Large Hadron Collider back on track as short circuit fixed

Engineers working on the world’s largest atom smasher, CERN's Large Hadron Collider, have managed to fix a short circuit that prevented them going ahead with the planned restart of the accelerator.

On March 21 engineers working at CERN, the European particle physics lab near Geneva, flagged a fault in the Large Hadron Collider (LHC), but restart plans resumed earlier this week. The first beams could now be circulating in the machine sometime between Saturday and Monday.

“We are confident of being able to restart the machine over the weekend, as all of the tests performed so far have been successful,” Frédérick Bordry, director for accelerators and technology at CERN, said in a statement.

The short circuit, which occurred in one of the connections between a magnet and its diode, turned out to be caused by a small piece of metal that became stuck and stopped the diode from operating correctly, CERN explained.

The LHC team successfully managed to melt the metal fragment in a similar way to blowing a fuse by injecting a current of almost 400 amps into the diode circuit for a few milliseconds. However, before the restart can happen engineers must carry out tests on all of the circuits - the dipole magnet circuit in particular - and will then prepare the whole machine for the beam injection.

“The progress is good. The short had disappeared,” Dr Paul Collier, head of CERN’s beams division, told Science. “We are back into what we would call more routine test phase now. It’s a matter of days, now, before first beam, certainly not weeks… Fingers crossed that nothing else goes wrong, of course.”

The diodes are part of the protection system in place for the collider’s magnets, diverting the current into a parallel circuit if the magnet suddenly changes from a superconducting state to a conducting one.

The problem was resolved fairly quickly, as it didn’t involve direct access to the diode box. Otherwise, the warm-up, intervention and subsequent cool-down would have taken around six weeks, CERN said.

The machine, with a $5bn price tag, earned its place in the history books in 2012 for discovering the Higgs boson. It was the missing particle in the Standard Model that explains our physical world and crucially is believed to be responsible for giving mass to all other particles.

Read more:
CERN's Large Hadron Collider: restarting the Big Bang Machine

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