Basic2Breakthrough: Making an impact with compact superconducting radiofrequency accelerators

What if Olympic officials could record sprinters’ times only to the nearest minute? “We would know who started the race, and who finished the race, but that’s it,” said Bryan Cardwell, a postdoctoral researcher at the University of Virginia. “There’s no way to know who arrived first and who arrived last.”

Cardwell and his colleagues on the CMS experiment are currently tackling a similar problem. The CMS experiment records the tracks and properties of subatomic particles created by the Large Hadron Collider, the world’s most powerful particle accelerator. As it stands, physicists get a picture of all the particles produced in a collision, but they have insufficiently detailed information about when the particles were produced or how fast they were traveling, making it difficult to tell them apart.

That’s why CMS scientists are building a new detector that will let them watch particle collisions as they unfold, with 30-picosecond (0.00000000003 second) accuracy.

“In 30 picoseconds, light moves about one centimeter.”

“In 30 picoseconds, light moves about one centimeter,” said Chris Neu, a professor at the University of Virginia. “We’re talking about measuring the time of arrival of very fast objects with a very high precision.”

Some scientists suspect that rare and massive particles that take a long time to decay could move more slowly than lighter, more common particles. This means that when they do finally decay, their “daughter particles” will be a step behind. The difference would be tiny; a photo finish after a race that is only four feet long. But scientists hope that a precise “stopwatch” detector will help them tell the difference.

“We’ll be able to see if any particles are habitually arriving late,” Cardwell said. “That is inherently interesting.”

Turning ripples into tsunamis

The new timing detector consists of two parts: a barrel equipped with roughly 10,000 crystal sensors, and end caps coated with hair-thin silicon wafers. While silicon sensors are common inside CMS, this new detector has a special gain layer that amplifies the signal before it is read out.

“A small signal is like a tiny ripple on the surface of the water, and it gets lost among the little waves around it, so it’s hard to tell exactly when it arrived,” said Artur Apresyan, a researcher at the U.S. Department of Energy’s Fermi National Accelerator Laboratory. “The gain layer turns the small signal into a fast-moving tsunami that stands out clearly from the background, making its arrival time very clear. This amplification feature is not present in other CMS detectors; it’s a new design specifically for timing detectors.”

Currently, scientists at Fermilab are building and testing the sensors and support structures in collaboration with their national and international partners.

“The work on the end cap timing detector at Fermilab has been a unique possibility for many junior researchers to participate in the design and construction of a novel kind of detector,” Apresyan said. “These kinds of opportunities are very rare in such large and advanced experiments, and Fermilab provides an exceptional opportunity to allow newcomers to join and learn cutting-edge detector technologies and their applications.”

Unveiling the dark sector

Once the finished detector is installed inside CMS, scientists hope that it will help them separate fast-moving particles from slow-moving dark matter, a mysterious class of particles that are only visible through their gravitational pull.

Dark matter is as good as discovered in the sense that we know it’s there.”

“Dark matter is as good as discovered in the sense that we know it’s there,” said Tevong You, a theorist at King’s College London. “The problem is that none of the Standard Model particles that we know of can account for the properties of dark matter.”

According to You, many theoretical models predict that — in addition to the stable dark matter particles — there could be an entire universe of dark sector particles that might have properties similar to the known particles of the Standard Model.

“Dark matter is very stable, but we also know that stable particles like protons are just a small subset of all visible particles,” You said. “Maybe dark matter is just one small part of an extended dark sector that is full of long-lived particles that can decay into visible matter.”

According to Cardwell, the LHC could be producing dark matter. These dark matter particles would eat up a lot of kinetic energy from the proton-proton collisions and turn it into mass via Einstein’s equation, E = mc². “This means they have less energy to go fast,” Cardwell said.

When these dark matter particles decay into visible matter, the resulting daughter particles would be lagging behind everything else produced during the collision. This is where the timing detector comes into play.

