DUNE scientists observe first neutrinos with prototype detector at Fermilab

In a major step for the international Deep Underground Neutrino Experiment, scientists have detected the first neutrinos using a DUNE prototype particle detector at the U.S. Department of Energy’s Fermi National Accelerator Laboratory.

DUNE, currently under construction, will be the most comprehensive neutrino experiment in the world. It will bring scientists closer to solving some of the biggest physics mysteries in the universe, including searching for the origin of matter and learning more about supernovae and black hole formation.

Since DUNE will feature new designs and technology, scientists are testing prototype equipment and components in preparation for the final detector installation. In February, the DUNE team finished the installation of their latest prototype detector in the path of an existing neutrino beamline at Fermilab. On July 10, the team announced that they successfully recorded their first accelerator-produced neutrinos in the prototype detector, a step toward validating the design.

“This is a truly momentous milestone demonstrating the potential of this technology,” said Louise Suter, a Fermilab scientist who coordinated the module installation. “It is fantastic to see this validation of the hard work put into designing, building and installing the detector.”

The new neutrino detection system is part of the plan for DUNE’s near detector complex that will be built on the Fermilab site. Its prototype — known as the 2×2 prototype because it has four modules arranged in a square — records particle tracks with liquid argon time projection chambers. The final version of the DUNE near detector will feature 35 liquid argon modules, each larger than those in the prototype. The modules will help navigate the enormous flux of neutrinos expected at the near site.

The 2×2 prototype implements novel technologies that enable a new regime of detailed, cutting-edge neutrino imaging to handle the unique conditions in DUNE. It has a millimeter-sized pixel readout system, developed by a team at DOE’s Lawrence Berkeley National Laboratory, that allows for high-precision 3D imaging on a large scale. This, coupled with its modular design, sets the prototype apart from previous neutrino detectors like ICARUS and MicroBooNE.

Now, the 2×2 prototype provides the first accelerator-neutrino data to be analyzed by the DUNE collaboration.

DUNE is split between two locations hundreds of miles apart: a beam of neutrinos originating at Fermilab, close to Chicago, will pass through a particle detector located on the Fermilab site, then travel 800 miles through the ground to huge detectors at the Sanford Underground Research Facility in South Dakota.

The DUNE detector at Fermilab will analyze the neutrino beam close to its origin, where the beam is extremely intense. Collaborators expect this near detector to record about 50 interactions per pulse, which will come every second, amounting to hundreds of millions of neutrino detections over DUNE’s many expected years of operation. Scientists will also use DUNE to study neutrinos’ antimatter counterpart, antineutrinos.

This unprecedented flux of accelerator-made neutrinos and antineutrinos will enable DUNE’s ambitious science goals: Physicists will study the particles with DUNE’s near and far detectors to learn more about how they change type as they travel, a phenomenon known as neutrino oscillation. By looking for differences between neutrino oscillations and antineutrino oscillations, physicists will seek evidence for a broken symmetry known as CP violation to determine whether neutrinos might be responsible for the prevalence of matter — and hence everything — in our universe.

The DUNE collaboration is made up of more than 1,400 scientists and engineers from over 200 research institutions. Nearly 40 of these institutions work on the near detector. Specifically, hardware development of the 2×2 prototype was led by the University of Bern in Switzerland, DOE’s Fermilab, Berkeley Lab and SLAC National Accelerator Laboratory, with significant contributions from many universities.

“It is wonderful to see the success of the technology we developed to measure neutrinos in such a high-intensity beam,” said Michele Weber, a professor at the University of Bern — where the concept of the modular design was born and where the four modules were assembled and tested — who leads the effort behind the new particle detection system. “A successful demonstration of this technology’s ability to record multiple neutrino interactions simultaneously will pave the way for the construction of the DUNE liquid argon near detector.”

Next steps

Testing the 2×2 prototype is necessary to demonstrate that the innovative design and technology are effective on a large scale to meet the near detector’s requirements. A modular liquid-argon detector capable of detecting high rates of neutrinos and antineutrinos has never been built or tested before.

