Accelerator History

Fermilab is America's particle physics and accelerator laboratory. The lab's accelerators have always been among the best in the world, from the Main Ring and the Tevatron to the Main Injector and beyond. Since 1972, these complex instruments have allowed scientists from all over the world to explore fundamental questions about matter. You can learn about the history of the machines that make much of Fermilab's scientific work possible on this page.

This page contains curated collections of articles, primarily taken from Fermilab employee newsletters. Remember that these articles are reproduced directly from the original lab publications and reflect the state of the lab and scientific knowledge at the times they were written. Check the dates on the articles to place them in their proper context.


The pre-accelerator is the location where Fermilab's beam begins. The lab's first pre-accelerators were Cockcroft-Walton generators. The first one arrived from Switzerland in the fall of 1969. The lab added an additional Cockcroft-Walton generator in October 1977 and replaced the original Cockcroft-Walton with a new one in the summer of 1979. The Cockcroft-Waltons were replaced by an RFQ (Radio Frequency Quadrupole) in October 2012.


Fermilab's original linear accelerator, also called the Linac, is a roughly 500-foot straight accelerator that provides proton beam to the rest of the lab's chain of accelerators. The groundbreaking for the Linac was on December 1, 1968 and it achieved its design energy of 200 MeV exactly two years later, on December 1, 1970. Fermilab upgraded the Linac in the early 1990's, achieving its new design energy of 400 MeV on September 4, 1993. On March 15, 2019, the lab broke ground on PIP-II (originally called Project X), a new superconducting, 800 MeV linac that will replace the original linac.


Proton beams enter the Fermilab Booster from the Linac, accelerating through its roughly 1,500-foot-circumference ring to an energy of 8 GeV. The lab completed construction of the Booster on December 21, 1970. The Booster achieved its design energy of 8 GeV on May 21, 1971.

Main Ring

The Main Ring was Fermilab's first primary accelerator, the final and largest component of the lab's accelerator system. This underground ring, which was about four miles around, used magnets to accelerate protons to very high speeds. These protons, and other beams derived from them, were then used in the four experimental areas. The lab broke ground on the Main Ring tunnel on October 3, 1969 and installed the last Main Ring magnet on April 16, 1971. It achieved its initial design energy of 200 GeV on March 1, 1972, ahead of schedule and under budget. It quickly surpassed that energy goal, reaching 300 GeV on July 16, 1972, and 500 GeV on May 14, 1976. It was later used as a proton injector for the Tevatron accelerator, until it was replaced by the Main Injector in 1999.

Beam Controls

Delivering the beam from Fermilab’s accelerators to experiments requires careful control and monitoring by skilled people and sophisticated instruments.

Main Ring Transition to Energy Doubler/Saver

As early as the summer of 1967, lab director Robert Wilson had talked about the possibility of one day upgrading the accelerator complex with a more powerful superconducting accelerator and introducing a colliding beams program. This project was originally called the Energy Doubler, but later was also known as the Energy Saver. Ultimately, the superconducting proton-antiproton accelerator and collider the lab built would be known as the Tevatron. Building the Tevatron took years of planning, design, and construction.


The design effort for the Tevatron, originally known as the Energy Doubler, officially began in September 1972. The Department of Energy authorized construction of this superconducting accelerator on July 5, 1979. It would be installed in the Main Ring tunnel, beneath the Main Ring accelerator. The lab put the final Tevatron magnet in place on March 18, 1983, and the Tevatron achieved a world-record energy of 512 GeV on July 3 of that year. Meanwhile, the lab had begun work on the design for the Antiproton Source, a key part of the planned proton-antiproton collider aspect of the Tevatron, in 1981. The Antiproton Source was completed in 1985, and the first antiprotons circulated around the Tevatron on October 12, 1985. When it was complete, the Tevatron could deliver beams of protons to the fixed target experimental areas or collide the beam of protons with a beam of antiprotons traveling in the opposite direction. These collisions were observed by Fermilab’s experiments CDF and DZero.

Originally, the Main Ring delivered protons to the Tevatron. Fermilab upgraded its accelerator complex by replacing the Main Ring with the Main Injector, which began delivering protons to the Tevatron in 1999. At its peak, the Tevatron could produce particle collisions with energies of over 2 TeV. The lab shut down the Tevatron on September 30, 2011.

Main Injector

Fermilab originally constructed the Main Injector, a proton accelerator two miles in circumference, to replace the Main Ring as a proton injector for the Tevatron. The lab broke ground on the Main Injector on March 22, 1993. It was dedicated on June 1, 1999. As part of the Main Injector project, Fermilab also built the Recycler, a proton and antiproton storage ring, in the same tunnel as the Main Injector. After the Tevatron was shut down in 2011, the Main Injector’s proton beam was used to produce intense neutrino beams and muon beams for Fermilab experiments.


Fermilab's NuMI (Neutrinos at the Main Injector) is a set of facilities that use the lab's Main Injector to produce an intense beam of neutrinos. The construction of NuMI allowed the lab to begin conducting long-baseline neutrino experiments like MINOS, NOvA, and DUNE. The first funds for NuMI were allocated in 1997 and the lab held the NuMI groundbreaking ceremony on May 31, 2000. NuMI received its first beam from the Main Injector on December 3, 2004.