Particle accelerators and colliders are crucial to fundamental scientific research and breakthrough science and have led to discoveries in particle and high-energy physics, materials science, medicine, and many other fields, as well as enabling progress in research areas such as fusion. Superconducting magnets are essential components of accelerators as they produce the magnetic fields that guide and steer particle beams around the accelerator. Two types of magnets are used in accelerators: dipole magnets, which steer particle bunches in a ring, and quadrupole magnets, which compress and focus these bunches to help control the beam.
The development of more dipole powerful magnets enables researchers to achieve higher particle energy levels, and stronger quadrupole magnets squeeze the particle beams more tightly, increasing the rate of collisions at the interaction points. This improves the precision in accelerator experiments, expanding research opportunities and paving the way for new applications. However, the complex design, specialized materials, and cryogenic cooling systems needed to construct them and maintain their superconducting state make high-field strength superconducting magnets particularly challenging and expensive to build and operate.
Researchers in the Accelerator Technology & Applied Physics (ATAP) Division at the Lawrence Berkeley National Laboratory (Berkeley Lab) are leading efforts to develop advanced accelerator magnets. For instance, they are working with colleagues from the Lab’s Engineering Division to fabricate and assemble powerful new quadrupole magnets using niobium-tin (Nb3Sn) technology. These magnets, part of the ongoing contribution of the U.S. Accelerator Upgrade Project to the Large Hadron Collider (LHC) Accelerator Upgrade Project, or HL-LHC-AUP, generate much higher fields than the niobium-titanium magnets currently used in the LHC to create more tightly focused particle beams. This enhancement to the LHC, the world’s most powerful particle accelerator, will increase the collision rate of the accelerator’s proton beams, extending its capabilities.
“This is the first time Nb3Sn-based magnets will be used in a particle accelerator,” says Paolo Ferracin, a senior scientist and deputy head of ATAP’s Superconducting Magnet Program (SMP). “They will be installed in the interaction region of the LHC, resulting in a ten-fold increase in the accelerator’s luminosity and significantly increasing the amount of data the experimenters can collect. This could enable them to observe rare or unexpected processes or discover new particles.”
Niobium-tin quadrupole magnet MQXFA in the superconducting magnet assembly facility at Berkeley Lab. (Credit: Berkeley Lab)
He adds that these magnets result from over twenty years of R&D in Nb3Sn technology and “represent a significant milestone in advanced superconducting magnet technology, potentially ushering in a new era in accelerator science and applications.”
In addition to his scientific contributions to the field over the past three decades, Ferracin is also helping to nurture and develop the next generation of particle accelerator scientists and engineers. For more than a decade, he has taught courses on the science and technology of superconducting magnets for particle accelerators at the U.S. Particle Accelerator School (USPAS), a national educational institution offering courses on beam physics and related accelerator technologies, and at the Joint Universities Accelerator School (JUAS), an international graduate school for scientists and engineers pursuing a Master’s degree or working on a doctoral thesis.
In recognition of his contributions to JUAS, the school invited him to write a chapter for a book celebrating its 30th anniversary. Released on November 15, 2024, Proceedings of the Joint Universities Accelerator School (JUAS)—Courses and exercises (CERN, November 2024) features material from more than 60 authors who have taught and trained more than 1,400 students over the past three decades. According to the publishers, the book offers graduate science students “a broad and up-to-date introduction to the field” of particle accelerator science and applications.
Paolo Ferracin, senior scientist and deputy head of ATAP’s Superconducting Magnet Program, teaches a course at the Joint Universities Accelerator School. Credit (European Scientific Institute)
Ferracin’s chapter, “Superconducting magnets,” summarizes the content of his course and introduces superconducting magnets—specifically dipole and quadrupole magnets—for particle accelerators, along with the materials used to create them.
He says, “It addresses the fundamental principles, physical parameters, and analytical and numerical tools necessary for designing superconducting magnets for particle accelerators. The content is structured chronologically, highlighting the life cycle of these magnets—from conceptual design and fabrication to assembly and testing—along with the various stages of development and the professional journey of a magnet designer.”
Ferracin began working on superconducting magnets during his Master’s program at CERN, where he studied the structural behavior and field quality of the LHC dipole magnets. He continued this research as part of his doctoral studies, which examined the mechanical and magnetic characteristics of the LHC main dipole magnet.
“It was during my doctoral research that I first attended courses at USPAS,” he says. These courses, he adds, provided “a better understanding of the science behind superconducting magnets and how they have contributed to ever more powerful and capable particle accelerators.”
After completing his Ph.D. in 2002, he joined the SMP in Berkeley Lab’s Accelerator & Fusion Research Division (now known as ATAP) as a postdoctoral fellow. He was promoted to research scientist in 2004 and became a staff scientist four years later. In 2011, he accepted a position in the Magnets, Superconductors, and Cryostats Group—Technology Department at CERN before returning to Berkeley Lab as a senior scientist in 2020.
Paolo Ferracin. (Credit: Thor Swift/Berkeley Lab)
He says a highlight of his nearly 30-year career was being part of the team at Berkeley Lab that designed and assembled a Nb3Sn dipole magnet capable of producing a 16-tesla magnetic field—a world record in 2004. “I was fortunate to be involved in the design and fabrication of the magnet, which was a significant moment for me and the scientific community.” This proof-of-concept magnet paved the way for the upgrade of the LHC.
The Berkeley Lab team is finalizing the remaining Nb3Sn superconducting magnets for the HL-LHC-AUP. This collaborative effort involves scientists, engineers, technicians, and operations staff from CERN and four U.S. national laboratories: Berkeley Lab, Brookhaven National Laboratory, the National High Magnetic Field Laboratory at Florida State University, and Fermilab.
Another key R&D focus is developing the next generation of magnets made with high-temperature superconductors such as rare-earth barium copper oxide and bismuth strontium calcium copper oxide.
“While these materials could allow us to achieve a major jump in field strength, possibly more than 20 tesla, nearly double that of the new magnets for the high-luminosity upgrade to the LHC, their shape and properties are forcing us to re-think the design of magnets; so there’s a lot of R&D to do before such magnets become a reality,” says Ferracin.
He adds that developing these advanced magnet technologies aligns with a key recommendation from the 2023 Particle Physics Project Prioritization Panel (P5) Report, which calls for R&D on next-generation accelerators. These magnets could enable future colliders that utilize proton and muon or electron and positron beams, allowing researchers to reach energies of 10 TeV parton center-of-mass or higher. Such a collider could reveal the mysteries of the Higgs boson, characterize weakly interacting massive particles—hypothetical particles that are among the proposed candidates for dark matter—and search for evidence of new particles.
The work presented here was supported by the Department of Energy, Office of Science, Office of High Energy Physics, through the U.S. Magnet Development Program and the High-Luminosity Large Hadron Collider Accelerator Upgrade Project.
To learn more …
New Magnets for Large Hadron Collider Upgrade Successfully Pass Halfway Mark
The Challenges and Triumphs of Building Niobium-Tin Magnets
Niobium-Tin Superconductors: Fabrication and Applications
Cabling for LHC Upgrade Wraps Up
Building More Powerful Magnets From The Cables Up
For more information on ATAP News articles, contact caw@lbl.gov.
