Fermilab achieves world-record field strength for accelerator magnet

To build the next generation of powerful proton accelerators, scientists need the strongest magnets possible to steer particles close to the speed of light around a ring. For a given ring size, the higher the beam’s energy, the stronger the accelerator’s magnets need to be to keep the beam on course.

Scientists at the Department of Energy’s Fermilab have announced that they achieved the highest magnetic field strength ever recorded for an accelerator steering magnet, setting a world record of 14.1 teslas, with the magnet cooled to 4.5 kelvins or minus 450 degrees Fahrenheit. The previous record of 13.8 teslas, achieved at the same temperature, was held for 11 years by Lawrence Berkeley National Laboratory.

That’s more than a thousand times stronger magnet than the refrigerator magnet that’s holding your grocery list to your refrigerator.

The achievement is a remarkable milestone for the particle physics community, which is studying designs for a future collider that could serve as a potential successor to the powerful 17-mile-around Large Hadron Collider operating at CERN laboratory since 2009. Such a machine would need to accelerate protons to energies several times higher than those at the LHC.

And that calls for steering magnets that are stronger than the LHC’s, about 15 teslas.

“We’ve been working on breaking the 14-tesla wall for several years, so getting to this point is an important step,” said Fermilab scientist Alexander Zlobin, who leads the project at Fermilab. “We got to 14.1 teslas with our 15-tesla demonstrator magnet in its first test. Now we’re working to draw one more tesla from it.”

The success of a future high-energy hadron collider depends crucially on viable high-field magnets, and the international high-energy physics community is encouraging research toward the 15-tesla niobium-tin magnet.

At the heart of the magnet’s design is an advanced superconducting material called niobium-tin.

Electrical current flowing through the material generates a magnetic field. Because the current encounters no resistance when the material is cooled to very low temperature, it loses no energy and generates no heat. All of the current contributes to the creation of the magnetic field. In other words, you get lots of magnetic bang for the electrical buck.

The strength of the magnetic field depends on the strength of the current that the material can handle. Unlike the niobium-titanium used in the current LHC magnets, niobium-tin can support the amount of current needed to make 15-tesla magnetic fields. But niobium-tin is brittle and susceptible to break when subject to the enormous forces at work inside an accelerator magnet.

So the Fermilab team developed a magnet design that would shore up the coil against every stress and strain it could encounter during operation. Several dozen round wires were twisted into cables in a certain way, enabling it to meet the requisite electrical and mechanical specifications. These cables were wound into coils and heat-treated at high temperatures for approximately two weeks, with a peak temperature of about 1,200 degrees Fahrenheit, to convert the niobium-tin wires into superconductor at operation temperatures. The team encased several coils in a strong innovative structure composed of an iron yoke with aluminum clamps and a stainless-steel skin to stabilize the coils against the huge electromagnetic forces that can deform the brittle coils, thus degrading the niobium-tin wires.

The Fermilab group took every known design feature into consideration, and it paid off.

“This is a tremendous achievement in a key enabling technology for circular colliders beyond the LHC,” said Soren Prestemon, a senior scientist at Berkeley Lab and director of the multilaboratory U.S. Magnet Development Program, which includes the Fermilab team. “This is an exceptional milestone for the international community that develops these magnets, and the result has been enthusiastically received by researchers who will use the beams from a future collider to push forward the frontiers of high-energy physics.”

And the Fermilab team is geared up to make their mark in the 15-tesla territory.

“There are so many variables to consider in designing a magnet like this: the field parameters, superconducting wire and cable, mechanical structure and its performance during assembly and operation, magnet technology, and magnet protection during operation,” Zlobin said. “All of these issues are even more important for magnets with record parameters.”

Over the next few months, the group plans to reinforce the coil’s mechanical support and then retest the magnet this fall. They expect to achieve the 15-tesla design goal.

And they’re setting their sights even higher for the future.

“Based on the success of this project and the lessons we learned, we’re planning to advance the field in niobium-tin magnets for future colliders to 17 teslas,” Zlobin said.

It doesn’t stop there. Zlobin says they may be able to design steering magnets that reach a field of 20 teslas using special inserts made of new advanced superconducting materials.

Call it a field goal.

The project is supported by the Department of Energy Office of Science. It is a key part of the U.S. Magnet Development Program, which includes Fermilab, Brookhaven National Laboratory, Lawrence Berkeley National Laboratory and the National High Magnetic Field Laboratory.

See other science results from Fermilab.

Neutrinos are among the most abundant particles in nature, yet very little is known about these mysterious particles and their role in the universe. Researchers think neutrinos might hold the key to understanding why matter exists and how an exploding star transitions into a black hole.