“If we can measure the time those particles are arriving, we can figure out if they came from a particle that moved a little slower before decaying,” Cardwell said.

Pinpointing exceptional events

The new timing detector will also give scientists a much clearer view of what exactly is happening when bunches of protons collide inside the LHC.

“Right now in CMS, we send something like 100 billion protons through 100 billion protons 40 million times a second,” Cardwell said.

Every time two bunches of protons cross, about 70 collide. Currently, scientists use the spatial coordinates of the smaller particles produced by the collisions to connect the dots and figure out which particles came from what collisions. But spatial orientation alone won’t be enough when scientists turn on the High-Luminosity LHC, which will increase the collision rate by up to a factor of five.

“When there are so many collisions, many of them will literally be at the same point in space,” Cardwell said. “But the collisions don’t all happen at the same time; they’re actually spread out over around 200 picoseconds. With a really, really precise timing detector, 200 picoseconds can suddenly become a very long time; I can slice that 200 picoseconds into a bunch of individual frames.”

These frames will allow scientists to disentangle the messy LHC collisions and pinpoint rare and exceptional events.

“The cool thing about this detector is that it will make everything CMS does better,” Cardwell said. “If we are searching for dark matter, if we are measuring the properties of the Higgs boson, if we’re doing anything at all, the quality of every measurement will increase.”

As a theorist, You is excited about this new timing detector because it will open new avenues for research.

“The best bet for a spectacular discovery at the LHC is through developing new types of searches and new ways of sifting through the data,” You said.

The United States is entering a new era of scientific discovery defined by world-class computing power, rapid advances in artificial intelligence and seamless integration of scientific data. At the center of this transformation is the Genesis Mission, a national effort to double the productivity and overall impact of American science within the next decade by leveraging the combined strengths of the U.S. Department of Energy’s 17 national laboratories. Fermi National Accelerator Laboratory is poised to play a critical role.

With expertise in high-energy physics, advanced computing, accelerator and quantum technologies, and microelectronics design, Fermilab is well-equipped to be a central contributor to the Genesis Mission’s goals. Deploying AI to make particle accelerators adaptive and autonomous will propel innovations in medicine, materials and energy. Simultaneously, advancing next-generation microelectronics will serve to secure U.S. technological leadership, economic prosperity and national security.

“The Genesis Mission represents a once-in-a-generation opportunity to transform how America does science,” Fermilab Director Norbert Holtkamp said. “By combining AI, advanced computing and the capabilities of the national laboratories, we can accelerate discovery while strengthening the scientific infrastructure that underpins U.S. leadership in particle physics and beyond. Fermilab is proud to help drive this national effort.”

“The Genesis Mission represents a once-in-a-generation opportunity to transform how America does science.”

Through these initiatives and more, Fermilab will help tackle ambitious, world-shaping challenges — and it comes to this work prepared. The lab brings decades of experience navigating complex challenges through large-scale collaborations with national laboratory partners, academia and industry.

“We’re also excited for what AI can mean for our operations at Fermilab,” Holtkamp added. “I believe AI can dramatically enhance the quality and efficiency for work across the laboratory. Not only will Fermilab help drive DOE’s Genesis Mission, but I believe Fermilab can also serve as a strong example in how AI can benefit the operations of the full U.S. national lab complex.” 

Advancing accelerator science

Fermilab will contribute to a seven-lab collaboration known as the Multi-Office particle Accelerator Team, or MOAT. The initiative focuses on using AI to advance accelerator science by supporting more efficient operations and streamlined accelerator research and development. These efforts are expected to shorten commissioning timelines and reduce operating costs while extending the benefits of accelerator technology to a wider range of industry partners.

Speeding up chip design

One of Fermilab’s flagship contributions is AXESS, shorthand for Accelerating eXtreme Environment Specs-to-Silicon. This ambitious project aims to revolutionize custom microelectronics chip design for specialized scientific applications. Fermilab already has deep experience in creating chips that can function in extreme environments, such as cryogenic temperatures or intense radiation. By using AI to compress the design process from months to minutes, AXESS will significantly boost national competitiveness and speed up the pace of innovation.

