Around a mile below the surface in South Dakota, construction crews are hard at work excavating around 1,000 tons of rock per day. Their goal is to make room for a large underground facility that will house an international effort aimed at studying neutrinos—highly elusive subatomic particles that may hold the key to many of the universe’s secrets.
The Long-Baseline Neutrino Facility will one day be home to the international Deep Underground Neutrino Experiment, hosted by the U.S. Department of Energy’s Fermi National Accelerator Laboratory. LBNF/DUNE involves more than 1,000 scientists and engineers from over 30 countries.
A construction miner stands near a bolter, a huge machine that installs 20-foot-long rock bolts in the caverns that will house the Deep Underground Neutrino Experiment. About 16,000 bolts will need to be installed to provide ground support in the gigantic, seven-story-tall caverns a mile underground. Photo: Jason Hogan, Thyssen Mining Inc.
DUNE has three main scientific aims: determine whether neutrinos might hold the key to the matter-antimatter asymmetry that gave rise to our matter-filled universe; look for neutrinos that indicate the birth of a neutron star or black hole, two of the most mysterious objects in space; and search for subatomic signals that could help scientists develop a theory that unifies the four forces of nature.
“DUNE is a unique experiment,” said DUNE co-spokesperson Sergio Bertolucci. “It is the only experiment where you can measure all the parameters of neutrino oscillations in the same place. This will enable us to perform precision measurements of the mass ordering, of the matter-antimatter symmetry violation and of the mixing angles.”
LBNF provides the space, infrastructure and particle beam for the experiment: the caverns that will house DUNE’s detectors—a near detector at the Fermilab site, and a far detector 800 miles away at the Sanford Underground Research Facility in South Dakota; the space for cryogenic equipment to keep these instruments cold; the hall where neutrinos are produced; and the beamline that will deliver the protons that make the neutrinos.
PIP-II, the Proton Improvement Plan II at Fermilab, will power the particle beam for the experiment. At the heart of PIP-II is the construction of a 700-foot-long particle accelerator that will boost a stream of protons to 84% of the speed of light. The construction of the first of two large buildings for PIP-II is almost complete. When operational, PIP-II will feed its protons into a chain of accelerators to create the world’s most intense neutrino beam.
Excavation is in full swing
On-site prep work for the excavation of the LBNF far site facility in South Dakota began in 2019. In 2021, construction crews started the excavation of the large caverns for DUNE. The three LBNF caverns will house the far detector modules and the infrastructure needed to operate the detectors. Project managers expect the construction of the caverns to be complete in 2024.
“It doesn’t matter how many times you see it—these caverns are gigantic. It’s very impressive to see.” – Josh Willhite
To date, approximately 274,000 tons of rock have been removed—more than a third of the whopping 800,000 tons that needs to be extracted from a mile underground. About 200 people in South Dakota directly work on LBNF during this phase of the project.
Once complete, the underground facility with its three caverns will cover the area of about the size of eight soccer fields. Two of the caverns are about 500 feet long, 65 feet wide and 90 feet high—about the height of a seven-story building. These caverns will house the far detector modules, each of which will be more than 200 feet in length and contain 17,000 tons of ultrapure argon cooled to minus 184 degrees Celsius. The third cavern, which is about 625 feet long and 65 feet wide but is only 36 feet tall, will contain the cryogenic support systems, detector electronics and data acquisition equipment.
Drill and blast
The excavation of each cavern proceeds from the top to the bottom. The process is carried out by contractor Thyssen Mining Inc. and uses the so-called drill-and-blast technique. First, construction workers drill a series of holes, then load those holes with explosives that will blast away the rock. The workers then remove the blasted rock and transport it to large buckets called skips, which travel up a mile-long shaft to bring the rock to the surface. Once the rock is above ground, it is crushed, put on a conveyor, and then deposited into a former open mining pit called the Open Cut.
Next, workers move into the excavated space to conduct ground support, which involves operating gigantic drills that insert 20-foot-long bolts into rock walls as anchors. Miners will install a total of about 16,000 rock bolts to secure all walls and ceilings of the excavated space.
“These secure the rock because sometimes, in the process of blasting, you create fractures in the surrounding rock, or there’s existing fractures,” said Syd De Vries, a mining engineer at Fermilab. “That creates zones of weakness, so you install these rock bolts, along with a wire mesh that secures the rock so that it’s safe to go in and repeat that cycle.”
Once the ground support is complete, the drill-and-blast cycle begins anew. Some of the underground work can be carried out in parallel, with approximately 30 miners per shift working at different locations.
The drill-and-blast phase will be complete in the fall of 2023. “That’s the last time we’ll use explosives,” said Josh Willhite, a mechanical engineer who grew up in South Dakota and started working on the early plans for this project in 2010.
To complete the construction of the caverns, the floors and walls will be covered with concrete—and that work is expected to continue until May 2024.
