Washington

Nuclear physicists in the United States are rallying behind a plan to build two major new facilities in the next 10 years.

The two proposed facilities, for research on rare isotopes and on neutrinos, respectively, are backed in a strategic plan just endorsed by the US government's Nuclear Science Advisory Committee (NSAC). But the committee says that the facilities should not go ahead unless extra money is made available for their construction — and this is cash that even committee members acknowledge will be hard to come by.

Gamma-ray detectors, such as this one at the Berkeley lab, can aid in the study of rare isotopes. Credit: LBNL

The Rare Isotope Accelerator (RIA), the panel's top-priority new facility, would allow nuclear physicists to observe 'exotic' isotopes. The RIA would be more flexible than existing isotope accelerators, its advocates say. Heavy ions would be accelerated into fixed targets at high energies, where their impact would produce a range of rare, short-lived isotopes that could be separated and studied. Researchers think that a better knowledge of such isotopes will further the understanding of how heavy elements form inside supernovae.

The second facility backed by the panel, the National Underground Science Laboratory (NUSL), would study the almost-undetectable particles called neutrinos. The laboratory would be buried some 7 kilometres below ground, to shield its detectors from cosmic rays and other unwanted signals. Currently, US researchers interested in neutrinos must work at underground detector facilities in Japan, Canada or Europe. Neutrino research is part of the US nuclear physics programme for historical reasons.

But members of NSAC concede that it will be tough finding money for the two facilities. With its cost estimated at $700 million, the RIA would put enormous pressure on the physics budgets of the Department of Energy and the National Science Foundation (NSF). Even so, says James Symons, chair of the committee and a nuclear physicist at Lawrence Berkeley National Laboratory in California, the country should start thinking about the project now. In the end, Symons thinks, any decision to build the RIA will depend on how the proposal stacks up against desired big projects in other sub-disciplines, such as the Next Linear Collider being sought by high-energy physicists.

The NUSL proposal is associated with a site at the Homestake mine in South Dakota (see Nature 415, 105; 2002), and has become an issue in a hotly contested campaign for November's election of a South Dakota senator. But the NSF has responded cautiously to suggestions that it should help to build the NUSL, as this would strain its limited budget for large facilities. “There are great political machinations involved,” says NSAC member Alice Mignerey, a nuclear physicist at the University of Maryland. “But we were very careful that it was the science that drove the recommendation.”

Top of the priority list in the 10-year plan, however, is full-capacity operation of the two largest existing nuclear-physics facilities — the Relativistic Heavy Ion Collider at Brookhaven National Laboratory in New York state, and the Continuous Electron Beam Accelerator Facility at the Jefferson Laboratory in Virginia. A proposed 6% increase in next year's nuclear-physics budget at the Department of Energy would allow that goal to be met immediately, if it is approved by Congress (see Nature 416, 251; 2002). Symons believes that nuclear physicists would then be poised to make some exciting discoveries. “I think this is going to be a great decade for our field,” he says.