Now the Johannes Gutenberg University Mainz, Germany, which has conducted neutrino research for many years, has taken a significant step to participate in the next big neutrino experiment: the Deep Underground Neutrino Experiment, hosted by Fermi National Accelerator Laboratory in the United States. More than 1,000 scientists from over 30 countries are collaborating on DUNE.

The two institutions have announced that they have signed an agreement to jointly appoint an internationally renowned researcher who will strengthen the experimental particle physics research program at JGU Mainz and advance a German contribution to DUNE.

This is the first Fermilab joint agreement with a university in Germany.

“This success underlines, once again, the exceptional reputation of the PRISMA⁺ Cluster of Excellence at our university and the outstanding quality of research undertaken there, thus confirming the international standing of our physicists in Mainz,” states Prof. Georg Krausch, President of Johannes Gutenberg University Mainz.

JGU Mainz and other German research institutions already play major roles in international neutrino experiments, including IceCube, Borexino, and JUNO. In recent years, German scientists have shown interest in joining DUNE, and the DESY laboratory in Hamburg will host an international workshop on contributions to the DUNE near detector, to be installed at Fermilab, in October.

“Mainz University has a great tradition in particle physics,” said Fermilab Director Nigel Lockyer.  “We are very pleased to have a joint faculty position that will seed stronger ties between our institutions.”

DUNE will send neutrino and antineutrino beams 1,300 kilometers straight through the earth to find out whether neutrinos might be responsible for the dominance of matter over antimatter in our universe. The beams originate at the Fermilab particle accelerator complex near Chicago and will travel through dirt and rock — no tunnel needed — to the enormous particle detectors located 1.5 kilometers underground at the Sanford Underground Research Facility. Prep work is underway for the excavation of about 800,000 tons of rock to create the huge caverns for the DUNE far detectors.

Two “small” prototype detectors, each about the size of a three-story house, have been built at the European research center CERN, and the construction of components for the four full-size far detectors, each 20 times larger than one of the prototype detectors, will begin next year.

“We hope that the Mainz group will contribute their innovative detector concept to the DUNE near detector, which will allow us to analyze the neutrino beam at Fermilab before it goes through the earth,” said DUNE spokesperson Stefan Söldner-Rembold, University of Manchester, UK. “This is crucial for understanding the data the neutrinos produce when they arrive in South Dakota.”

The newly recruited neutrino scientist will be based in Mainz and become a member of the PRISMA+ Cluster of Excellence for precision physics, fundamental interactions and structure of matter. The appointed scientist also will have the opportunity for extended research stays at Fermilab.

How did you end up at Fermilab?

I’m from Georgia — a beautiful country in Eastern Europe, in the Caucasus Mountains. My husband, Guram Chlachidze, who also works at Fermilab, and I moved to the U.S. about 18 years ago. We were particle physicists, and my husband was invited as a guest scientist at Fermilab.

It was a difficult time in Georgia. It was the time after the Soviet Union was broken up, and the country was fighting for its independence. So, for us to receive this invitation for Guram to work at Fermilab was just super exciting.

What was it like when you arrived at Fermilab?

When we arrived in the U.S., my husband started working at Fermilab, and our daughter was born quite soon after, within a few months. I put my career on hold and adjusted to my new life.

I was a new mom in a new country, everything new. I spent about three years as a stay-at-home mom. Even though it was so challenging and so difficult, the people around were just super nice, and this was what gave me strength to stay in the U.S. and start our new life here.

We are citizens now. Even though we visit Georgia every year in the summer to see our parents, family and friends, we feel at home here. Fermilab is our home, and the U.S. is our country.

What is your role at Fermilab?

I am in charge of Lederman Science Center exhibit development, upgrade, operations and maintenance. These exhibits are about particle physics, developed for middle school students and the general public.

The challenge and excitement of this job is that you get to create a hands-on activity that communicates the complicated ideas of particle physics and makes them accessible and understandable for someone without any background in physics.

The work we are doing with these exhibits is trying to make a bridge between Fermilab science and the public — get people excited about particle physics.

Of course, we don’t expect to teach them physics in a few hours. That’s impossible. But we are hopeful that these exhibits will kick-start their interest in Fermilab science and STEM in general. This is what gives me motivation and makes me excited about my job.

What is your favorite part of your job?

Coming up with a new exhibit — brainstorming ideas about it and putting it together in my mind. Then I share it with the exhibit committee, and I get my colleagues’ feedback on it. We put together a prototype and, if everything works well, we build a new exhibit.