The existing Fermilab beamline is an ideal place for testing and presents an exciting opportunity for the researchers to measure these mysterious particles. It is currently running in “antineutrino mode,” so DUNE scientists will use the 2×2 prototype to study the interactions between antineutrinos and argon.

When antineutrinos hit argon atoms, as they will in the argon-filled near detector, they interact and produce other particles. The prototype will observe what kinds of particles are produced and how often. Studying these antineutrino interactions will prepare scientists to compare neutrino and antineutrino oscillations with DUNE.“Analyzing this data is a great opportunity for our early-career scientists to gain experience,” said Kevin Wood, the first run coordinator for the 2×2 prototype and a postdoctoral researcher at Berkeley Lab, where the prototype’s novel readout system was developed. “The neutrino interactions imaged by the 2×2 prototype will provide a highly anticipated dataset for our graduate students, postdocs and other young collaborators to analyze as we continue to prepare to bring DUNE online.”The DUNE collaboration plans to bombard the 2×2 prototype with antineutrinos from the Fermilab beam for several months.

Sergio Bertolucci, professor of physics at the University of Bologna in Italy and co-spokesperson of DUNE with Mary Bishai of Brookhaven National Laboratory, said, “This is an exciting milestone for the 2×2 team and the entire DUNE collaboration. Let this be the first of many neutrino interactions for DUNE!”

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.

Pantaleo Raimondi has long been fascinated by how things work.

“I like to understand everything. I don’t want to leave anything unexplored,” Raimondi said. “Even in a car, I try to understand exactly all the pieces that are there, why they work, and so on.”

It made some sense, then, that Raimondi opted to pursue a career in physics. “Physics really gives you a lot of answers,” he added.

But when he decided to come to Fermilab, America’s premier particle and accelerator physics laboratory, Raimondi said it was for the people.

“I have a good experience working in teams,” said the Italian accelerator physicist. “Since I have joined many, many teams in my life, I know how teams are, at a glance. And here at Fermilab, when I came, I realized that the team here is really beautiful.”

Raimondi is the new project director for the Proton Improvement Plan II. The PIP-II collaboration is upgrading the accelerator complex at the U.S. Department of Energy’s Fermi National Accelerator Laboratory, just outside of Chicago. To do this, a new superconducting linear accelerator is being constructed that will eventually send neutrinos to the Deep Underground Neutrino Experiment, enabling the advancement of neutrino physics for decades to come.

“Throughout my life, I’ve always been attracted by new experiments, new challenges, new projects,” he said. “I prefer to stay in one place, but then something else shows up and, somehow, I get attracted. This is true as well for PIP-II.”

“Leading PIP-II is a very challenging endeavor,” said Cristian Boffo, PIP-II project manager. “The technology that is being developed for the machine is beyond state of the art. Over 300 people from all Fermilab directorates work on PIP-II every day, and international partners from five countries provide significant in-kind components and share invaluable knowhow.”

“But in the few months since he joined Fermilab, Pantaleo has fully integrated into the team,” Boffo added. “He has begun providing precious guidance in key areas of the project and has set the pace for the years to come.”

The path to Fermilab

Raimondi did his graduate studies as part of the ALEPH particle detector collaboration at CERN in Switzerland. After earning his Ph.D., Raimondi went back and forth between a research center for the Italian National Agency for New Technologies, Energy and Sustainable Economic Development in Frascati, Italy, and SLAC National Accelerator Laboratory in Menlo Park, California.

Throughout this earlier part of his career, he worked on the design and development of radiofrequency power systems, theoretical and technical analyses of linear accelerators and microtrons, beam transport studies and other topics related to electron accelerators, beam-based alignment and final-focus systems.

Later, Raimondi was appointed head of the accelerator division at Italy’s National Institute for Nuclear Physics National Laboratory of Frascati in Rome. There, he participated in commissioning DAFNE, an electron-positron collider. Raimondi contributed to improving the understanding and performance of DAFNE and developed new techniques to improve its luminosity.

