Scientists have restarted the world's largest particle accelerator after a more than three-year break to conduct upgrade and maintenance work.

The Large Hadron Collider (LHC) , located near Geneva, is perhaps best known for helping confirm the subatomic Higgs boson in 2012.

The European Organization for Nuclear Research (CERN) announced the restart on Friday, saying that "two beams of protons circulated in opposite directions around the Large Hadron Collider's 27-kilometer (16.8-mile) ring."

What is the Large Hadron Collider?

The LHC allows researchers to study the "dark universe" — the subatomic particles that make up some 96% of matter in the known universe, along with the forces that hold them together.

The particle accelerator consists of a ring of superconducting magnets which direct beams of energy around a circular route. The particles travel at high speeds in opposite directions and are made to collide into one another.

In 2012, the LHC allowed scientists to confirm a particle consistent with the Higgs boson particle, nicknamed the "God particle."

The experiments are taking place more than 100 meters (330 feet) under the border area of Switzerland and France.

Scientists are expecting to conduct an unprecedented number of collisions and hope to make a series of groundbreaking discoveries.

The LHC was shut down in December 2018 to allow for upgrade work to take place.

"The LHC itself has undergone an extensive consolidation program and will now operate at an even higher energy," said CERN's Director for Accelerators and Technology, Mike Lamont, adding that "it will deliver significantly more data."

kb/nm (AFP, AP)