Workers at the Homestake mine evaluate the quality of the rock for construction of the large caverns that are expected to house DUSEL's experiments. Credit: Steve Babbitt, Black Hills State University/SDSTA

Ambitious plans to build one of the world's deepest underground laboratories have suffered a setback. The US National Science Board has refused to continue to fund the design of the Deep Underground Science and Engineering Laboratory (DUSEL), which is expected to be built in the Homestake former goldmine near Lead, South Dakota, at an eventual cost of US$800 million–$900 million.

The decision to halt funding for the project has exposed differences at the US National Science Foundation (NSF) regarding how its programme-based mission to advance science should apply to the construction of major science infrastructure — a task more often associated with other funding agencies such as the US Department of Energy.

The mine is almost 2,500 metres deep, so it is shielded from bombardment by cosmic rays, energetic subatomic particles from across the Universe that can create background noise in particle detectors. That makes the mine the perfect location for a range of sensitive experiments searching for hard-to-detect particles such as neutrinos and dark matter.

No one has had any hesitation with the science. We had concerns with the relative roles of the NSF with its partners. Mark Abbott , Oregon State University, Corvallis

The National Science Board (NSB) — which must approve large outlays by the NSF — decided on 2 December to refuse 'bridge funding' of $29 million. NSF programme managers had requested the amount to allow continued development of a design proposal that would in turn be voted on in 2011. Stakeholders are still reeling. "We don't know if this is a glitch or a death knell. I think the users feel like we're in limbo right now," says Steven Elliott, a neutron scientist at Los Alamos National Laboratory in New Mexico and chairman of the Executive Committee of the DUSEL Research Association, which represents around 1,000 researchers who expect to do science at DUSEL. Inadequate funding Edward Seidel, assistant director for mathematical and physical sciences at the NSF, says that$29 million that was awarded to the University of California, Berkeley, in 2009 to design and prepare the way for DUSEL had proved inadequate. Problems arose with ensuring that the mine shafts would be safe for scientists to access, and with pumping groundwater from the aging mine. So this month, programme managers returned to the NSB for permission to award another $19 million now, with perhaps another$10 million to come in the spring of 2011; both were refused.

More than $300 million has already been committed to DUSEL by the NSF and its partners. The money includes$80 million from the NSF, more than $100 million from the US Department of Energy,$70 million from Denny Sanford, a South Dakota philanthropist, and \$50 million from the state of South Dakota, which owns the Homestake mine.

Apart from the money being used to prepare the mine, much of the funding is going towards designing the experiments that will be lowered into caverns near the surface, and 1,500 and 2,300 metres underground. The rate of cosmic rays reaching detection equipment at this depth is millions of times lower than at the surface; a boon to sensitive experiments intended to study extremely rare processes, such as the hypothesized decay of the proton or uncommon nuclear reactions that help to power the sun. DUSEL is also slated to include the Long Baseline Neutrino Experiment — in which neutrinos will be fired at detectors in DUSEL from 1,000 kilometres away at Fermilab in Batavia, Illinois, to find out why there is so much more matter than antimatter in our Universe — and LUX, the world's most sensitive search for dark matter.

Building the lab would allow the United States to compete effectively with other countries that have underground facilities. These include the Super-Kamiokande neutrino observatory near Hida, Japan; Gran Sasso National Laboratory near L'Aquila, Italy; and the Sudbury Neutrino Observatory in Canada, says Rick Gaitskell, a particle astrophysicist at Brown University in Providence, Rhode Island, who hopes to use DUSEL. "Here in the United States we are conspicuous in not having a deep underground science lab, in contrast to other countries with large science programmes," he says.

Managing the infrastructure

"No one has had any hesitation with the science. We had concerns with the relative roles of the NSF with its partners," explains Mark Abbott, dean of the College of Oceanic and Atmospheric Sciences at Oregon State University in Corvallis, and a member of the NSB. In particular, board members felt that the Department of Energy could be contributing more. Officials at the Department of Energy declined interviews, but issued a statement saying that they were disappointed by, but accept, the NSB's decision.

Ray Bowen, a mechanical engineer at Texas A&M University in College Station and chairman of the NSB, says that the 16-member panel was worried about the proposed 'stewardship model' for running the lab. In this system, the infrastructure for each experiment is taken care of by an allocated lead agency. That seems to board members to leave the mine infrastructure as a whole unaccounted for, says Bowen, which raises the prospect that the NSF would be stuck with ballooning costs that it could not afford. "We found the 'stewardship model' was inadequate," he says.

Kevin Lesko, a neutrino astrophysicist at the University of California, Berkeley, and the principal investigator of DUSEL, says that the task of deciding what should count as central infrastructure and what is particular to experiments is part of the ongoing design work. "We are working proactively to make sure things are not getting left in the cracks," he says. Following the NSB decision, says Lesko, the DUSEL project team is talking to all of its partners to see what options they have for keeping design activities going.

Seidel comments that the decision absolutely does not mean the NSF will not build or steward the facility. "It's clear that the current stewardship model will have to change," he says, "clearly we're in a new place now"

The Homestake mine is currently home to the Sanford Underground Laboratory, which hosts earlier, smaller scale versions of two experiments intended for DUSEL. The lab has enough funding to continue maintenance of the mine until next May, says its spokesman, Bill Harlan. A final NSF decision on whether to go ahead with DUSEL was expected in 2011, but may now be delayed.