Supporting American Science Cloud

The lab is also providing the Fermi Data Platform to support the emerging American Science Cloud. Fermilab is leveraging its extensive experience in handling the massive amounts of data created by particle collisions to provide large-scale data storage to the Genesis Mission. This infrastructure will enable researchers from across scientific disciplines to access the datasets needed to accelerate their own discoveries, effectively turning decades of physics data into a national resource.

Quickening theoretical calculations

Fermilab’s work in Lattice Quantum Chromodynamics, or Lattice QCD, will strengthen a multi-lab effort called FemtoMind. Lattice QCD is the framework physicists use to understand the strong force that binds subatomic quarks together to form protons. By applying agentic AI to quicken these complex calculations and uncover new patterns in computer simulations that probe physics at the proton scale, FemtoMind will deepen our understanding of the matter that makes up everything we see around us.

Creating AI-ready data representations

Fermilab will also contribute to the TREASURE initiative, which aims to make vast datasets more accessible for groundbreaking research. This program standardizes data from both current and retired particle colliders, including the Large Hadron Collider at CERN and the Tevatron at Fermilab, to create AI-ready representations of physics data for cross-experiment analysis. TREASURE will also convert research papers, datasets and code into user-friendly forms that can be trusted by scientists as they search for physics beyond the Standard Model.

Applying AI to astronomy

Fermilab’s contributions to the Genesis Mission will extend to astrophysics through the AI Universe effort. Researchers plan to apply advanced uncertainty-quantification methods to a state-of-the-art AI model trained on more than 200 million astronomical observations. This work provides astrophysicists with the tools necessary to make more precise predictions and identify meaningful patterns within large-scale astronomy datasets.

Connecting expertise

“AI is most powerful when it connects expertise across domains and institutions,” said Nhan Tran, head of AI coordination at Fermilab. “Through the Genesis Mission, we can integrate data, tools and expertise from all 17 national labs, creating a unified AI ecosystem that accelerates breakthroughs far beyond what any single lab could achieve.”

As the Genesis Mission mobilizes the full power of the Department of Energy’s national laboratories, Fermilab is uniquely positioned to make vital contributions toward solving the nation’s most pressing scientific challenges. From supercharging microelectronics design and enhancing particle accelerator R&D to transforming data analysis, the lab is helping drive the next wave of American innovation and discovery science.

Experimental particle physicist Dave Newbold has been elected to serve as the new co-spokesperson for the Deep Underground Neutrino Experiment. He is well-known in the scientific community for his contributions to high-energy physics research and scientific leadership. DUNE, the largest neutrino experiment in the world, is hosted by the U.S. Department of Energy’s Fermi National Accelerator Laboratory.

Newbold is currently executive director of national laboratories at the Science and Technology Facilities Council in the United Kingdom, and prior to that he served as STFC’s director of particle physics.

He has been involved with DUNE since 2015, working on the data acquisition system and the production of accelerator and detector components provided by the U.K. Newbold will co-lead the project in its next stages of development, which include the installation and commissioning of the DUNE far detectors at the Sandford Underground Research Facility, production of the near detectors and preparations for the first scientific data and publications.

“It’s a huge privilege to be elected to the leadership of DUNE,” Newbold said. “After more than a decade of work, the next two years will be crucial for the experiment, as we enter the final stages of detector construction and installation and look towards the excitement of our first scientific results. I look forward to working with scientists, institutes and agencies worldwide to ensure the continued success of the program.”

Newbold’s tenure as DUNE co-spokesperson begins in early April, and he will serve in that role for two years.

