The view from Homestake. There are two main entrances to the mine, the Ross and Yates shafts. The Ross shaft, in the distance, is under refurbishment so scientists and construction workers use the Yates Shaft to access Sanford Lab.
The main entrance to Sanford Lab.
Going underground means dressing for mine work: protective coveralls, rubber boots, a carbon monoxide filter, and a hard hat with light are worn for the cage ride down. Guests to the mine get their gear in this room.
This carbon monoxide filter is worn in case of emergencies. While it doesn’t provide oxygen, it does filter harmful carbon monoxide from the air if there were to be a fire or other disaster.
Scientists and other frequent workers in the mine keep their gear in a separate area.
University of California, Berkeley graduate student Kelsey Oliver-Mallory works on the LUX dark matter experiment and was my guide for the first part of my visit.
Each person takes two identical metal tags. One goes on the “In” board (not pictured) and the other goes in his or her pocket. This system helps people above ground keep track of people below ground.
The mine elevators are known as cages.
Cages descend to the Davis Campus and ascend to the surface on a strict schedule. We took the 7:30 a.m. cage. While there’s an espresso machine underground, there is no cafeteria, so scientists who stay all day bring their own lunches.
Waiting for the cage ride. Backpacks and satchels are put in plastic bags to keep them from getting dirty and wet on the ride.
The cage starts to fill as people arrive. The maximum number of passengers on a normal day is 28 riders, but in an emergency, the cage can hold 36. This morning’s cage had fewer than a dozen passengers.
The journey down to the 4850 level (4,850 feet underground), where the Davis Campus is located, takes about 10 minutes. The Yates shaft is made of wood that is kept wet to prevent decay. As the cage descends, the pressure change can be felt in the ears and the air becomes warmer and more humid.
The cage operator communicates with an operator on the surface at the start and end of the ride. There are no lights in the cage or shaft other than headlamps.
The Black Hills region in western South Dakota is known for its rich stores of gold and silver. In fact, 41 million ounces of gold and 9 million ounces of silver were pulled from Homestake Mine in Lead, SD between the 1870s and early 2000s. During that time, 370 miles of mine tunnels were created, reaching depths of 8,000 feet. But in 2006 science took over: Sanford Underground Research Facility (Sanford Lab) is an underground particle physics research complex housed in the former mine, using the earth and rock to shield experiments from cosmic rays. The better the shielding, the more likely the scientists will detect neutrinos and suspected dark matter particles called WIMPs. Earlier this summer, Lead celebrated the ribbon-cutting of a new visitor center that highlights the history of the old mine and the current and future science at Sanford Lab.
The U.S. Department of Energy’s Lawrence Berkeley National Lab (Berkeley Lab) is a key player in the creation of Sanford Lab and in the operation of some of its current and future experiments, including the dark matter experiment called LUX and a neutrino experiment called the MAJORANA DEMONSTRATOR. Berkeley Lab is also managing the Berkeley Low Background Facility and the forthcoming LUX-ZEPLIN (LZ) dark matter project, which builds on the accomplishments of LUX.
As a science writer for Berkeley Lab, I was able to catch a ride on one of the mine’s elevators, called a cage, and descend 4,850 feet down to learn more about the science and the scientists who work on these projects.
The above slideshow illustrates what it’s like to go underground. The short video below shows the last few seconds of the cage ride and our exit into the space called the Davis Campus, completed in 2012 and home to the MAJORANA DEMONSTRATOR, the LUX experiment, and other facilities.
It takes about ten minutes to ride the cage down to the 4,850 level where LUX and the MAJORANA DEMONSTRATOR are located. This video captures the last few seconds of the cage ride and the entry into the Davis Campus.
In addition to checking out the MAJORANA DEMONSTRATOR and LUX projects, I joined a tour given to a group of esteemed scientists (including Berkeley Lab’s Eric Linder) who were in the nearby town of Deadwood, SD for a conference on particle physics and cosmology. As part of the tour, we traveled through unlit tunnels, visited construction sites of a future experiment, and walked through the refuge chamber, a shelter equipped with water, meal bars, and canisters of breathable air in case a fire or other disaster strikes.
