The world's biggest particle accelerator, the Large Hadron Collider, is in operation again after more than a year of repairs.
The European Organisation for Nuclear Research, Cern, said in a statement on Friday that particle beams are once again circulating in the LHC, and that a clockwise circulating beam was established at 10 PM local time.
According to the Cern Twitter feed, an anticlockwise beam was also successfully injected, and both beams have completed many thousands of turns of the LHC.
"The LHC is up and running regularly. Operators are adjusting and testing obedient beams," according to the Cern Twitter feed.
The particle accelerator, which is in an underground location spanning the French-Swiss border, was started up for the first time in September 2008. However, it was decommissioned after only nine days in operation because a fault in a copper splice caused an explosion. Since then, Cern has been working to investigate, repair and eliminate the fault, and to get the LHC cooled to operational temperatures.
"The LHC is a far better understood machine than it was a year ago," said Cern’s director for accelerators, Steve Myers, in the statement. "We've learned from our experience, and engineered the technology that allows us to move on."
The aim of the LHC, which has taken 15 years and €10bn to build, is to conduct particle collision experiments that could shed light on fundamental questions about the origins and nature of the universe.