Deep campus, low background

Just over a year ago, the Ross Campus looked very much like it had during mining days. Today, the world-class research space houses CASPAR (Compact Accelerator System for Performing Astrophysical Research) and the Black Hills State University Underground Campus (BHUC). While CASPAR is assembling its accelerator and expects to be operational in the summer, BHUC is open for business—the business of research. 

The BHUC has a class-1,000 cleanroom that houses ultra-sensitive low background counters that assay...

Learning from role models

Ginger Kerrick dreamed of being an astronaut. When she failed the medical examination, she found another way to stay in the space program—she became a member of the flight control crew as a Capsule Communicator, or Capcomm. The Capcom communicates directly with the astronauts while they are in space.

On Friday, Kerrick shared her story with more than 1,400 students at the American Physical Society (APS) Conference for Undergraduate Women in Physics. Kerrick, speaking from San Antonio, was connected to eight...

A stellar year for Sanford Lab

From SDSTA Executive Director Mike Headley

As 2015 comes to a conclusion, I’ve been reflecting on the incredible progress we’ve made this year at the Sanford Underground Research Facility (Sanford Lab). On many fronts plans are advancing to support our science activities today and to prepare for even larger experiments in the coming years. 

We are excited to be operating a new expanded science campus near the Ross Shaft on the 4850 Level and to be participating in the development of plans to...

Fire suppression system covers Ross Campus

The summer of 2015 saw the completion of the Black Hills State University Underground Campus (BHUC) and the CASPAR cavern (Compact Accelerator System for Performing Astrophysical Research) at the Ross Campus. The two projects added nearly 1,425 square feet to Sanford Lab’s underground footprint, increasing the need for industrial water underground.

It was a perfect time to upgrade the current water system that supplies water for drilling, cooling and fire suppression. The new upgrade required that a...

Heise to speak at Lead’s first ever Nobel Day

Starting at 4:01 a.m. on Oct. 6, SNO traffic was pretty heavy. SNO as in Sudbury Neutrino Observatory experiment. And Jaret Heise, Science Director at Sanford Lab, wasn’t surprised. Arthur McDonald, who lead the SNO experiment in Canada, had been awarded a share of the 2015 Nobel Prize in Physics for his discovery of neutrino oscillations.  

“We’d always hoped that SNO would win given the unique nature of the experiment,” Heise said. “I was pretty excited.”

As well he should be. Heise was a Ph.D....

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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