Thanks to recent upgrades to the Main Injector, Fermilab’s flagship accelerator, Fermilab scientists have produced 700-kilowatt proton beams for the lab’s experiments. Photo: Peter Ginter
Fermilab’s accelerator is now delivering more neutrinos to experiments than ever before.
The U.S. Department of Energy’s Fermi National Accelerator Laboratory has achieved a significant milestone for proton beam power. On Jan. 24, the laboratory’s flagship particle accelerator delivered a 700-kilowatt proton beam over one hour at an energy of 120 billion electronvolts.
The Main Injector accelerator provides a massive number of protons to create particles called neutrinos, elusive particles that influence how our universe has evolved. Neutrinos are the second-most abundant matter particles in our universe. Trillions pass through us every second without leaving a trace.
Because they are so abundant, neutrinos can influence all kinds of processes, such as the formation of galaxies or supernovae. Neutrinos might also be the key to uncovering why there is more matter than antimatter in our universe. They might be one of the most valuable players in the history of our universe, but they are hard to capture and this makes them difficult to study.
“We push always for higher and higher beam powers at accelerators, and we are lucky our accelerator colleagues live for a challenge,” said Steve Brice, head of Fermilab’s Neutrino Division. “Every neutrino is an opportunity to study our universe further.”
With more beam power, scientists can provide more neutrinos in a given amount of time. At Fermilab, that means more opportunities to study these subtle particles at the lab’s three major neutrino experiments: MicroBooNE, MINERvA and NOvA.
“Neutrino experiments ask for the world, if they can get it. And they should,” said Dave Capista, accelerator scientist at Fermilab. Even higher beam powers will be needed for the future international Deep Underground Neutrino Experiment, to be hosted by Fermilab. DUNE, along with its supporting Long-Baseline Neutrino Facility, is the largest new project being undertaken in particle physics anywhere in the world since the Large Hadron Collider.
“It’s a negotiation process: What is the highest beam power we can reasonably achieve while keeping the machine stable, and how much would that benefit the neutrino researcher compared to what they had before?” said Fermilab accelerator scientist Mary Convery.
“This step-by-step journey was a technical challenge and also tested our understanding of the physics of high-intensity beams,” said Fermilab Chief Accelerator Officer Sergei Nagaitsev. “But by reaching this ambitious goal, we show how great the team of physicists, engineers, technicians and everyone else involved is.” The 700-kilowatt beam power was the goal declared for 2017 for Fermilab’s accelerator-based experimental program.
Particle accelerators are complex machines with many different parts that change and influence the particle beam constantly. One challenge with high-intensity beams is that they are relatively large and hard to handle. Particles in accelerators travel in groups referred to as bunches.
Roughly one hundred billion protons are in one bunch, and they need their space. The beam pipes – through which particles travel inside the accelerator – need to be big enough for the bunches to fit. Otherwise particles will scrape the inner surface of the pipes and get lost in the equipment.
The Main Injector, a 2-mile-circumference racetrack for protons, is the most powerful particle accelerator in operation at Fermilab. It provides proton beams for various particle physics experiments as well as Fermilab Test Beam Facility. Photo: Reidar Hahn
Such losses, as they’re called, need to be controlled, so while working on creating the conditions to generate a high-power beam, scientists also study where particles get lost and how it happens. They perform a number of engineering feats that allow them to catch the wandering particles before they damage something important in the accelerator tunnel.
To generate high-power beams, the scientists and engineers at Fermilab use two accelerators in parallel. The Main Injector is the driver: It accelerates protons and subsequently smashes them into a target to create neutrinos. Even before the protons enter the Main Injector, they are prepared in the Recycler.
The Fermilab accelerator complex can’t create big bunches from the get-go, so scientists create the big bunches by merging two smaller bunches in the Recycler. A small bunch of protons is sent into the Recycler, where it waits until the next small bunch is sent in to join it. Imagine a small herd of cattle, and then acquiring a new herd of the same size. Rather than caring for them separately, you allow the two herds to join each other on the big meadow to form a big herd. Now you can handle them as one herd instead of two.
In this way Fermilab scientists double the number of particles in one bunch. The big bunches then go into the Main Injector for acceleration. This technique to increase the number of protons in each bunch had been used before in the Main Injector, but now the Recycler has been upgraded to be able to handle the process as well.
“The real bonus is having two machines doing the job,” said Ioanis Kourbanis, who led the upgrade effort. “Before we had the Recycler merging the bunches, the Main Injector handled the merging process, and this was time consuming. Now, we can accelerate the already merged bunches in the Main Injector and meanwhile prepare the next group in the Recycler. This is the key to higher beam powers and more neutrinos.”
Fermilab scientists and engineers were able to marry two advantages of the proton acceleration technique to generate the desired truckloads of neutrinos: increase the numbers of protons in each bunch and decrease the delivery time of those proton to create neutrinos.
“Attaining this promised power is an achievement of the whole laboratory,” Nagaitsev said. “It is shared with all who have supported this journey.”
The new heights will open many doors for the experiments, but no one will rest long on their laurels. The journey for high beam power continues, and new plans for even more beam power are already under way.
Editor’s note: Learn about the laboratory’s birthday events, view a historical timeline and see photographs taken throughout the laboratory’s 50th year on the Fermilab 50th anniversary website.
Fermilab is turning 50! So how did it all start?