Advances at all levels
While the excavation work proceeds, another set of contractors is preparing for the building and site infrastructure phase. During this phase, the LBNF space will be outfitted with the infrastructure needed to run the DUNE detectors. This includes setting up the lighting, electrical equipment, ventilation and piping that will direct argon delivered at the surface to the detectors deep underground.
Work on the DUNE particle detectors is advancing as well. For example, scientists in the UK have begun the mass production of large detector components for the first detector module in South Dakota. At the European laboratory CERN, the DUNE collaboration is about to start tests for vertical-drift detector components, which will be used in the second detector module to be built in South Dakota. At Fermilab, scientists are getting ready to test near-detector components built in Switzerland.
Prep work is paying off
Before the drill-and-blast process could begin in South Dakota, the project team completed the pre-excavation phase, during which the LBNF far site was prepared for the excavation. It involved, among other things, renovating the Ross Shaft, updating the rock crushing system and building the 3/4-mile-long conveyor system that moves the rock from the shaft to the Open Cut. “That was a pretty major scope of work,” Willhite said. “Seeing all that functioning and working properly once we got into excavation was pretty exciting.”
Work in progress: About 800,000 tons of rock need to be removed to create the seven-story-tall caverns and the connecting drifts for the LBNF far site location in South Dakota. Photo: Adam Gomez, SURF
During that phase, engineers also drilled a series of core samples to determine the geological characteristics of the rock, such as its strength and the presence of fractures, as well as the stresses that were present. Stresses on the rock exist both in the vertical and horizontal planes. The deeper you go, the greater the weight of the rock becomes, creating stress in the vertical plane. Horizonal stresses are caused by things like the tectonic activity of the Earth.
This diligent pre-excavation work has paid off. Project managers think that any big issues would have come up during the first year of excavation, but so far, the miners have successfully excavated the tops of all three caverns and have opened one of the caverns to its full width without any major setbacks. “The sensors that have been installed and are monitoring the rock movement are all following the predicted paths,” said De Vries. “That gives everybody a higher sense of security.” The monitoring, of course, continues, and the safety of all workers remains the project’s top priority.
Breaking the 625-foot-long utility cavern to its full length, then being able to walk along it, was an amazing feat, Willhite said: “It doesn’t matter how many times you see it—these caverns are gigantic. It’s very impressive to see.”
Fermi National Accelerator Laboratory is supported by the Office of Science of the U.S. Department of Energy. The 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.
Physicists love to smash particles together and study the resulting chaos. Therein lies the discovery of new particles and strange physics, generated for tiny fractions of a second and recreating conditions often not seen in our universe for billions of years. But for the magic to happen, two beams of particles must first collide.
Researchers at the U.S. Department of Energy’s Fermi National Accelerator Laboratory have announced the first successful demonstration of a new technique that improves particle beams. Future particle accelerators could potentially use the method to create better, denser particle beams, increasing the number of collisions and giving researchers a better chance to explore rare physics phenomena that help us understand our universe. The team published its findings in a recent edition of Nature.
The beam particles each emit ultrafast light pulses as they pass through a special magnet called a pickup undulator (bottom right). Information about each particle’s energy or trajectory error is encoded in its light pulse. The light pulses are captured, focused and tuned by various light optics. The particles then interact with their own pulses inside an identical kicker undulator (center). The interaction can be used to cool the particles or even control them depending on the configuration of the system. Image: Jonathan Jarvis, Fermilab
Particle beams are made of billions of particles traveling together in groups called bunches. Condensing the particles in each beam so they are packed closely together makes it more likely that particles in colliding bunches will interact—the same way multiple people trying to get through a doorway at the same time are more likely to jostle one another than when walking through a wide-open room.
Packing particles together in a beam requires something similar to what happens when you put an inflated balloon in a freezer. Cooling the gas in the balloon reduces the random motion of the molecules and causes the balloon to shrink. “Cooling” a beam reduces the random motion of the particles and makes the beam narrower and denser.
Scientists at Fermilab used the lab’s newest storage ring, the Integrable Optics Test Accelerator, known as IOTA, to demonstrate and explore a new kind of beam cooling technology with the potential to dramatically speed up that cooling process.
“IOTA was built as a flexible machine for research and development in accelerator science and technology,” said Jonathan Jarvis, a scientist at Fermilab. “That flexibility lets us quickly reconfigure the storage ring to focus on different high-impact opportunities. That’s exactly what we’ve done with this new cooling technique.”
The new technique is called optical stochastic cooling. It was first proposed in the early 1990s, and while significant theoretical progress was made, an experimental demonstration of the technique remained elusive until now.
