Building on core knowledge

Long before Sanford Lab became the home to huge physics experiments, it was the Homestake Mine. Over its 126-year history, Homestake delved deeper and deeper to extract precious minerals. Eventually, Homestake’s footprint extended 8,000 feet below the surface and included a maze of tunnels, ramps and shafts that, if laid end to end, would measure nearly 370 miles—about the distance from Lead to Sioux Falls. 

During that time, Homestake compiled a vast knowledge of the fabric, or character, of the rock. As...

Ventilation critical to DUNE success

Air flows down the Yates and Ross shafts and is pulled through specific areas underground by two air shafts: Number 5 Shaft and the Oro Hondo. With the Deep Underground Neutrino Experiment (DUNE) just on the horizon, the reliability of the Oro Hondo ventilation system, in particular, is critical. 

A direct drive, variable-frequency fan powered by a 3000 horsepower synchronous motor (it currently draws less than 400 hp), the Oro Hondo was built in 1986. Since then, it has undergone repairs and had parts...

Neutrinos: Spies of the sun

As a young man, Frank Strieder was fascinated with astrophysics, reading every book he could find and taking high-level courses in math and physics while in high school in Germany. One day in particular stands out. 

“My teacher said, ‘Ah, but neutrinos have never been measured from the sun.’ I said, ‘No, no, no. There’s an experiment by Ray Davis somewhere in the United States at an underground gold mine.’ And the teacher said, ‘No, that is not the case,’” said Strieder, a professor of physics at the South...

Deep Talks looks at life underground

For more than 100 years, Homestake miners went deep to find gold. Today, scientists from around the world are going deep underground at Sanford Lab in search of microscopic organisims that could change life on the surface. 

South Dakota School of Mines and Technology biology professors and students are looking for ways to use microbes to convert solid waste into biofuels and bacteria into antibiotics. 

The NASA Astrobiology Institute, Desert Research Institute and Jet Propulsion Lab are studying life...

LUX: The end of an era

Five years ago, the Large Underground Xenon (LUX) experiment began its long journey to the Davis Cavern on the 4850 Level of Sanford Lab. Results published in 2013 proved LUX to be the most sensitive dark matter experiment in the world. When LUX completed its 300-live-day run in May of this year, the world learned LUX was even more sensitive than previously determined. 

Earlier this month, the LUX collaboration began decommissioning the experiment. “It’s bittersweet, the end of an era, but it was time,” said...

Mentors, students learn from competition

March 1, 2017
Brianna Mount watches as a BHSU mentor aligns a robot on the obstacle course. Students from Spearfish and Belle Fourche middle schools, designed, built and programmed the robots using LEGO Mindstorm kits.

Middle school students from Spearfish and Belle Fourche spent weeks designing, building and programming robots using LEGO Mindstorm kits for a robotics competition. They developed, altered and tested the course the robots would travel. On the day of the competition, they waved enthusiastically as their mentors, all students from Black Hills State University, took the robots nearly a mile underground to the 4850 Level where the competition took place. 

“The kids do all the work,” said Sam Hintgen, a junior science education major at BHSU. “As their mentors, we give them advice and encourage them to try new things.”

This is the second year Dr. Brianna Mount, research assistant professor of physics at BHSU, has overseen the competition. “Mentorship is an important component of this program and it means a lot to the kids.”  

Because the middle school students are too young to go underground, they watched the competition through a live internet connection, giving instructions and advice as their mentors placed the robots on the track. “Angle it this way,” said one child to his mentor; “Move it to the left,” said another.  

In the end, only two of the nine robots made it all the way through the track. But the competition was friendly and will serve as a lesson for the next one. 

“The best part about the competition is the trial and error,” Hintgen said. “They use real science to build the robots and learn from their mistakes.”

And the mentors learn as well. 

“The kids are awesome to work with,” said Taylor Watkins, a sophomore in environmental physical science at BHSU. “They are very appreciative and excited to see us every week. That’s really cool.”


LUX, now with more sensitivity

December 1, 2015
Photomultiplier tubes can pick up the tiniest bursts of lights when a particle interacts with xenon atoms.

The Large Underground Xenon (LUX) dark matter experiment, located on Sanford Lab’s 4850 Level is already the most sensitive dark matter detector in the world. Now, researchers have improved the detector’s sensitivity level, dramatically increasing its ability to find WIMPs (weakly interacting massive particles). 

Using a new set of calibration techniques, the research re-examines data collected during LUX’s first three-month run in 2013, and helps rule out the possibility of dark matter detections at low-mass ranges where other experiments had previously reported potential detections. 

“It is vital that we continue to push the capabilities of our detector in the search for elusive dark matter particles,” said Rick Gaitskell, Professor of Physics at Brown University and co-spokesperson for the LUX experiment.

Dark matter is thought to be the dominant form of matter in the universe and WIMPs are among the leading candidates. However, they interact with other matter on very rare occasions and they have yet to be detected directly.

LUX consists of one third of a ton of liquid xenon surrounded with sensitive light detectors inside a titanium vessel. On the very rare occasions when a dark matter particle collides with a xenon atom inside the detector, the xenon atom will recoil and emit a tiny flash of light, which will be detected by light sensors. So far, LUX hasn’t detected a dark matter signal, but its exquisite sensitivity has allowed scientists to all but rule out vast mass ranges where dark matter particles might exist. 

The new calibration techniques include injecting neutrons, which act as stand-ins for dark matter particles, into the detector, then track them to learn details about the recoil. The nature of the interaction between neutrons and xenon atoms is thought to be very similar to the interaction between dark matter and xenon. “It’s just that dark matter particles interact very much more weakly—about a million-million-million-million times more weakly,” Gaitskell said. He describes it as a “giant game of pool with a neutron as the cue ball and the xenon atoms as the stripes and solids.” 

Additionally, LUX scientists injected radioactive gases into the detector to better understand its response to the deposition of small amounts of energy by struck atomic electrons. The LUX improvements allowed scientists to test additional particle models of dark matter that now can be excluded.

“And so the search continues,” said Dan McKinsey, a University of California Berkeley Physics Professor and co-spokesperson for LUX and an affiliate with Lawrence Berkeley National Laboratory. “The latest run began in late 2014 and is expected to continue until June 2016. We will be very excited to see if any dark matter particles have shown themselves in the new data.”

Planning for the next-generation dark matter experiment at Sanford Lab is already underway. In late 2016, LUX will be decommissioned to make way for the much larger xenon detector of the LUX-ZEPLIN (LZ) experiment, which will be filled with 10 tons of liquid xenon—three times the volume used for LUX.

“The global search for dark matter aims to answer one of the biggest questions about the makeup of our universe. We’re proud to support the LUX collaboration and congratulate them on achieving an even greater level of sensitivity,” said Mike Headley, Executive Director of the SDSTA.

The LUX collaboration is supported by the DOE and National Science Foundation (NSF). It includes 19 research universities and national laboratories in the United States, the United Kingdom and Portugal.

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