I went underground at 7:30 a.m. and came back up at noon. My four and a half hours of being shielded from daylight and cosmic rays was pleasant enough, but when I stepped outside, above ground, I was glad to see a bright sun and feel the breeze on my skin.
Below is a slideshow that details the underground experiments. The short video that follows gives a sense of what it’s like to travel through the tunnels.
All photo and video credits: Kate Greene.
The Davis Campus, 4,850 feet underground, is home to the LUX dark matter experiment and the MAJORANA DEMONSTRATOR neutrino experiment. The campus is named after nuclear chemist Ray Davis who realized that all the rock surrounding the mine could block cosmic radiation and thus Homestake would be the perfect place to look for neutrinos emitted by the sun. In 1965, Davis’ Homestake experiment was the first to find solar neutrinos. He won the Nobel Prize for the discovery in 2002.
Charles Lichtenwalner, the lab coordinator underground, leads a science and operations debrief for everyone who just arrived.
The clean room to the MAJORANA DEMONSTRATOR. This experiment is looking for a rare form of radioactive decay called neutrinoless double-beta decay. If found it would confirm that neutrinos are their own antiparticles, helping to explain why there’s more matter than antimatter in the universe. A series of HEPA filters and dehumidifiers controls the environment so dirt and moisture from the shaft and tunnels don’t extend too far into the Davis Campus. Outside the clean room the particle count is relatively low at 5000 0.5 micron-sized particles per cubic foot. These scientists are preparing to enter the clean room that boasts a count of only 100 particles per cubic foot.
The wall in the LUX science office is covered in unicorns, the unofficial mascot of the experiment. LUX, which stands for Large Underground Xenon experiment, is looking for Weakly Interacting Massive Particles, or WIMPs. Scientists believe WIMPs could be responsible for dark matter, a mysterious presence that affects how large objects like galaxies form and move.
Outside the office is the upper level of the LUX experiment where scientists calibrate the response of the detector via the access area pictured here. At the heart of LUX is 370 kilograms of liquid xenon and 122 photomultiplier tubes, encased in a tank holding 71,600 gallons of pure, deionized water. It’s believed that WIMPs will knock into nuclei of xenon atoms in LUX just a few times a year, but if and when it happens, the photomultiplier tubes will be able to detect light created in the process.
Data from detectors and telemetry is transmitted via a cascade of cables.
Kelsey Oliver-Mallory, a UC Berkeley graduate student, and Steven Young, a SUNY Albany graduate student, stand outside the water tank that shields the the LUX detector inside. LUX is the most sensitive detector in the world for hunting WIMPs, but the next-generation detector, LUX-ZEPLIN (LZ) will go even further. LZ’s detector will use 10 tons of liquid xenon—45 times the amount in LUX—and will be 100 times more sensitive.
There are about a dozen paper-cutout unicorns that decorate the lab in surprising (and constantly changing) locations.
Putting my coveralls and boots back on, I joined a tour group of distinguished physicists who were in town for a particle physics conference.
This mine train took us through tunnels, called drifts, to other parts of the facility.
I sat at the back of the train and watched the light at the end of the drift recede. The tunnels were warm and humid, unlike the hallways and rooms in the Davis Campus. An extensive exhaust system consisting of huge fans on the surface pulls air up various exhaust shafts. Air doors create temperature and humidity dividers between different parts in the mine.
Along our journey, we came across Governor’s Corner, pictured. The area is named for Mike Rounds, former governor and current South Dakota senator. Governor’s Corner is a crossroads in the drifts between the Yates and Ross shafts.
Jaret Heise, science liaison director at Sanford Lab (blue hat), describes the future experiment that will be housed in this current area of construction: CASPAR, Compact Accelerator System for Performing Astrophysical Research. Scientists will use CASPAR to reproduce and study some of the nuclear reactions that occur within stars.
The door to the refuge chamber is shown here. The chamber is airtight to keep harmful gases from entering and to keep breathable air from leaving.
The refuge chamber is supplied with enough food, water, and tanks of air for 72 people for four days.
This video captures a few seconds of a train ride through unlit tunnels at the 4850 level.
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Lawrence Berkeley National Laboratory addresses the world’s most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab’s scientific expertise has been recognized with 13 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy’s Office of Science. For more, visit www.lbl.gov.
DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.
