ERT stages multi-agency drill

Emergencies happen all the time—at home, at play and at work. And when they do, you need to be prepared. That’s why the Sanford Underground Research Facility and its Emergency Response Team regularly carry out evacuation drills. Last week, the team went a step farther by staging and participating in a multi-agency emergency drill. 

“You train to be prepared for any emergency and we’re prepared because we train,” said John Emick, ERT lead. 

The team started with a table top exercise, with all agencies...

Preserving a piece of history

For just over 125 years, Homestake Mine operated the deepest, richest gold mine in North America. From 1876 to 2001, more than 40 million ounces of gold and 9 million ounces of silver were removed from a vast expanse of underground tunnels that stretched from the surface to the 8,000-foot level. As operations expanded and the company introduced new technologies, it built new buildings, removed old buildings and retired outdated equipment.

Homestake was selected as the site for a deep underground research...

TDM: Ensuring safe access for science

Every day, crews of infrastructure technicians convey people and equipment up and down the Yates Shaft. And it is mostly in this context that scientists, lab personnel and visitors see them. What we don’t see is the work the crews do to ensure every person—and everything—gets where they need to be, safely. 

“During the day, we mostly cater to science,” said Pat Urbaniak, team lead. “The night shift is where we do most of the challenging work.” That challenging work includes top-down maintenance (TDM), which...

Underground robot competition

On the surface, 16 middle-school students eagerly awaited the start of the Robotics competition taking place on the 4850 Level of Sanford Lab. 

“Are you ready?” asked Brianna Mount, research assistant professor of physics at BHSU, The students could see and hear the robots through a live internet connection. With a chorus of “Yes!” from the middle schoolers, the race was on. 

The students work in groups of two and are assigned a mentor from BHSU. Using LEGO Mindstorm kits, the eight teams from Belle...

Majorana wins big with 'second string'

In football, a coach has to be pretty desperate to put in the second string. The Majorana Demonstrator does things a little differently. Its second string—or cryostat—likely is the best. 

“Our experiment design includes a prototype, followed by two cryostats,” said Adam Bradley, a postdoc with Lawrence Berkeley National Laboratory who works on the Majorana Demonstrator project. “With each cryostat, we’ve learned what not to do or what to do better or how to be more efficient.”

Last year, the Majorana...

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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