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...

Program gives students unique experience

Talk about a great summer gig. For 10 weeks, Dana Harvey learned all about modern research methods and tools through a National Science Foundation (NSF) program: Research Experience for Undergraduates (REU). 

“I got to see what it is like to really work in a lab,” said Harvey, a physics major at Davidson College in North Carolina. “It was a great experience. I learned a lot and got to do some cool research.” Harvey was one of six students who participated in this year’s program. The students each worked with...

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.

 

A ‘fitting tribute’ to visionary scientist

August 4, 2015
From Left: Mike Headley, Dale Lamphere, David Kieda, Roger Davis, Linda Davis, John Wilkerson and Joshua Willhite.

Bold visionary. Humble. Pioneer. Respectful. Passionate. Kind. Encouraging. Fun. Patient. Father. Husband. Scientist. Gentleman. Role model.

In a ceremony dedicating the Raymond Davis Jr. Memorial sculpture, speakers used all of these words to describe the man who built his solar neutrino experiment on the 4850 Level of Homestake Mine in the 1960s. Davis created “the solar neutrino problem” when his experiment detected only about a third of the neutrinos predicted. But he never gave up. In 2002, he received the Nobel Prize in Physics for his research.  

“Ray Davis had bold, visionary ideas,” said Dr. John Wilkerson, Principal Investigator with the Majorana Demonstrator Project and a former colleague of Davis. “He was a soft-spoken, polite gentleman who treated everyone around him with respect. This monument is a tribute to his vision and accomplishments.”

The sculpture, designed by South Dakota Artist Laureate Dale Lamphere, is a tank support from Davis’ experiment. The sculpture features a stainless steel ring that “floats” off the interior of the tank support. The original tank was moved in segments to the 4850 Level then assembled. The segmented monument reflects that process. 

“It was a great honor to create this tribute to Ray Davis and his profoundly important work,” Lamphere said. 

Dr. David Kieda was a graduate student when he arrived at Homestake in 1983 to work with Davis. Now the Dean of the Graduate School at the University of Utah, Kieda recalls the first time he saw the tank sitting in the cavern. “It was enormous!” he said. “I couldn’t understand how it got down that tiny shaft.” He learned soon enough.

“Seeing the monument today is like seeing an old friend. The tank allowed us to see into the sun, now it is in the sun. It is beautiful and simple and reflects the qualities of a man who treated everyone with the same kind of respect, regardless of who they were.” Kieda said.

The final speaker of the day was Roger Davis, son of Ray Davis. Roger Davis shared many stories about his father, “a dedicated scientist who always found time to play with his children.” 

Roger Davis and his four siblings, who grew up on Long Island, spent summers sailing, traveling and playing baseball. “My father was always the pitcher and he always pitched underhanded so everyone had the chance to hit a home run over the hedges out front.” And he treated every child in the neighborhood as if they were all his, including them in family outings and other activities, Roger said. 

Roger Davis summarized his father’s philosophy on life this way: “Exercise your body and your mind. Get a good education. Stay healthy. Listen to great music. Help others in need. Work hard and do your best. Be around children as often as you can. Never forget to have fun after your work is done. And never give up.”

The monument, he said, “is a fitting tribute to him.”

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