In the last five years, we’ve built and upgraded many exhibits; one of them is about gravitational lensing. I came up with this idea, and my friends liked it, so we put together a prototype. Then, I literally built it in my garage.

Currently, I’m working on a new exhibit about neutrino mass. This is a very challenging exhibit to put together because we know very little about neutrino masses — we only know upper limits for them.

Scientists don’t know at this point exactly what the three neutrino masses are. The exhibit will introduce our visitors to the mass scale of subatomic particles — where different particles fit on that scale and how Fermilab scientists use underground neutrino experiments to explore the neutrino mass mystery.

What do you like to do when you’re not at work?

Traveling is probably most fun for me beyond my work. We go to Georgia to see our family, and we usually stop somewhere in Europe to see places. This is something that really makes me happy.

I love remodeling at home, I change colors, relocate furniture; my husband doesn’t like this, but I do it anyway. I also love cooking and baking for my family.

Balloons can help make a space perfect for a party. Now they also can help when it comes to accelerating particles to near the speed of light.

The innovative use of balloons provides a new, patented way for engineers to shape the metal heart of particle accelerators.

Many particle accelerators use structures called cavities, which provide the kick needed to accelerate particles to higher and higher energies as the particles barrel through one after the other. Situated deep inside an accelerator and cooled by a shell containing liquid helium, cavities have to be just the right shape and size to boost particles to the desired energies. Even small differences in the shape of these metal chambers make large differences in the electric fields that are generated inside the cavities to push particles to greater speeds.

Faced with one particular cavity that was too misshaped to use and inaccessible because of its metal shell, Fermilab engineers Mohamed Hassan and Donato Passarelli got an idea: What if you could reshape a cavity without removing the surrounding shell? They went to work, developing an innovative process called balloon tuning.

“I hope balloon tuning is an example for the accelerator community — that we should think out of the box and not always stick with the standard and common technique,” said Passarelli.

The patented balloon tuning process is a new option in the suite of techniques used to prepare cavities before they’re installed in an accelerator.

Most acceleration cavities are a series of round, hollow cells that look like a giant strand of metal beads. Before any cavity is installed, it is carefully tested and tuned using an automated machine that grasps the edges of each cell to make small, precise adjustments: a little push here, a little stretch there. The process continues until the cavity is adjusted so that, once the cavity is up and running inside an accelerator, it’s in the shape to produce the perfect electric field to propel charged particles.

But before most cavities can be installed, they must also be fitted with a metal jacket so the cavity can be cooled to extremely low temperatures with liquid helium. After that, the only easy way to apply forces to the cells is to push or pull on the ends of the cavity, rather than targeting each cell individually. If a cavity becomes misshaped during or after the process of putting the jacket on, the traditional tuning method can’t be applied without cutting the metal jacket off — a laborious, time-consuming task.

Hassan and Passarelli started contemplating this challenge after an old test cavity deformed during a pressure test.

“After the pressure test, I was determined to find a way to fix this cavity and thought, ‘Why not access it from the inside, which is accessible even with a jacket?’” Hassan said.

The need to apply the force inside the cavities without scratching the inner surface or introducing unacceptable levels of contamination led them to using specially designed balloons made of rubberized nylon.

A pump fills each balloon with air until it applies about two bars of pressure — a little less than what’s recommended for standard car tires. This isn’t enough pressure to reshape a cavity cell on its own, but that pressure can be used to influence which cell deforms when forces are applied to the ends of a cavity at room temperature. Balloons let you single out a particular cell, either stretching or squeezing it.

If a particular cell needs to be stretched, a balloon inflated inside it provides an extra nudge for it to expand as the flanges are pulled apart. Whereas if a cell needs to be squeezed, a series of balloons can support all the other cells as the two ends are pushed together.

The engineers and their team demonstrated the concept by tuning an unjacketed cavity. Then they turned their attention to the misshaped cavity that had inspired them to develop the process. They succeeded in returning it to usable condition.

“Balloon tuning will be a nice additional tool for cavity production that can save quite a bit of money and time,” Hassan said.

High-performing cavities are crucial components in Fermilab’s upcoming PIP-II accelerator and SLAC National Accelerator Laboratory’s LCLS-II X-ray laser, and they are a major part of a current Fermilab project to extend the time that a qubit can maintain information.

The balloon-tuning technique was recently patented, speeding through the patent office in record time for Fermilab, said Aaron Sauers, the lab’s patent and licensing executive.

“Mohamed and Donato developed a truly beautiful method and apparatus to tune dressed cavities,” Sauers said. “I was excited to file the patent application on their invention.”

Hassan and Passarelli see automated balloon tuning as a possibility, which could make it as convenient to use as the current method is for unjacketed cavities. The technique may also find applications in other fields that use similar cavities.

