Frequently Asked Questions
Cosmic radiation—mostly protons traveling at very high speed—constantly bombards the earth, creating a shower of secondary particles, including muons. Deep underground laboratories shield sensitive physics experiments from this cosmic noise. Italy, Japan, Canada and China currently have the largest, deepest underground labs, where scientists are looking for answers to fundamental questions, such as why matter exists and how the universe evolved. Their research includes experiments to explore the properties of subatomic particles called neutrinos and detectors searching for a mysterious substance called “dark matter”—the dominant form of matter in the universe but which, so far, remains undetected.
The Homestake gold mine in Lead, South Dakota, is a physics landmark. In 1965, nuclear chemist Ray Davis installed an experiment 4,850 feet underground in the mine. His goal was to detect neutrinos produced by the sun, and his discoveries earned him a share of the 2002 Nobel Prize for Physics. In September 2000, when Homestake announced it would close the mine, physicists proposed converting it into a deep underground laboratory. Homestake’s advantages were obvious. The mine is 8,000 feet deep, with 370 miles of tunnels, 14 shafts and numerous excavated caverns. The underground infrastructure is big enough and deep enough for a range of physics experiments, and geologists and biologists soon joined the national collaboration of scientists proposing the underground facility.
The first two major physics experiments on the 4,850-foot level will be installed during 2012, in an area called the Davis Campus in honor of the late Ray Davis.The Large Underground Xenon (LUX) experiment aims to become the world’s most sensitive detector to look for a mysterious substance called dark matter. Thought to comprise 80 percent of all the matter in the universe, dark matter remains undetected so far. LUX will be installed in the same cavern Ray Davis used, now enlarged and specially equipped for its new role.The Majorana Demonstrator experiment will be installed nearby in a large new hall called the Transition Area. Majorana will search for an extremely rare form of radioactive decay—neutrinoless double-beta decay. This experiment will help determine whether neutrinos are their own anti-particles, a discovery that could help physicists better understand how the universe evolved.
A number of scientific collaborations are considering the Sanford Lab for future experiments. The Department of Energy, for example, has begun the formal process of evaluating the proposed Long-Baseline Neutrino Experiment (LBNE), which would partner Sanford Lab and Fermi National Accelerator Laboratory (Fermilab) in Batavia, Ill. Researchers would shoot a beam of neutrinos from Fermilab, through the earth, to an detector 800 miles away at the Sanford Lab.
The Sanford Lab also could host future generations of dark matter and neutrinoless double-beta decay experiments, as well as others. And plans are under way for a Sanford Center for Science Education on the surface campus. Philanthropist T. Denny Sanford designated that $20 million of his $70 million donation to the project be set aside to create an education center that will inspire students to consider careers in science and engineering. Pilot education programs at the Sanford Lab already have reached thousands of K-12 students in South Dakota. The Sanford Center for Science Education will provide education and research opportunities for decades to come.
Homestake Mining Co. sealed the mine shut in 2003, and it slowly began filling with water. Lab advocates, however, continued working on the project. In 2004, the South Dakota Legislature created the South Dakota Science and Technology Authority (SDSTA) to work with the scientists proposing the lab. In 2006, Homestake Mining Co. donated the underground mine to the SDSTA.In 2007, the National Science Foundation (NSF) selected Homestake as the preferred site for a proposed Deep Underground Science and Engineering Laboratory, or DUSEL. The NSF also funded a team of scientists and engineers to design a large, multi-level national underground laboratory at Homestake. U.C. Berkeley physicist Kevin Lesko led this scientific collaboration.Homestake’s selection also paved the way for the SDSTA to begin reopening the mine and pumping water out—funded by a $10 million HUD grant, $40 million from the state Legislature and a $70 million contribution from philanthropist T. Denny Sanford. The SDSTA’s plan was to reopen Homestake to the 4,850-foot level as theSanford Underground Laboratory. In December 2010, the project hit an unexpected snag. The NSF decided not to fund DUSEL beyond the preliminary design phase. However, the Department of Energy also was considering major physics experiments at Homestake. In July 2011, the DOE agreed to fund operations at the Sanford Underground Laboratory during fiscal year 2012, while weighing how to use Homestake’s great depth for larger, long-term experiments.With the NSF-led DUSEL proposal stalled but with the Sanford Lab ready for science at the 4,850-foot level, the project, headed by Dr. Lesko, has become the Sanford Underground Research Facility, or SURF at Homestake.