This Day in History — The Large Hadron Collider Circulates Its First Proton Beam

The Off-Key Bard descends beneath the French-Swiss countryside, where a 17-mile ring of superconducting magnets is preparing to send particles racing at nearly the speed of light.

"To understand some of the smallest things in existence, scientists built one of the largest and most complicated machines humanity has ever created."

On this day in 2008, at 10:28 AM local time near Geneva, Switzerland, scientists at CERN's control room watched a spot of light travel around a monitor display — a signal representing a beam of protons making its first complete circuit of the Large Hadron Collider. The room broke into applause. Eighteen years of planning, a decade of construction, and contributions from thousands of scientists and engineers in more than 100 countries had produced a machine capable of recreating conditions that existed fractions of a second after the Big Bang. At 10:28 on a Tuesday morning, it worked.

Later that same day, a second beam was successfully circulated in the opposite direction.

The Machine

The LHC occupies a circular tunnel 27 kilometers in circumference — roughly 17 miles — buried between 50 and 175 meters beneath the border of France and Switzerland. Inside run two parallel vacuum pipes, each thinner than a human hair in terms of the beam they carry, enclosed within superconducting magnets that must be kept at 1.9 Kelvin — about −271.3°C, or −456.3°F — colder than the background temperature of outer space. The cooling system required for those magnets contains more liquid helium than any other installation in the world.

At full operational energy, protons in the LHC travel at 99.9999991 percent of the speed of light, completing 11,245 full orbits of the 27-kilometer ring every second. The entire beam — which is thinner than a human hair — carries roughly the kinetic energy of a high-speed train. When two beams traveling in opposite directions are brought into collision, the energy concentrated in each impact point recreates temperatures more than 100,000 times hotter than the center of the Sun.

The particle detectors surrounding those collision points are themselves extraordinary constructions. The ATLAS detector is 46 meters long, 25 meters in diameter, and weighs 7,000 tonnes — built with a precision measured in micrometers. The CMS detector, more compact at 15 meters in diameter, weighs 14,000 tonnes. Both were assembled in underground caverns that had to be excavated to accommodate them.

Nine Days Later

The celebration of September 10 was brief. On September 19, 2008, nine days after the first beam was circulated, an electrical fault in a connection between two superconducting magnets caused a resistive zone — a "quench" — that rapidly heated. The heating vaporized a section of the liquid helium cooling system and released approximately six tonnes of liquid helium into the tunnel. Fifty-three magnets were damaged. The LHC was shut down for repairs.

The incident was serious, expensive, and deeply frustrating for everyone who had worked on the machine. It required over a year of repair work and system upgrades, including the installation of a new quench protection system designed to detect and respond to electrical faults faster. The LHC restarted in November 2009 and began sustained high-energy proton-proton collisions in March 2010.

The Higgs Boson

The machine's most celebrated achievement came on July 4, 2012, when the ATLAS and CMS collaborations jointly announced the discovery of a new particle consistent with the long-predicted Higgs boson. The Higgs particle is the observable excitation of the Higgs field — an invisible field permeating all of space that gives elementary particles their mass. Without it, electrons and quarks would be massless, atoms could not form, and chemistry as we know it would not exist.

The prediction that such a particle must exist had been made in 1964 by François Englert, Robert Brout, and Peter Higgs, among others. The LHC confirmed it 48 years later. Englert and Higgs shared the 2013 Nobel Prize in Physics.

What It Continues to Do

The Higgs was never the only goal. The LHC operates as an ongoing instrument for investigating:

Quark-gluon plasma: The state of matter that existed microseconds after the Big Bang, studied through heavy-ion collisions.

Matter-antimatter asymmetry: Why the universe contains more matter than antimatter — a question whose answer is not yet in the Standard Model.

Dark matter candidates: Particles that might explain the gravitational effects attributed to dark matter, if they can be produced in collisions and detected.

Physics beyond the Standard Model: Signatures of supersymmetry, extra dimensions, or other theoretical frameworks that could explain what the current model leaves unresolved.

The LHC has undergone multiple upgrade phases since 2008 and continues to set records for collision energy. It remains, 18 years after its first beam, the most powerful particle collider ever built.

There is something almost wonderfully paradoxical about the entire enterprise. To study the smallest things that exist — particles far too small to see, too fleeting to hold — humanity built one of the largest and most precisely engineered machines in its history, buried it underground along a national border, operated it at temperatures colder than outer space, and smashed invisible particles together at nearly the speed of light.

"Beneath the fields the protons race,
To probe the laws of time and space.
A giant ring was built to see,
The smallest pieces that can be."

History reminds us: the greatest discoveries often require building instruments on a monumental scale — not to look outward toward distant galaxies, but to illuminate the fundamental architecture of reality that underlies everything we can see.

Sources

• LHC First Beam — CERN — CERN
• Large Hadron Collider — Wikipedia — Wikipedia
• Discovery of the Higgs Boson — CERN — CERN
• LHC Incident of September 19, 2008 — CERN — CERN Document Server