Sir

As pointed out in your Opinion article “Anyone for neutrons?” (Nature 417, 883; 2002), the European Spallation Source (ESS) user meeting in May was an impressive demonstration of the lively activity of European neutron users. Five propositions for hosting the site of the ESS were presented, with backing from regional and/or national authorities.

It was surprising and regrettable to note the absence of a proposal for a French site. France has a long and deep tradition in the field of scientific use of neutron beams. It hosts the most powerful neutron source in the world, the Institut Laue Langevin (Grenoble), and a modern and well-equipped national source, the Laboratoire Léon Brillouin (Saclay). The French user community has declared its scientific interest in the ESS project on several occasions, and the French Neutron Users Society (http://www.sfn.asso.fr) has fully approved the goal of a new-generation neutron source in the next decade. A French team is heavily involved in the design and evaluation of the ESS.

Despite this commitment, no French site was proposed at Bonn, reflecting the obstacles raised by the diverging approaches of its national bodies (the Ministry of Research and Technology, and the two major funding agencies, the CEA and the CNRS). Moreover, the absence of high-level decision-makers representing French authorities at Bonn appeared as a sign of indifference.

It may be difficult in France at the moment to support large research infrastructures, and the financial climate may be unfavourable. But this does not excuse sacrificing the future. One cannot make progress by sticking to fixed schemes of funding and maintaining a conservative outlook on the merits of neutron science. The Bonn meeting showed the multidisciplinary and scientific potential of the ESS project. The present sources are needed to assure continuity, and to maintain and complete the training of the scientists who will run and use the source when it is completed.

As is usual in the case of any large-facility project, the construction phase of the ESS would require funding beyond the level of current functioning. But, considering the rapid expansion of the areas of science that will benefit from the new facility, the running costs will surely be reasonable.