May 24, 2019
Since 2012, the Davis Campus at Sanford Lab has been making international headlines in the global particle physics community.
Tom Shutt and Richard Gaitskell of the LUX collaboration talk to dignitaries during the dedication of the Davis Campus in 2012.
Photo by Steve Babbit
In the last seven years, a laboratory nearly a mile below the unassuming city of Lead, S.D. has been making international headlines in the global particle physics community:
Inside the LZ water tank, assembly has begun on the Outer Cryostat Vessel. Photo by Matthew Kapust
For those who were present for the official dedication of the Davis Campus on May 30, 2012, such headlines may have seemed too ambitious—if not altogether out-of-reach.
Yet, since 2012, these headlines have bled into print, proving that the 30,000 sq. ft. facility on the 4850 Level of Sanford Underground Research Facility (Sanford Lab) is capable of housing incredibly-sensitive particle physics experiments.
The first two rare-event searches to move into the Davis Campus were the MAJORANA DEMONSTRATOR (MAJORANA) and the Large Underground Xenon Experiment (LUX).
Bill Harlan, the communications director for Sanford Lab in 2012, described the goals each experiment had at the time of the Davis Campus dedication: “MAJORANA’s goal is to prove that background noise at the Davis Campus is indeed ‘quiet’ enough to be worth the expense of searching here for neutrinoless double-beta decay, a process with an estimated half-life longer than a trillion times the age of the universe (if it happens at all). LUX too, a search for weakly interacting massive particles (WIMPs), is not only the most sensitive search yet, it’s a precursor to a bigger detector to be placed in the same spot, if it’s quiet enough.”
LUX was quiet. In 2013, after a three-month run, the detector was declared the world’s most sensitive dark matter detector.
In 2016, when LUX completed its search, professor of physics at Brown University and co-spokesperson for the LUX experiment Rick Gaiskell announced, “With this final result from the 2014-2016 search, the scientists of the LUX Collaboration have pushed the sensitivity of the instrument to a final performance level that is 4 times better than the original project goals.”
Meanwhile, MAJORANA was attempting a different search in laboratory just down the corridor. The goal of MAJORANA is to “demonstrate” that the collaboration’s technology—using ultra-pure crystals of a germanium isotope in a detector deep underground—could achieve background radiation levels low enough to justify building a larger detector. In 2018, the collaboration published a study in Physical Review Letters proving exactly that.
In the Davis Campus, both LUX and MAJORANA collaborations proved their ability to achieve backgrounds low-enough to observe incredibly rare events. These findings paved the way for next-generation experiments.
The Davis Campus will be home to one of those forward-reaching experiments, the LUX-ZEPLIN (LZ) dark matter detector. LZ is currently being assembled in the same water tank that once housed its predecessor LUX. Peering down into the LZ water tank from the work deck above, researchers and engineers can see the assembly process for the 10-ton experiment underway. The Science and Technology Facilities Council’s Pawel Majewski recently returned to Sanford Lab after nearly half a year away, and was thrilled with what he saw.
“I’m very excited. Activities are happening at full steam, which is great!” said Pawel, whose focus is LZ cryostat installation. “The underground area looks ready to welcome an experiment.”
MAJORANA will take an active role in preparation for the next-generation search for neutrinoless double-beta decay: LEGEND-200 (Large Enriched Germanium Experiment for Neutrinoless ββ Decay). Although LEGEND-200 will be housed in Italy at Gran Sasso National Laboratory, ultra-pure copper electroformed by the MAJORANA collaboration will be used for the experiment.
MAJORANA will also be used to validate the detectors created for LEGEND-200. “MAJORANA has proven itself fantastic for characterizing detectors,” said Christofferson. “When detectors are created for LEGEND-200, they will be placed in the MAJORANA experiment to be validated. This helps us figure out how they respond while next-generation experiment is still being built, which is time well-spent before they go into the final experiment.”
With LZ anticipating data collection in 2020 and LEGEND-200 expecting first measurements in 2021, the physics community can soon expect more headlines rising from the underground Davis Campus at Sanford Lab.
“The Davis Campus has become exactly what we hoped for—a lab where great science is happening every day a mile underground,” said Mike Headley, the executive director of Sanford Lab. “The science results from the Davis Campus experiments have been world-leading, and we look forward to even more progress into the future.”
Read more about the Davis Campus history, renovation and dedication.
See the full article here .
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The Sanford Underground Research Facility in Lead, South Dakota, advances our understanding of the universe by providing laboratory space deep underground, where sensitive physics experiments can be shielded from cosmic radiation. Researchers at the Sanford Lab explore some of the most challenging questions facing 21st century physics, such as the origin of matter, the nature of dark matter and the properties of neutrinos. The facility also hosts experiments in other disciplines—including geology, biology and engineering.
