Tonight the Large Hadron Collider (LHC) operations team can go home happy in the knowledge that they completed both their “principal” and “personal” goals.

The principal goal — the one for the benefit of the world’s media — was completed at 10:24 am CET (9:24 am BST) by sending a proton beam clockwise all the way around the LHC’s 27 km-long ring. But later today, at 3:02 pm CET, the team’s secret hope came true as it successfully repeated the exercise for the anticlockwise direction.

The time taken to complete both these feats — just under an hour for the first, and precisely an hour for the second — has come to be known as the two “golden hours”.

In an interview with physicsworld.com after the day’s events, Robert Aymar, director general of CERN, the European lab hosting the LHC, maintained he was confident all along that the team would achieve beam circulations in both directions. “We were prepared, and anything could happen,” he said. “But there was always a risk.”

“It is proof that we are now ready for new physics,” he added.

‘We’ve learned a lot’

Although today went more smoothly than anyone had hoped, there were some minor problems. In the control room at 4 am this morning a yellow signal lit up on the monitors, indicating that one of the sectors had heated up slightly as the result of a cryogenics failure. An hour later engineers were busy at work on the faulty compressor that caused it, and within a few hours it was fixed.

However, cryogenics briefly returned to haunt the operations team at lunchtime. Steve Myers, the head of the accelerators department, said that his team is planning look into the cause of that occurrence. “[Cryogenic issues are] to be expected because this is an enormous system and it still has its teething problems,” he explained. “But we’ve learned a lot about the system today and I’m sure that from today onwards we’ll be learning even faster.”

During a press conference, director generals of CERN, both past and present, lauded the LHC for the strength of its international collaboration and the new physics it is expected to bring.

Chris Llewellyn Smith, who was director general between 1994 and 1998 and who took the case for a proton–proton collider to the CERN council in the late 1970s, called it a “fantastic day”. “We are now continuing a quest that is as old as civilization,” he added. “And if you were being pompous, you would say that that quest was the definition of civilization.”

Herwig Schopper, who was director general between 1981 and 1988, compared today’s LHC “switch on” with the event for CERN’s previous flagship accelerator, the Large Electron-Positron collider (LEP), in 1989. “I remember 19 years ago in the LEP control room it took 12 hours,” he said. “Today it took one — and this is based on the competence of the CERN engineers. Without this competence, CERN would not be where it is today.”