This kind of cooling system measures how particles in a beam move away from their ideal course and then uses a special configuration of magnets, lenses and other optics to give corrective nudges. It works because of a particular feature of charged particles like electrons and protons: As the particles move along a curved path, they radiate energy in the form of light pulses, giving information about the position and velocity of each particle in the bunch. The beam-cooling system can collect this information and use a device called a kicker magnet to bump them back in line.
Conventional stochastic cooling, which earned its inventor, Simon van der Meer, a share of the 1984 Nobel Prize, works by using light in the microwave range with wavelengths of several centimeters. In contrast, optical stochastic cooling uses visible and infrared light, which have wavelengths around a millionth of a meter. The shorter wavelength means scientists can sense the particles’ activity more precisely and make more accurate corrections.
To prepare a particle beam for experiments, accelerator operators send it on several passes through the cooling system. The improved resolution of optical stochastic cooling provides more exact kicks to smaller groups of particles, so fewer laps around the storage ring are needed. With the beam cooled more quickly, researchers can spend more time using those particles to produce experimental data.
“It’s exciting because this is the first cooling technique demonstrated in the optical regime, and this experiment let us study the most the essential physics of the cooling process.” – Jonathan Jarvis
The cooling also helps preserve beams by continually reigning in the particles as they bounce off one another. In principle, optical stochastic cooling could advance the state-of-the-art cooling rate by up to a factor of 10,000.
This first demonstration at IOTA used a medium-energy electron beam and a configuration called “passive cooling,” which doesn’t amplify the light pulses from the particles. The team successfully observed the effect and achieved about a tenfold increase in cooling rate compared to the natural “radiation damping” that the beam experiences in IOTA. They were also able to control whether the beam cools in one, two or all three dimensions. Finally, in addition to cooling beams with millions of particles, scientists also ran experiments studying the cooling of a single electron stored in the accelerator.
The optical stochastic cooling apparatus occupies the entire six-meter length of IOTA’s long experimental straight. Designed and built by the IOTA/FAST team and industry partners, the system was recently used to achieve the world’s first demonstration of OSC. Photo: Ryan Postel, Fermilab
“It’s exciting because this is the first cooling technique demonstrated in the optical regime, and this experiment let us study the most the essential physics of the cooling process,” Jarvis said. “We’ve already learned a lot, and now we can add another layer to the experiment that brings us significantly closer to real applications.”
With the initial experiment completed, the team is developing an improved system at IOTA that will be the key to advancing the technology. It will use an optical amplifier to strengthen the light from each particle by about a factor of 1,000 and apply machine learning to add flexibility to the system.
“Ultimately, we’ll explore a variety of ways to apply this new technique in particle colliders and beyond,” Jarvis said. “We think it’s very cool.”
For more information about IOTA and optical stochastic cooling, read this article.
This work was supported by the U.S. Department of Energy Office of Science, SC High Energy Physics and National Science Foundation.
Fermi National Accelerator Laboratory is supported by the Office of Science of the U.S. Department of Energy. The 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.
Roger Snyder will become the permanent Department of Energy site office manager at Fermilab. Photo: PNNL
Effective Aug. 14, Roger Snyder will become the permanent U.S. Department of Energy Fermi Site Office manager for the Office of Science. Snyder has been the acting Fermi National Accelerator Laboratory site office manager since February while he continued a decade of service as site office manager at DOE’s Pacific Northwest National Laboratory.
It is not Snyder’s first time leading the site office team at Fermilab; he was the Fermilab site office manager in 2020. In his new assignment, Snyder will manage the site offices at both Fermilab and on an acting basis at nearby Argonne Laboratory until that position is filled.
“The proximity to both labs is great, because I can spend time at both locations,” said Snyder. “I hope this will bring Argonne and Fermilab a little closer together as well.”
Each site office supports the lab’s mission through a variety of roles and ensures that all lab operations are performed safely, securely and responsibly. All direct work at Fermilab is reviewed and approved by the site office.
“I hope to provide a degree of consistency as Director Merminga and her new team lead the lab, and I look forward to seeing the efforts that we have started together through to completion,” Snyder said.
Snyder has more than three decades of experience with the Department of Energy, both at DOE headquarters and a dozen DOE sites. They include Princeton Plasma Physics Laboratory and Savannah River, Sandia, Los Alamos, Lawrence Livermore and Pacific Northwest national laboratories.
“I am proud of the revitalization and modernization of PNNL over the last decade to the point of having the best metrics regarding maintenance in the complex,” he said. “I hope to bring forward the best of those experiences here at Fermilab as we prepare for our new missions and address our older facilities creatively.”
Snyder holds master’s degrees in engineering from the University of Maryland and in project management from George Washington University, and a bachelor’s degree in engineering from the University of Illinois Urbana-Champaign. He has held Project Management Institute, Stanford and DOE project management certifications and volunteers as an accreditor domestically and internationally for college engineering programs.
Fermi National Accelerator Laboratory is supported by the Office of Science of the U.S. Department of Energy. The 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.