Most recently, Raimondi was based in Grenoble, France, at the European Synchrotron Radiation Facility. There, he led the upgrade of the ESRF synchrotron ring, building the brightest synchrotron source in the world — 100 times more powerful than its predecessor. His revolutionary design of the synchrotron’s “extremely brilliant source” is now being replicated by all major synchrotron light sources around the world, including Raimondi’s new neighbors at Argonne National Laboratory. Raimondi even spent time in Switzerland to discuss his lessons learned with CERN scientists to inform the development of their Future Circular Collider.

In January, Raimondi moved to the Chicago area and officially joined Fermilab. He was preceded by Rich Stanek, who had served as the interim director of PIP-II since April 2022.

Raimondi’s first taste of a Chicago winter didn’t faze him; he said that he likes the snow and the cold. In general, Raimondi enjoys spending time in nature and likes sports “of any kind.” So far, he said he’s done a lot of bicycling and running.

But some of his favorite activities cultivated in the French Alps, on the Italian coast and in California’s Bay Area are harder to do in Batavia — for example, paragliding, mountain climbing, surfing and wind surfing. “But,” he joked, “it’s good, because then I will focus more on working.”

Steering the boat

With his expertise in running projects in many different phases, Raimondi said he was comfortable jumping into a project that’s already moving along. “When I joined the project, it was in a very advanced state, and it’s doing very, very well,” he said.

In his first few months on the job, Raimondi said he’s trying to absorb a fire hose of new information. “I’m getting acquainted and trying to not do many stupid things,” he said.

“You can say that the project is like a big, huge boat. … At this stage, what is really important is removing the rocks, the obstacles from the path of the boat,” he said.

As one of Fermilab’s flagship projects, PIP-II has a never-ending stream of tasks for Raimondi to keep an eye on. The PIP-II site at Fermilab is under construction, new technology is being developed and components of the accelerator are being assembled and tested. For example, the team is assessing a prototype cryomodule after it was shipped to the United Kingdom and back to validate its transportation system; at the same time, they are preparing to assemble another unit in the newly qualified clean room at Fermilab.

“Pantaleo joined PIP-II at the right time,” said Allan Rowe, PIP-II technical integration manager. “As the project wraps up all final design activities, pushes through the procurement phase and begins detailed integration and commissioning planning, his experience from leading these efforts at ESRF and elsewhere will be invaluable.”

Raimondi thinks PIP-II is already “pretty solid.” As with any large project, there will be “ordinary challenges” related to executing the project on time and on budget. However, Raimondi assures that he and his team will get the new linear accelerator — and the physics results — done, no matter what.

As for the people, Raimondi is still impressed by the PIP-II team.

“Knowing more and more about my colleagues is a confirmation of my first impression,” he said. “I’m really looking forward to continuing.”

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.

 

Jennifer Ngadiuba has been fascinated by the universe since a young age. “I had binoculars to watch the stars,” said Ngadiuba, a Wilson Fellow at the Department of Energy’s Fermi National Accelerator Laboratory. But it was fundamental physics which grabbed her heart. “In high school the teacher gave us a book by Stephen Hawking, and I decided that’s what I wanted to do.”

Recently, Ngadiuba’s contributions to particle physics were recognized by the International Union of Pure and Applied Physics, who awarded Ngadiuba the 2024 Early Career Scientist Prize in Particle Physics.

“This award is one of the most prestigious worldwide,” said Anadi Canepa, the head of the Fermilab CMS group and the incoming deputy spokesperson of the CMS experiment. “It’s a testament to Jennifer’s vision, drive and her interdisciplinary approach to physics. She is a trail blazer and an outstanding physicist, and we are extremely proud of her achievement.”

Ngadiuba received the award on July 24, 2024, during a ceremony at the International Conference on High Energy Physics in Prague. In the announcement, IUPAP cited Ngadiuba’s contributions to ultra-fast machine learning techniques and their application to anomaly detection.

“Jennifer is using AI to reshape collider physics,” said Maurizio Pierini, the CMS physics coordinator. “I expect that in ten years from now, CMS and ATLAS will do things very differently from the way we do today and, looking back, we will track much of this evolution — which is actually an AI revolution — back to her work.”

