The world's largest superconducting solenoid magnet, part of the experiment in smashing atoms, September 10. The world's largest particle collider has been stopped, a week after its startup, as a result of an electrical fault, the European Organisation for Nuclear Research (CERN) said.
The problem affected a cooling system for high-powered magnets designed to steer beams of particles around the Large Hadron Collider's 27-kilometre (16.9-mile) circular tunnel, CERN said.
The LHC "is still in commissioning phase, it's a very complex tool and it's normal for there to be stoppages," a CERN spokeswoman told AFP.
Commissioning work stopped on Wednesday, but was likely to resume later Thursday, she said.
The LHC took nearly 20 years to complete and at six billion Swiss francs (3.76 billion euros, 5.46 billion dollars) is one of the costliest and most complex scientific experiments ever attempted.
It aims to resolve some of the greatest questions surrounding fundamental matter, such as how particles acquire mass and how they were forged in the "Big Bang" that created the Universe some 13.7 billion years ago.
Counter-rotating beams, comprising strings of protons, are whizzed around the tunnel and then are smashed together in four huge laboratories.
Arrays of detectors swathing the walls of these chambers will trace the sub-atomic rubble spewed out from the collision, looking for signatures of novel particles.
The September 10 switch-on saw the testing of a clockwise beam, and then an anticlockwise beam. The first collisions are not expected for a number of weeks, given the long process of testing the LHC's equipment.
The steering magnets in the LHC tunnel are chilled to as low as -271 degrees Celsius (-456.25 degrees Fahrenheit), which is close to absolute zero and colder than deep outer space.
At this extreme temperature, electrical currents overcome resistance, thus making it easier and cheaper to power electro-magnets.