A new way to study high-energy gamma rays

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

The CMS experiment at CERN’s Large Hadron Collider has achieved yet another significant milestone in its already storied history as a leader in the field of high-energy experimental particle physics. The U.S. contingent of the CMS collaboration, known as USCMS and managed by Fermilab, has been granted the Department of Energy’s final Critical Decision- 4 approval for its multiyear Phase 1 Detector Upgrade program, formally signifying the completion of the project after having met every stated goal — on time and under budget.

“Getting CD-4 approval is a tremendous vote of confidence for the many people involved in CMS,” said Fermilab scientist Steve Nahn, U.S. project manager for the CMS detector upgrade. “The LHC is the best tool we have for further explication of the particle nature of the universe, and there are still mysteries to solve, so we have to have the best apparatus we can to continue the exploration.”

The CMS experiment is a generation-spanning effort to build, operate and upgrade a particle-detecting behemoth that observes its protean prey in a large but cramped cavern 300 feet beneath the French countryside. CMS is one of four large experiments situated along the LHC accelerator complex, operated by CERN in Geneva, Switzerland. The LHC is a 17-mile-round ring of magnets that accelerates two beams of protons in opposite directions, each to 99.999999999% the speed of light, and forces them to collide at the centers of CMS and the LHC’s other experiments: ALICE, LHCb and ATLAS.

The main goal of CMS (and the other LHC experiments) is to keep track of which particles emerge from the rapture of pure energy created from the collisions in order to search for new particles and phenomena. In catching sight of such new phenomena, scientists aim to answer some of the most fundamental questions we have about how the universe works.

The global CMS collaboration comprises more than 5,000 professionals — including roughly 1,000 students — from over 200 institutes and universities across more than 50 countries. This international team collaborates to design, build, commission and operate the CMS detector, whose data is then distributed to dedicated centers in 40 nations for analysis. And analysis is their raison d’etre. By sussing out patterns in the data, CMS scientists search for previously unseen or unconfirmed phenomena and measure the properties of elementary particles that make up the universe with greater precision. To date, CMS has published over 900 papers.

The USCMS collaboration is the single largest national group in CMS, involving 51 American universities and institutions in 24 states and Puerto Rico, over 400 Ph.D. physicists, and more than 200 graduate students and other professionals. USCMS has played a primary role in much of the CMS experiment’s original design and construction, including a wide network of eight CMS computing centers located across the United States, and in the experiment’s data analysis. USCMS is supported by the U.S. Department of Energy and the National Science Foundation and has played an integral role in the success of the CMS collaboration as a whole from its founding.

The CMS experiment, the LHC and the other LHC experiments became operational in 2009 (17 years after the CMS letter of intent), beginning a 10-year data-taking period referred to as Phase 1.

Phase 1 was divided into four major epochs, alternating two periods of data-taking with two periods of maintenance and upgrade operations. The two data-taking periods are referred to as Run 1 (2009-2013) and Run 2 (2015-2018). It was during Run 1 (in 2012) that the CMS and ATLAS collaborations jointly announced they each had observed the long predicted Higgs boson, resulting in a Nobel Prize awarded a year later to scientists Peter Higgs and François Englert, and a further testament to the strength of the Standard Model of particle physics, the theory within which the Higgs boson was first hypothesized in 1964.

“That prize was a historic triumph of every individual, institution and nation involved with the LHC project, not only validating the Higgs conjecture, a cornerstone of the Standard Model, but also giving science a new particle to use as a tool for further exploration,” Nahn said. “This discovery and every milestone CMS has achieved since then is encouragement to continue working toward further discovery. That goes for our latest approval milestone.”

During the entirety of Phase 1, the wizard-like LHC particle accelerator experts were continually ramping up the collision energy and intensity, or in particle physics parlance, the luminosity of the LHC beam. The CMS technical team was charged with fulfilling the Phase 1 Upgrade plan, a series of hardware upgrades to the detector that allowed it to fully profit from the gains the LHC team was providing.

While the LHC accelerator folks were prepping to push 20 times as many particles through the experiments per second, the experiments were busy upgrading their systems to handle this major influx of particles and the resulting data. This meant updating many of the readout electronics with faster and more capable brains to manage and process the data produced by CMS.