During college, Ngadiuba developed a passion for experimental tools. “When I was studying physics, it was a lot of math, a lot of theory, and a lot of quantum mechanics,” she said. “I thought, I need to understand how we actually see all this. What is the instrument that allows us to make a theory not a theory?”

This curiosity led Ngadiuba to Fermilab, where as a master’s student she worked on tracking detectors R&D for the future upgrade of the Compact Muon Solenoid experiment, one of the two general purpose detectors at the Large Hadron Collider. But it was during a fellowship at CERN when she was captivated by machine learning.

“Things were changing in society,” she said. “There was this explosion of data in both science and industry.”

Machine learning has been used in physics analyses since the 1980s, but Ngadiuba was curious about its implementation in a new realm: the data collection itself. The LHC generates around 1 billion collisions a second, and physicists only have a few microseconds to decide which events are noteworthy and which can be discarded.

Ngadiuba wanted to integrate machine learning into this decision-making process but was at first hesitant. “I thought the LHC is too fast for machine learning,” she said. But this did not deter Ngadiuba and her colleagues. “The tools available from industry were not OK for us,” she said. “So let’s build our own.”

The result was a new tool called hls4ml, which allows physicists to program machine learning algorithms onto a type of chip called field-programmable gate arrays. Because FPGAs use parallel processing, they can analyze and reconstruct collision events much faster than traditional CPUs. The next step was finding a project in which they could deploy it.

“What’s the most interesting problem we want to tackle?” Ngadiuba said.  “That’s why we decided to do anomaly detection.”

Most physics searches start with a theoretical model and then look for evidence to support that theory. In anomaly detection, physicists start by looking for odd things in the data.

“It’s a paradigm shift,” Ngadiuba said.

This past spring, Ngadiuba and her colleagues installed their anomaly detection tool in the CMS trigger system and have already collected their first data set.

“Many people write very interesting papers on what ATLAS and CMS could do with AI,” said Pierini, who has been working with Ngadiuba since she was a PhD student. “Jennifer doesn’t stop there. She pushes her idea forward, to real-life applications that change things for real, not just in principle.”

In addition to her work on CMS, Ngadiuba is currently partnering with physicists on the Deep Underground Neutrino Experiment to integrate the techniques developed by CMS into neutrino research.

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.

Construction workers have finished the excavation of the huge caverns that will house the international Deep Underground Neutrino Experiment. While engineers and technicians are preparing for the installation of the gigantic neutrino detectors into these caverns a mile underground, scientists around the world are working to optimize DUNE’s particle detector technology.

From new photon detection systems to improved detector designs, researchers are refining devices and technologies to make DUNE’s neutrino detectors — liquid-argon time projection chambers — the best they can be for the most precise neutrino measurements.

The purity of the liquid argon inside the DUNE cryostats, which is crucial to observing particles and light created by neutrino interactions in the liquid, might get an upgrade too. An interdisciplinary team of researchers in Brazil discovered that a filter media typically used in industrial applications can filter out nitrogen contamination in liquid argon. Future large-scale tests will help determine whether this promising method might be applicable for DUNE.

“We started with the goal of finding new materials that could capture oxygen and water in a more efficient way,” said lead researcher Pascoal Pagliuso, a physics professor at “Gleb Wataghin” Institute of Physics, Unicamp in Campinas-São Paulo. “We decided to try and find a way to capture nitrogen, too. And we succeeded.”

Neutrinos are the most abundant matter particles in the universe, yet they are hard to detect. For DUNE scientists to observe some of the neutrinos flying through their gigantic particle detectors, the neutrinos must interact with something. In the case of DUNE, hosted by the U.S. Department of Energy’s Fermi National Accelerator Laboratory, neutrinos will collide with argon atoms. The process creates secondary particles that knock loose electrons and emit brief flashes of scintillation light. Instruments can record the electrons and light so that scientists can identify and reconstruct the particles and tracks that the collisions produce. However, for this measurement to happen, the particles need to have a clear, unobstructed path through the liquid argon all the way to the detection devices. In particular, the liquid argon has to be ultra-pure and contain few atoms of other elements that could absorb electrons or light.

