ROCKVILLE, MARYLAND—Physics fans, hold your breath: An underground lab that's absolutely vital to the future of particle physics in the United States will cost the Department of Energy (DOE) between $1.2 billion and $2.2 billion, according to a study presented today to the federal High Energy Physics Advisory Panel (HEPAP). Those numbers are not entirely surprising, as they essentially combine the money DOE would have spent on an experiment in the lab with a proposal that the National Science Foundation (NSF) spend $875 million to build the lab. But they will put a mighty strain on DOE's $795 million a year particle-physics budget and could significantly slow down another key project at the United States's only lab solely dedicated to particle physics. The report also dashes the dreams of some physicists to place some exquisitely sensitive experiments in the mine's lowest level, 2500 meters down.
Until recently, scientists had been hoping that NSF would convert the Homestake mine in the Black Hills of South Dakota into a Deep Underground Science and Engineering Laboratory (DUSEL). That facility would have housed a suite of big particle physics experiments, as well as smaller-scale research in geology, microbiology, and engineering. However, in December, the National Science Board, which sets policy for NSF, declined to continue development of the $875 million laboratory, objecting to a proposal that NSF spend $480 million on laboratory infrastructure and share other costs with DOE, which would build the biggest experiment to go into DUSEL. That decision left the project's fate in the hands of DOE, the primary support of particle physics in the United States.
So DOE's Office of Science asked a committee led by Jay Marx of the California Institute of Technology in Pasadena to evaluate the costs and risks of different options for the three main experiments slated for Homestake. The first is a gigantic particle detector known as the Long Baseline Neutrino Experiment (LBNE) to snare particles called neutrinos fired from Fermi National Accelerator Laboratory (Fermilab), 1300 kilometers away in Batavia, Illinois. The second is a detector weighing several tons to spot particles of the mysterious dark matter whose gravity appears to bind the galaxies. The third is a detector weighing at least a ton that would search for a revolutionary form of radioactivity called neutrinoless double beta decay.
The team considered two technologies for building LBNE 1480 meters down in Homestake. It considered three options for the dark matter experiment—building it at that depth, at a depth of 2250 meters, or at the existing SNOLAB in Sudbury, Ontario. The committee considered the same three options for the location of a neutrino-less double beta decay experiment.
Using data from the DUSEL design and other sources, Marx's team estimated that LBNE alone would cost between $1.2 billion and $1.5 billion using the more-established of the two technologies. That estimate ignores the cost of inflation over the decade it would take to build the detector. The dark matter and neutrinoless double beta decay experiments could be built at 1480 meters for $300 million and $400 million, it estimated. Building those two experiments at SNOLab would save about $100 million, Marx told HEPAP, although he noted there were advantages to having all three experiments at the same facility.
Marx emphasized that the committee was not making recommendations. "We were just trying to evaluate what it would take to implement these experiments with regard to risk, costs, and schedule," he says. Nevertheless, it seems clear that the report puts the kibosh on certain options. For example, the committee found that it would cost $700 million and $900 million, respectively, to build the dark matter and neutrinoless double beta decay experiments 2250 meters down. "We don't consider it a cost-effective option," Marx told HEPAP. So plans for a very deep level, which were once a selling point, seem dead.
The cost of LBNE may require a delay in Fermilab's plans for another big project, a high-power proton accelerator called Project-X to replace the lab's current complex of accelerators. In principle, that $1.8 billion project could be ready to run in 2020, says Fermilab Director Pier Oddone. If it were, it could generate neutrinos to shoot at the completed LBNE detector, feed a variety of other experiments, and secure Fermilab a broader future. But given the prospect of flat budgets for years to come, Fermilab will likely have to put Project-X on hold. "We're making a very clear prioritization that we want to do LBNE with existing accelerator complex, and Project-X will have to take its lumps in terms of scheduling," he says.
Of course, DOE officials first must decide if they want to build any of these experiments. And that won't happen until after the National Academies' National Research Council weighs in, likely within a month, on the scientific arguments for the lab, says William Brinkman, head of DOE's Office of Science. "As soon as that report comes, we'll be working on the [fiscal year] 2013 budget to figure out what we can do and what we can't do," says Brinkman. "It all depends on what we can afford."
The stakes are high. Not building LBNE might mean the end of Fermilab and the U.S. domestic particle physics program.