Mediterranean Sea known as KM3NeT, has re-entered the roadmap after being included originally in 2006 as a single observatory before being split between sites off Italy and France.

The neutron review comes as part of a wider "landscape analysis" carried out for the roadmap that seeks to identify significant gaps or overlap within European research infrastructure. NLG, chaired by physicists Colin Carlile of Uppsala University in Sweden and Caterina Petrillo of the University of Perugia in Italy, points out that more than 6000 scientists and engineers in Europe use neutrons to study the structure and behavior of materials, which range from magnets and superconductors to plastics and proteins. However, it says, two-thirds of the continent's operating neutron sources were built in the 1960s and 70s, and most of those are due to close in the next decade.

The European Spallation Source (ESS), which is being built in Lund, Sweden, and will use a proton accelerator to generate the world's most powerful beams of neutrons, is due to start operating in 2019. However, explains NLG, limited initial funding means that the facility will have just 16 instruments up and running by 2028, which, it says, will leave researchers considerably worse off than they are today with the 40 instruments that make up the currently operating Institut Laue-Langevin (ILL) in Grenoble, France.

But the convention signed by the three countries that operate the ILL—France, Germany, and the United Kingdom—is due to expire in 2023. A closure at that point, combined with the closures of other, less intense neutron sources in Europe within the next few years, according to the panel, would cut neutrons available for research by between 40% and 50% over the next 15 years—the exact timing of the drop depending on the ILL's power output and how many other facilities are switched off.

Carlile says that this reduction would not only be devastating for current scientific research, but would also make it much harder for younger researchers to gain experience of making neutron-based measurements. "People who use these facilities have no stepping stone to get there," he says, "unlike users of x-ray sources, which are available at universities."

According to the panel, neutron output over the next 15 years could be kept to within 20% of existing levels so long as the ILL and the other neutron sources that risk closure operate until at least 2030. These extensions, estimates Carlile, would cost about €200 million, which, he adds, is "not peanuts" but is considerably less than is needed to build a major new facility such as the ESS. However, it remains to be seen, he says, whether the owners of the ILL will want to extend the life of what will then be a more than 50-year-old nuclear reactor in a city where space is very much at a premium. "The closure of the ILL will have a traumatic effect on the neutron community," he says. "But none of the owners or users want to talk about it in public."

Carlile is also concerned that the ESS won't reach its full power of 5 megawatts (MW) as it is scheduled to do in 2025. "I am quite confident that the project can deliver on time, provided it is properly supported politically," he says. "But the one thing I fear is that they call a halt at 2 MW in order to save money on accelerating components."

NLG is currently applying the finishing touches to a longer report that will also examine neutron provision after 2030. Among the options put forward to secure neutron supplies in the long term, says Carlile, are the formation of an umbrella organization to coordinate neutron-based research across Europe—akin to astronomers’ European Southern Observatory—and the construction of several other medium-flux neutron sources, each of which might cost about €500 million.