“I would like to extend my thanks to Sergio Bertolucci for his leadership as co-spokesperson over the last four years. During this time, the collaboration reached several important milestones, and Sergio played a key role in shaping DUNE to reach this point,” said Sowjanya Gollapinni, current DUNE co-spokesperson. “Dave is an excellent physicist, and he brings extensive scientific management and leadership experience. I welcome Dave into his new role and look forward to working with him as we enter into a critical construction phase for DUNE.”

“After more than a decade of work, the next two years will be crucial for the experiment, as we enter the final stages of detector construction and installation and look towards the excitement of our first scientific results.”

The DUNE collaboration consists of an international team of more than 1,500 scientists and engineers from more than 35 countries and CERN.

DUNE consists of two state-of-the-art particle detectors that will be housed in the Long-Baseline Neutrino Facility. A smaller detector will be located at Fermilab in Illinois, and a much larger one will be constructed a mile beneath the surface at the Sanford Underground Research Facility in South Dakota. The South Dakota detector will be the largest of its type ever built and will use 70,000 tons of liquid argon and advanced technology to record neutrino interactions with unprecedented precision.

The experiment will be powered by Fermilab’s Proton Improvement Plan II. Currently under construction at Fermilab, PIP-II will produce the world’s most intense high-energy neutrino beam on its journey from Illinois to the Deep Underground Neutrino Experiment in South Dakota.

In 2024, DUNE achieved a major milestone with the completion of excavation for the underground lab space in South Dakota. Since that time, crews have been hard at work outfitting the space with infrastructure to support the experiment, such as electricity, water and networking capabilities. Cryostat construction will begin this year as the project enters its third and final phase.

DUNE is expected to begin collecting data in 2029.

When he’s working at SNOLAB, Hogan Nguyen’s day starts at 4:30 a.m.

After preparing his lunch — usually a sandwich or leftovers — and driving to his workplace near Sudbury, Canada, the Fermilab senior scientist dons 15 pounds of safety gear. Like a city commuter catching his subway, Nguyen and 30 to 40 other workers must be ready to leave on schedule at 6:30 a.m. Unlike a subway, however, their mass transit is an elevator, known to miners as a cage, that takes them more than a mile below Earth’s surface in four minutes.

As a class-2000 clean room, SNOLAB can have no more than 2,000 particles per cubic foot of air, so the experiments are additionally protected from trace radioactivity originating in common materials such as dirt. These factors make SNOLAB ideal for studying rare phenomena like dark matter or neutrino oscillations. Its namesake experiment is the Nobel Prize-winning Sudbury Neutrino Observatory, or SNO, which has since been upgraded to SNO+.

Today, SNOLAB hosts a number of neutrino and astroparticle physics experiments, one of which is the Super Cryogenic Dark Matter Search, or SuperCDMS. Along with the LUX-ZEPLIN experiment and the Fermilab-hosted Axion Dark Matter eXperiment-Gen2, SuperCDMS SNOLAB is a second generation dark matter search experiment. It is jointly funded by the U.S. Department of Energy Office of Science, the U.S. National Science Foundation, the Canada Foundation for Innovation, and the Natural Sciences and Engineering Research Council of Canada, with SLAC National Accelerator Laboratory serving as the lead laboratory.

After a timeline adjustment due to the COVID-19 pandemic, SuperCDMS’s installation, with the exception of its shielding, was completed last year. The collaboration just successfully cooled the experiment to the temperature required for the superconducting detectors to become operational, a temperature colder than outer space. Science-quality data taking is on schedule to start in mid-2026.

For Hsu, who has been part of CDMS efforts since 2007 when she was a postdoc at Fermilab, and Nguyen, who joined SuperCDMS in 2024, it’s a thrilling time. After recent retirements, they are now the only Fermilab representatives working on its installation, though Fermilab has been involved since the 1990s.

The predecessor to SuperCDMS was the Fermilab-led CDMS at the Soudan Underground Laboratory. After some minor upgrades, it became SuperCDMS Soudan, and operations ended in 2015. Three years later, SuperCDMS SNOLAB — an even bigger upgrade to CDMS — was approved for construction.