Fermilab — originally called the National Accelerator Laboratory — began operations in Illinois on June 15, 1967. The lab was built on 6,800 acres of land near the town of Batavia, Illinois, on a site that included the buildings of a small housing development named Weston. Fermilab’s first big machine, a particle accelerator about four miles in circumference called the Main Ring, paved the way to the construction of the world’s most powerful particle collider, the Tevatron. The original Main Ring was designed to collide particles at what was then a staggering 200 billion electronvolts of energy. The possibility of achieving that high energy was the driving reason for creating the National Accelerator Laboratory.
Today Fermilab is one of 17 national laboratories of the U.S. Department of Energy. It is America’s premier laboratory for particle physics research and houses seven particle accelerators that provide beam for numerous experiments and R&D projects. It is the future home of the Long-Baseline Neutrino Facility, which will power the world’s biggest neutrino experiment, the Deep Underground Neutrino Experiment.
“While Fermilab and the field of high-energy physics have changed and evolved since its 1967 founding, the dedication and imagination of the staff and the user community in answering ever deeper and broader questions have remained as strong as ever,” said Adrienne Kolb, who served as Fermilab archivist and historian from 1983 to 2015.
On June 15, 1967, Robert Wilson and 17 other employees of NAL, AEC and DUSAF (the architectural and engineering firm responsible for much of the early construction at Fermilab) began their work in Illinois, the date that Wilson later considered to be laboratory’s birthday. While the Weston houses were prepared for hosting offices and work space for the new lab, Wilson and his team rented offices on the 10th floor of the Oak Brook Executive Plaza tower in Oak Brook, Illinois.
“The first year was very colored by that — that office building was the lab, the place that we went to every day to do what we were doing,” said Lincoln Read, a physicist who worked at the laboratory from 1967 to 2004.
The building was selected for its convenient location between Weston and O’Hare International Airport and gave these pioneers an unobstructed view of the Illinois farmland west of Oak Brook.
In January 1968, the NAL staff finished a new design report partially based on the Berkeley design study that laid out the plan for the laboratory. They moved to the Weston site during September 1968, and the lab broke ground for its first accelerator on Dec. 1, 1968.
“As a small but growing staff, together we all put together a concept design of the facilities and its accelerators,” Read said. “We knew the work we were doing was important, and that became part of the spirit of the place.”
In early 1971, Wilson told the laboratory’s Users’ Organization that “one of the first aims of experiments on the NAL accelerator system will be the detection of a neutrino. I feel that we then will be in business to do experiments on our accelerator.” Later that year experiment E-21, named “Neutrino Physics at Very High Energies” and run by a Caltech group, was the first to detect neutrinos at the new laboratory.
The centerpiece of the emerging accelerator complex was called the Main Ring. The machine reached scientists’ energy goal — 200-billion-electronvolt particle beams — in 1972, four years after completing the accelerator’s design. Thanks to several technological breakthroughs, the laboratory was able to make upgrades and continually increase the beam energy, achieving world record collision energies of nearly 2 trillion electronvolts, or TeV, in 1986. The TeV energy range gave the accelerator in the Main Ring tunnel its new name: the Tevatron.
Today, Fermilab is known for its world-leading accelerator-based neutrino research program, the development and construction of particle accelerators, its contributions to research at the Large Hadron Collider and its particle astrophysics program.
“The quest to understand the universe goes on and beckons us as Fermilab celebrates this 50th anniversary milestone,” Kolb said.
Fermilab now employs about 1,800 employees and represents the second-largest particle accelerator laboratory in the world. Approximately 4,000 scientists from 44 countries use Fermilab and its particle accelerators, detectors and computers for their research. They contribute to the lab’s numerous physics experiments, keeping the United States at the leading edge of the international field of particle physics.
On May 11, 1974, National Accelerator Laboratory was given a new name: Fermi National Accelerator Laboratory. The eponym honors famed Italian physicist Enrico Fermi, whose accomplishments in both theoretical and experimental physics place him among the greatest scientists of the 20th century.
Many visitors to Fermilab reasonably conclude from its name that Enrico Fermi worked at the laboratory, but he never did. In fact, he died in 1954, years before scientists even officially recommended the construction of a U.S. accelerator laboratory in 1963.
In 1938, Fermi won the Nobel Prize for work that eventually led to the first controlled release of nuclear energy. He and his family then left Italy and came to the United States, where he accepted a position at Columbia University. He later moved to the University of Chicago, where he built the first atomic pile in the squash court under the university’s Stagg Field. While there, he continued investigating the nature of particles that make up the nucleus. He was also active in the design of the school’s synchrocyclotron. At the time of its completion, it was one of the most powerful atom smashers in the world.
Fermi was also responsible for giving the neutrino its name.
So why was National Accelerator Laboratory named after Enrico Fermi? In announcing the eventual name change, Atomic Energy Commission Chair Glenn T. Seaborg cited Fermi’s contributions to the welfare of the United States, his singular achievements to nuclear physics and his scientific successes at the nearby University of Chicago.
It is particularly fitting that we honor Dr. Fermi in this manner, for in so doing we further acknowledge his many contributions to the progress of nuclear science, particularly his work on nuclear processes. Enrico Fermi was a physicist of great renown who contributed in a most significant way to the defense and welfare of his adopted land and to the enhancement of its intellectual well-being. His greatest achievement, the first sustained nuclear chain reaction, took place in a small laboratory in Chicago. It seems singularly appropriate, therefore, that the federal government recognize the memory of a man who was at the forefront of science in his day by naming in his honor a laboratory near Chicago — a laboratory which will have a major international impact on our understanding of the basic structure of matter.
You can read more about Fermi’s numerous and important contributions to science in the Fermilab History and Archives website. Several articles on the dedication of the lab as Fermi National Accelerator Laboratory can be found there as well.
Twinkle, twinkle, little supernova