With support from the Department of Energy’s Office of Science and the National Science Foundation, USCMS implemented $40 million worth of these strategic upgrades on time and under budget.

With these upgrades complete, the CMS detector is now ready for LHC Run 3, which will go from 2021-23, and the collaboration is starting the stage of data taking on a solid foundation.

Still, USCMS isn’t taking a break: The collaboration is already gearing up for its next, even more ambitious set of upgrades, planned for installation after Run 3. This USCMS upgrade phase will prepare the detector for an even higher luminosity, resulting in a data set 10 times greater than what the LHC provides currently.

Every advance in the CMS detector ensures that it will support the experiment through 2038, when the LHC is planned to complete its final run.

“For the last decade, we’ve worked to improve and enhance the CMS detector to squeeze everything we can out of the LHC’s collisions,” Nahn said. “We’re prepared to do the same for the next two decades to come.”

It was a three-hour nighttime road trip that capped off a journey begun seven years ago.

From about 12:30-3 a.m. on Friday, Aug. 16, the first major superconducting section of a particle accelerator that will power the biggest neutrino experiment in the world made its way along a series of Chicagoland roadways at a deliberate 10 miles per hour.

Hauled on a special carrier created just for its 25-mile journey, at 3:07 a.m. the nine-ton structure pulled into its permanent home at the Department of Energy’s Fermilab. It arrived from nearby Argonne National Laboratory, also a DOE national laboratory.

The high-tech component is the first completed cryomodule for the PIP-II particle accelerator, a powerful machine that will become the heart of Fermilab’s accelerator complex. The accelerator will generate high-power beams of protons, which will in turn produce the world’s most powerful neutrino beam, for the international, Fermilab-hosted Deep Underground Neutrino Experiment. It will also provide for the long-term future of the Fermilab research program.

PIP-II is the first particle accelerator project in the United States with significant international contribution, with cavities and cryomodules built in France, India, Italy, the United Kingdom and the United States.

The cryomodule effort at Argonne began in 2012. Scientists and engineers at Argonne led its design, working with a Fermilab team. The Argonne group also built the cryomodule, tested its subcomponents and assembled it, evolving a design used in one of Argonne’s particle accelerators.

And now it’s arrived.

“There is a profound significance in the arrival of the first PIP-II cryomodule: it ushers in a new era for the Fermilab accelerator complex, the era of superconducting radio-frequency acceleration,” said Fermilab PIP-II Project Director Lia Merminga.

The PIP-II accelerator blueprint

A cryomodule is the major unit of a particle accelerator. Like the cars of a train, cryomodules are hitched together end-to-end. The PIP-II linear accelerator will comprise 23 of them, adding up to a roughly 200-meter, near-light-speed runway for powerful protons.

Very powerful protons. The new accelerator will enable a 1.2-megawatt proton beam for the lab’s experiments. That’s 60% more power than the lab’s current accelerator chain can provide.

And it’s put together one cryomodule at a time. Each houses a string of superconducting acceleration cavities. These shiny metal tubes impart energy to the beam, and they too are placed end-to-end. As the proton beam shoots through one cavity after the next, it picks up energy, thanks to the electromagnetic fields inside the cavities, propelling the beam forward.

By the time the beam exits the final cavity of the last PIP-II cryomodule, it will have gained 800 million electronvolts of energy and travel at 84% of the speed of light.

Then it’s really off to the races: After the beam leaves the PIP-II linac, it will continue down any of a number of paths, charging through Fermilab’s accelerators and eventually smashing into a block of material. The resulting shower of particles will be sorted and routed to various experiments, where scientists study these morsels of matter to better understand how our universe operates at its most fundamental level.

The 60% boost in PIP-II power  — with the potential to increase power into the multimegawatt range at a later time — will provide more particles for scientists to study, accelerating the path to discovery.

The PIP-II accelerator is expected to be integrated into the Fermilab accelerator complex in 2026.

Riding the half-wave

The Argonne-designed PIP-II cryomodule contains eight accelerating cavities that look like big balloon bow ties. They’re a special type, called half-wave resonators. (“Half-wave,” because the profile of the electromagnetic field inside it resembles half of a standing wave.)