A tricky challenge

Researchers and engineers ensure that the liquid argon in the detectors is as pure as it can be by filtering out contaminants like water and oxygen. These are two of the most common impurities. However, there’s a third contaminant that is common: nitrogen. While neutrino researchers have well-established methods to filter out water and oxygen, reducing nitrogen levels below the levels provided by commercial providers has been a challenge.

Nitrogen can have a significant impact on the results of experiments — up to 20% of scintillation light can be lost even with just one part per million of nitrogen present in liquid argon. With ambitious experiments such as DUNE, ensuring the quality of all detector components and materials to produce the best results is critical to finding out more about neutrinos and their role in the subatomic world.

Fermilab currently uses a molecular sieve and a copper material to filter out water and oxygen, respectively, but neither can capture nitrogen from liquid argon.

Led by Pagliuso, researchers in Brazil discovered a way to reduce even small contamination levels of nitrogen in liquid argon. His interdisciplinary team of physicists and engineers found a material that removes both nitrogen and water.

Combined with a filter media like the copper material used by Fermilab, the media can remove the three most common liquid-argon contaminants, ensuring the argon is as pure as possible for neutrino experiments.

The material is known as Lithium-FAU, a Faujasite LiX zeolite. This type of aluminosilicate material has industrial applications in refining petroleum and purifying air. The Brazilian team discovered it also has the ability to remove nitrogen from liquid argon through adsorption. “It’s like when you have a medicine for one disease and discover that it also works for another disease,” Pagliuso said.

When zeolites are used as adsorbents to refine or purify liquids and gases, they attract particular particles that will stick to their surface while allowing others to pass through the crystalline structure. It’s the concept also applied when putting packets of silica gel in new shoes to capture moisture: water clings to the surface of the silica gel beads so that the humidity won’t damage the shoes. In this case, the nitrogen molecules interact with the positively charged ions in the zeolite; the size of the lithium molecules is small enough to leave room for the nitrogen to be captured and for the liquid argon to flow free of contaminants.

The chemical engineering branch of the research team at Unicamp developed simulations to predict how nitrogen would be adsorbed by Li-FAU, giving DUNE experimenters the necessary framework for testing how the media performs in the specific environment of liquid argon in a cryostat.

“Predicting the behavior of the filter is important to determine the capacity of the filter,” said Dirceu Noriler, a professor and Director of the School of Chemical Engineering at Unicamp. “We helped the engineers design the filter by specifying the saturation time and number of cycles needed to reach the required purity.”

Successful tests

Researchers and engineers initially tested the media in the relatively small Liquid Argon Purification Cryostat at Unicamp with approximately 90 liters of liquid argon. Their successful results matched the simulations Noriler and his team had developed. Further testing took place this past fall at the 3000-liter ICEBERG test stand in Fermilab’s Noble Liquid Test Facility, which was filled with 2,625 liters of liquid argon for this particular test. The results confirmed Li-FAU’s ability to remove nitrogen from liquid argon at a larger scale.

“The Noble Liquid Test Facility here at Fermilab supports all sorts of liquid argon detector R&D, and we were very happy with the results. We intend to add Li-FAU to the facility as soon as possible so that, in addition to DUNE, all projects working on improving light collection systems can benefit,” said Flor de María Blaszczyk, R&D coordinator and test facility manager at Fermilab.

Not only will the purification media improve the quality of the liquid argon that Fermilab uses for experiments, but it would also allow for the removal of nitrogen contaminants if air would accidentally be introduced into the cryostat due to the malfunction of equipment. Nitrogen is the most abundant element in air, so knowing how to filter it out will be crucial for ensuring DUNE and other experiments won’t be compromised.

The next step is working to scale up the testing with larger volumes of liquid argon to ensure the media performs as well as it has so far. Scientists hope that ultimately the method will be capable of removing nitrogen at the large scale required for DUNE, which will feature detector modules that each contain 17,500 tons of liquid argon.

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.