“The hope is that people looking at this idea will get inspired and either adapt or use this technique in their own application,” Passarelli said.

The U.S. Department of Energy has awarded researchers at its Fermi National Accelerator Laboratory more than $3.5 million to boost research in the fast-emerging field of Quantum Information Science.

“Few pursuits have the revolutionary potential that quantum science presents,” said Fermilab Chief Research Officer Joe Lykken. “Fermilab’s expertise in quantum physics and cryogenic engineering is world-class, and combined with our experience in conventional computing and networks, we can advance quantum science in directions that not many other places can.”

As part of a number of grants to national laboratories and universities offered through its Quantum Information Science-Enabled Discovery (QuantISED) program, DOE’s recent round of funding to Fermilab covers three initiatives related to quantum science. It also funds Fermilab’s participation in a fourth initiative led by Argonne National Laboratory.

For a half-century, Fermilab researchers have closely studied the quantum realm and provided the computational and engineering capabilties needed to zoom in on nature at its most fundamental level. The projects announced by the Department of Energy will build on those capabilities, pushing quantum science and technology forward and leading to new discoveries that will enhance our picture of the universe at its smallest scale.

“Fermilab is well-versed in engineering, algorithmic development and recruiting massive computational resources to explore quantum-scale phenomena,” said Fermilab Head of Quantum Science Panagiotis Spentzouris. “Now we’re wrangling those competencies and capabilities to advance quantum science in many areas, and in a way that only a leading physics laboratory could.”

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The Fermilab-led initiatives funded through these DOE QuantISED grants are:

Large-scale simulations of quantum systems on high-performance computing with analytics for high-energy physics algorithms
Lead principal investigator: Adam Lyon, Fermilab

The large-scale simulation of quantum computers has plenty in common with simulations in high-energy physics: Both must sweep over a large number of variables. Both organize their inputs and outputs similarly. And in both cases, the simulation has to be analyzed and consolidated into results. Fermilab scientists, in collaboration with scientists at Argonne National Laboratory, will use tools from high-energy physics to produce and analyze simulations using high-performance computers at the Argonne Leadership Computing Facility. Specifically, they will simulate the operation of a qubit device that uses superconducting cavities (which are also used as components in particle accelerators) to maintain quantum information over a relatively long time. Their results will determine the device’s impact on high-energy physics algorithms using an Argonne-developed quantum simulator.

Partner institution: Argonne National Laboratory

Research technology for quantum information systems
Lead principal investigator: Gustavo Cancelo, Fermilab

One of the main challenges in quantum information science is designing an architecture that solves problems of massive interconnection, massive data processing and heat load. The electronics must be able to operate and interface with other electronics operating both at 4 kelvins and at near absolute zero. Fermilab scientists and engineers are designing novel electronic circuits as well as massive control and readout electronics to be compatible with quantum devices, such as sensors and quantum qubits. These circuits will enable many applications in the quantum information science field.

Partner institutions: Argonne National Laboratory, Massachusetts Institute of Technology, University of Chicago

MAGIS-100 – co-led by Stanford University and Fermilab
Lead Fermilab principal investigator: Rob Plunkett

Fermilab will host a new experiment to test quantum mechanics on macroscopic scales of space and time. Scientists on the MAGIS-100 experiment will drop clouds of ultracold atoms down a 100-meter-long vacuum pipe on the Fermilab site, and use a stable laser to create an atom interferometer which will look for dark matter made of ultralightweight particles. They will also advance a technique for gravitational-wave detection at relatively low frequencies.

This is a joint venture under the collaboration leadership of Stanford University Professor Jason Hogan, who is funded by grant GBMF7945 from the Gordon and Betty Moore Foundation. Rob Plunkett of Fermilab serves as the project manager.

Other participating institutions: Northern Illinois University, Northwestern University, Stanford University, Johns Hopkins University, University of Liverpool

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Fermilab was also funded to participate in another initiative led by Argonne National Laboratory:

Quantum sensors for widie-band axion dark matter detection
Lead principal investigator: Peter Barry, Argonne

Researchers are searching high and low for dark matter, the mysterious substance that makes up a quarter of our universe. One theory proposes that it could be made of particles called axions, which would signal their presence by converting into particles of light, called photons. Fermilab researchers are part of a team developing specialized detectors that look for photons in the terahertz range — at frequencies just below the infrared. The development of these detectors will widen the range of frequencies where axions may be discovered. To bring the faint signals to the fore, the team is using supersensitive quantum amplifiers.

Other participating institutions: National Institute of Standards and Technology, University of Colorado