The half-wave resonator cryomodule will be first in the line of 23 and the only one of its kind at PIP-II.

The job of the half-wave resonator cryomodule is to get the beam going almost as soon as it comes out of the gate, taking it from 2 to 10 million electronvolts. Each cryomodule after that takes its turn ramping up the beam to its final energy of 800 million electronvolts.

Its design is based on those used in Argonne’s ATLAS particle accelerator, which accelerates heavy ions for nuclear physics research.

The PIP-II version features a few improvements. For one, the cavity performance is top-notch, thanks to advances in acceleration technology. The cavities are made of superconducting niobium. Refinements over the past decade in both niobium treatment and cavity manufacture have made it possible for PIP-II cavities to kick the beam to higher energies over shorter distances compared to ATLAS and other comparable cavities. They’re also more energy-efficient.

“We’re proud of the cavities we’ve built and their performance,” said Argonne physicist Zack Conway, who led the effort to build the cavities. “They’re truly world-leading.”

The cryomodule keeps the cavities at a cool 2 kelvins, or minus 270 degrees Celsius. Niobium superconducts at 9.2 K, but its performance soars at 2 K. Advanced cryogenics (the “cryo” in cryomodule) ensure that the PIP-II cavities maintain their chill temperature.

The result is a high-performance vehicle for beam.

“It’s been good to collaborate with one of our sister labs,” said Fermilab scientist Joe Ozelis, who oversees the cryomodule project. “This model of collaborative effort with our partners is key to the continued future success of PIP-II. It’s gratifying to now know that it can indeed work.”

Time to test

The recently arrived cryomodule has a way to go before it will be permanently installed as part of the PIP-II linear accelerator. For the next several months, Fermilab’s PIP-II group will perform a series of tests to make sure it meets specifications. Then, next year, a Fermilab group will test it with beam, putting the cryomodule through its paces.

“The first of anything in a project like this is always exciting, but there’s more to this for me personally,” said Genfa Wu, Fermilab physicist and a PIP-II SRF and cryogenics system manager. “This is the first low-beta superconducting cryomodule I’ll get to test in my professional experience.”

It’s also an initial run-through for the PIP-II cryomodule collaboration more generally. Twenty-two cryomodules are yet to be built and tested at Fermilab, of which 15 will arrive from outside the United States, including one prototype.

“PIP-II is an international collaboration,” Wu said. “We’re actively working with our international partners to make sure all the cryomodules work together.”

 

Partners in global science

PIP-II’s internationality reflects the biggest experiment it will power, the Deep Underground Neutrino Experiment, supported by the Long-Baseline Neutrino Facility at Fermilab. The flagship science project aims to unlock the mysteries of neutrinos, subtle particles that may carry the imprint of the universe’s beginnings.

Protons from the PIP-II beam will produce a beam of neutrinos, which will be sent 800 miles straight through Earth’s crust from Fermilab to particle detectors located a mile underground at the Sanford Underground Research Facility in South Dakota. DUNE scientists will study how the neutrinos change over that long distance. Their findings aim to tell us why we live in a universe dominated by matter.

More than 1,000 scientists from dozens of countries participate in LBNF/DUNE, which will start in the mid-2020s. It’s a global project with the ambitious research goals to match. And four of the LBNF/DUNE international partners also contribute to PIP-II. For the United States, the international nature of the PIP-II project is a new way of building large accelerator projects.

“The half-wave resonator cryomodule is a stellar example of how DOE labs work together to execute major projects that involve technological aptitude that no single lab has by itself,” Merminga said. “By leveraging Argonne’s experience in half-wave resonator technology, Fermilab is taking a major step in realizing its future while paving the road for even more collaboration. Exactly the same principle applies to our international partnerships, making PIP-II a very powerful new paradigm for future accelerator projects.”

And in some ways, it is all starting to come together when a truck with a huge, high-tech metal container rolls down a street in the middle of the night.

“The collaboration between has been very smooth, from design through fabrication,” Conway said. “That’s been wonderful.”

It pays dividends in other dimensions, too.

“We’ve learned so much from this for future collaborations, and those lessons are going to be vital for the linac project as a whole,” Ozelis said. “This is more than institutional. It’s a human endeavor as well.”

This work is supported by the Department of Energy Office of Science.