Today, the SuperCDMS collaboration has over 100 members from 25 institutions in North America, Europe and Asia. Member institutions contribute different pieces of the experiment, from the shielding, detectors and cold hardware to the background studies, reconstruction software, simulations and more.

“It’s like assembling a very intricate jigsaw puzzle where you have each piece made by a different person,” said Hsu, “and you expect it all to fit together perfectly the first time you try to put it together.” But before assembling a jigsaw puzzle, the pieces need to be in one place.

When the cage arrives underground, Nguyen and his colleagues must “tag in” — hang up their personal tags in a designated area to indicate who is underground. At the end of the day, they’ll remove their tags to ensure everyone knows who came back out.

Down here, Nguyen and the others always travel in groups flanked by guides: one leading and one behind. It is hot and dark, and everyone wears a headlamp. Together, they walk about a kilometer to the cavern that contains SNOLAB. Now they can finally remove the safety gear, take a shower and get dressed for the clean room — donning clean lab coveralls, hair nets, hard hats, safety glasses and safety boots — and eat breakfast in the underground kitchen. At last, they can enter the clean room and begin their eight-hour day of work.

For Nguyen and the half-dozen SuperCDMS collaborators typically with him, that has meant assembling and installing the latest dark matter direct-detection experiment.

Dark matter is the name given to a mysterious substance that makes up 85% of matter in the universe. It doesn’t interact with any kind of light and only interacts with gravity, so astrophysicists only know dark matter exists because we can observe its influence on normal matter.

In theory, dark matter particles are permeating Earth constantly — we just have to figure out a way to detect them. Physicists have approached the dark matter search with a variety of methods and types of experiments. As a direct-detection experiment, SuperCDMS looks for signals caused by dark matter particles themselves.

SuperCDMS is sensitive to so-called “light dark matter” — dark matter particles about the mass of a mass of a proton. It uses 10-centimeter-diameter silicon and germanium crystals that are photolithographically patterned with sensors. Scientists believe dark matter particles will scatter off the nuclei in the crystals and produce a type of vibration called a phonon.

The first phase of the cryogenic system takes the brunt of the heat load, cooling SuperCDMS from room temperature to 50 kelvin, about minus 370 degrees Fahrenheit. The next stage lowers the temperature from 50 kelvin to 4 kelvin, which is minus 452 degrees Fahrenheit, and the final stage brings it down to the goal of 0.02 kelvin — less than minus 459.6 degrees Fahrenheit.

Fermilab led the design and fabrication of the cryogenic system, the warm electronics and associated infrastructure, and the calibration system, which was designed and built by Hsu. Fermilab also contributed the seismic platform on which the entire experiment stands. The platform is supported by springs that absorb the shock from a seismic event, somewhat like the suspension system of a car.

All these systems had to be brought down, piece by piece, into SNOLAB via the lone elevator. “Ideally what you would want to do is assemble your whole experiment on the surface and then just plop it down there,” said Hsu. “But the cage is very small, so we have to bring everything down piecemeal and put it together underground.”

With cooldown completed, the collaboration is beginning to add voltage to the detectors to start measuring background and noise signals. They are aiming to start collecting publication-quality data later this year.

If dark matter exists in the form that SuperCDMS thinks it does, “the expected interaction rate is extremely low, said Hsu. “This is what we call a rare event search. If we’re lucky enough to even see a signal, we don’t expect to see more than a few events per year for our entire experiment.”

And when they do make a detection, SuperCDMS will ideally confirm this with signals from other dark matter experiments, like LUX-ZEPLIN.

In the end, the physicists are all excited to see the experiment function as designed, take good data, and hopefully make a detection. Basically, “I want to see us discover dark matter,” said Nguyen.

It would be quite a reward for those 4:30 a.m. wake-ups and long workdays.