Large Hadron Collider Begins Operations at CERN

Context

By the late 20th century, particle physicists had pushed the limits of existing accelerators in their efforts to probe the fundamental structure of matter. Facilities such as CERN's Large Electron-Positron Collider and Fermilab's Tevatron had confirmed key elements of the Standard Model but left open questions about the origins of mass and other phenomena that required collisions at far higher energies. CERN's member states approved the LHC project in the mid-1990s after the cancellation of the U.S. Superconducting Super Collider, shifting the focus of high-energy physics to Europe. Construction of the underground ring, which reuses the tunnel previously housing the LEP collider, involved thousands of scientists, engineers, and technicians from more than 60 countries working over more than a decade on superconducting magnets, cryogenic systems, and detectors.

What Happened

In the CERN Control Centre near Geneva on the morning of September 10, 2008, the operations team began injecting protons into the LHC ring in stages, advancing the beam three kilometers at a time. Under the direction of project leader Lyn Evans, the clockwise beam was successfully steered around the full 27-kilometer circumference and reached the control room monitors at 10:28 local time. A second beam was later circulated in the opposite direction. CERN Director-General Robert Aymar and international collaborators watched the milestone in real time, marking the end of years of assembly and testing for the machine that straddles the French-Swiss border.

Aftermath

The successful first circulation prompted immediate celebrations and further commissioning work, but nine days later a faulty electrical connection caused a magnet quench that damaged dozens of superconducting magnets and released helium into the tunnel. Repairs and safety reviews delayed full operations until late 2009. The incident led to design improvements and reinforced safety protocols across the accelerator complex.

Legacy

The LHC's startup established a new benchmark for international scientific collaboration and accelerator engineering, enabling the 2012 discovery of the Higgs boson that completed the Standard Model. It has since produced extensive data on heavy-ion collisions and rare particle decays while continuing searches for physics beyond the Standard Model. The project demonstrated the feasibility of sustained global investment in fundamental research and influenced planning for future colliders.