The world's most expensive experiment, which aims to unlock the secrets of the Big Bang, has been stopped for two months for repair work.
The cooling system for the Large Hadron Collider's high-powered magnets that steer beams of particles around the tunnel malfunctioned earlier this week.
The European Organisation for Nuclear Research (Cern) replaced the equipment in the underground tunnel near Geneva, Switzerland, but the damage is worse than previously thought.
Cern spokesman James Gillies said: "There has been an incident in a test. One section of the machine will have to be repaired.
"In layman's terms, the LHC is a great big fridge, and part of the power supply failed."
The faulty electrical connection between the two magnets led to a ton of liquid helium being leaked into the tunnel.
The magnets are chilled to as low as -271 degrees Celsius, which is close to absolute zero and colder than deep outer space.
Mr Gillies said the damaged section will have to be warmed up well above absolute zero so that repairs can be made.
He expects the atom smasher to remain switched off for at least two months.
The LHC, which started on September 10, took nearly 20 years to complete and at ?4.4bn 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 scientists believe created the universe 17 billion years ago.
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