Crews use old mining cars from the Homestake days in pre-excavation for LBNF/DUNE. Black Hills Pioneer file photo
This was not the first time the shafts, and drifts of the Homestake mine were used for advanced science. In 1965, Dr. Ray Davis installed a physics experiment 4,850 feet down inside the mine; cutting edge thinking by Davis at the time. Davis’ experiment set out to detect neutrinos coming from the sun. After nearly 30 years of detecting the tiny particles, his solar neutrino experiment had only uncovered around a third as many neutrinos as it should have; this lead to what was known as “the solar neutrino problem.” In working to solve Davis’ solar neutrino problem, scientists discovered that neutrinos can oscillate, or change their “flavor” as they travel through space. As a result, we now understand that there are three distinct types of neutrinos — electrons, muons, and taus. But why set up an experiment to detect particles from space nearly a mile underground? Neutrinos are part of a group of particulate matter known as WIMPs (Weekly Interacting Massive Particles), which means they are so infinitesimally tiny, that they can pass through solid matter. The dense rock that makes up the Black Hills works as a natural filter, stopping much of the background solar raFall, Winter • 2020–2021
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Destination Deadwood©
diation from making its way to the carved out caverns where the experiments are taking place. Scientists call this filtering process “cutting down the background noise,” and additional layers of filtration are used in the experiments to create the most “quiet” environment as possible to detect the elusive WIMPs. Much like gold panning in the old days, by eliminating all the particles they don’t want, scientists hope to spot the neutrinos they’re after. Davis’ experiment paved the way for what will be the Long Baseline Neutrino Facility (LBNF), which is currently in pre-excavation at the Sanford lab. LBNF will house the Deep Underground Neutrino Experiment (DUNE). LBNF/DUNE is a collaboration between the Sanford Lab in Lead, and Fermilab in Batavia, Ill. Once complete, LBNF/DUNE will be the largest neutrino study in the world. Using a particle accelerator, Fermilab will shoot a concentrated beam of neutrinos 800 miles through the earth to massive detectors deep underground at Sanford Lab in Lead. Four massive detectors will be installed 4,850 feet underground at Sanford Lab, consisting of huge cryostats (63 feet wide, 60 feet tall, and over 200 feet long) filled with a total of 70,000 tons of liquid argon and an array of detectors. The argon in the cryostats will “catch” neutrinos from the neutrino beam. Neutrinos interacting with particles of liquid
argon will produce other particles that will ionize the argon atoms and release electrons, which will be picked up by the detectors. Once that process has been studied, scientists at Fermilab will switch to an anti-neutrino beam. The results of the matter, anti-matter research could help scientists to better understand why matter won out over anti-matter at the point of the Big Bang. As you drive along Highway 14 through Lead, you will notice a large, 120-foot section of truss crossing over your head. This truss houses the conveyor system which will carry the more than 800,000 tons of rock excavated from the sight where LBNF/ DUNE will be built, to be deposited into the Open Cut. Excavation of the rock is scheduled to begin in early 2021, and the first detector should be ready to begin taking readings sometime around 2024 and 2025. The lab is home to numerous particle physics, geothermal, and dark matter detection experiments as well as the underground campus for Black Hills State University, which performs low background counts for SURF and other sensitive physics experiments from all over the world. To learn more about the Sanford Lab and Lead’s rich history of ground-breaking industry, visit the Sanford Lab Homestake Visitor Center located at 160, W. Main St.
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