The Sanford Lab is located at the former Homestake gold mine, which was a physics landmark long before being converted into a dedicated science facility. Nuclear chemist Ray Davis earned a share of the Nobel Prize for Physics in 2002 for a solar neutrino experiment he installed 4,850 feet underground in the mine.
Homestake closed in 2003, but the company donated the property to South Dakota in 2006 for use as an underground laboratory. That same year, philanthropist T. Denny Sanford donated $70 million to the project. The South Dakota Legislature also created the South Dakota Science and Technology Authority to operate the lab. The state Legislature has committed more than $40 million in state funds to the project, and South Dakota also obtained a $10 million Community Development Block Grant to help rehabilitate the facility.
In 2007, after the National Science Foundation named Homestake as the preferred site for a proposed national Deep Underground Science and Engineering Laboratory (DUSEL), the South Dakota Science and Technology Authority (SDSTA) began reopening the former gold mine.
In December 2010, the National Science Board decided not to fund further design of DUSEL. However, in 2011 the Department of Energy, through the Lawrence Berkeley National Laboratory, agreed to support ongoing science operations at Sanford Lab, while investigating how to use the underground research facility for other longer-term experiments. The SDSTA, which owns Sanford Lab, continues to operate the facility under that agreement with Berkeley Lab.
The first two major physics experiments at the Sanford Lab are 4,850 feet underground in an area called the Davis Campus, named for the late Ray Davis. The Large Underground Xenon (LUX) experiment is housed in the same cavern excavated for Ray Davis’s experiment in the 1960s.
In October 2013, after an initial run of 80 days, LUX was determined to be the most sensitive detector yet to search for dark matter—a mysterious, yet-to-be-detected substance thought to be the most prevalent matter in the universe. The Majorana Demonstrator experiment, also on the 4850 Level, is searching for a rare phenomenon called “neutrinoless double-beta decay” that could reveal whether subatomic particles called neutrinos can be their own antiparticle. Detection of neutrinoless double-beta decay could help determine why matter prevailed over antimatter. The Majorana Demonstrator experiment is adjacent to the original Davis cavern.
LUX’s mission was to scour the universe for WIMPs, vetoing all other signatures. It would continue to do just that for another three years before it was decommissioned in 2016.
In the midst of the excitement over first results, the LUX collaboration was already casting its gaze forward. Planning for a next-generation dark matter experiment at Sanford Lab was already under way. Named LUX-ZEPLIN (LZ), the next-generation experiment would increase the sensitivity of LUX 100 times.
SLAC physicist Tom Shutt, a previous co-spokesperson for LUX, said one goal of the experiment was to figure out how to build an even larger detector.
“LZ will be a thousand times more sensitive than the LUX detector,” Shutt said. “It will just begin to see an irreducible background of neutrinos that may ultimately set the limit to our ability to measure dark matter.”
We celebrate five years of LUX, and look into the steps being taken toward the much larger and far more sensitive experiment.
Another major experiment, the Long Baseline Neutrino Experiment (LBNE)—a collaboration with Fermi National Accelerator Laboratory (Fermilab) and Sanford Lab, is in the preliminary design stages. The project got a major boost last year when Congress approved and the president signed an Omnibus Appropriations bill that will fund LBNE operations through FY 2014. Called the “next frontier of particle physics,” LBNE will follow neutrinos as they travel 800 miles through the earth, from FermiLab in Batavia, Ill., to Sanford Lab.
The MAJORANA DEMONSTRATOR will contain 40 kg of germanium; up to 30 kg will be enriched to 86% in 76Ge. The DEMONSTRATOR will be deployed deep underground in an ultra-low-background shielded environment in the Sanford Underground Research Facility (SURF) in Lead, SD. The goal of the DEMONSTRATOR is to determine whether a future 1-tonne experiment can achieve a background goal of one count per tonne-year in a 4-keV region of interest around the 76Ge 0νββ Q-value at 2039 keV. MAJORANA plans to collaborate with GERDA for a future tonne-scale 76Ge 0νββ search.
CASPAR is a low-energy particle accelerator that allows researchers to study processes that take place inside collapsing stars.
The scientists are using space in the Sanford Underground Research Facility (SURF) in Lead, South Dakota, to work on a project called the Compact Accelerator System for Performing Astrophysical Research (CASPAR). CASPAR uses a low-energy particle accelerator that will allow researchers to mimic nuclear fusion reactions in stars. If successful, their findings could help complete our picture of how the elements in our universe are built. “Nuclear astrophysics is about what goes on inside the star, not outside of it,” said Dan Robertson, a Notre Dame assistant research professor of astrophysics working on CASPAR. “It is not observational, but experimental. The idea is to reproduce the stellar environment, to reproduce the reactions within a star.”