Engineers Aline Piguiet and Markus Albert take x-ray images to pinpoint the cause of a short circuit in the Large Hadron Collider.

Engineers Aline Piguiet and Markus Albert take x-ray images to pinpoint the cause of a short circuit in the Large Hadron Collider.

Maximilien Brice/CERN

Short circuit in Large Hadron Collider is fixed

Efforts to fix a short circuit in the world's largest atom smasher, the Large Hadron Collider (LHC), have been successful, according to officials at the European particle physics lab, CERN, near Geneva, Switzerland.

Engineers detected the short on 21 March as they prepared to restart the LHC—the 27-kilometer-long collider that in 2012 discovered the Higgs boson—after 2 years of repairs. That short was apparently caused by a wayward bit of metal inside the "diode box" in one of the superconducting dipole magnets that steer particles as they hurtle around the LHC. Now, engineers have succeeded in burning off the piece of metal by injecting 400 amps of current into the shorted circuit, to blow it a bit like you'd blow a fuse.

"The progress is good. … The short has disappeared. We are back into what we would call more routine test phase now," says Paul Collier, head of the beams department at CERN.

If all goes well, the LHC could be ready to run by this weekend. Before that can happen, engineers will need to retest the entire 6-kilometer circuit that powers the dipole magnets in the sector in which the short appeared—a process that will require at least a few days. Researchers will then need a few more days to prepare the whole machine for the beam. Before the short appeared, CERN officials had hoped to start circulating particles last week.

The fix avoids a considerably longer shutdown. If initial attempts to obliterate the piece of metal had failed, engineers might have had to open up the machine to remove it, a step that could have added weeks or months to the schedule.

"It's a matter of days, now, before first beam, certainly not weeks," Collier says. "Fingers crossed that nothing else goes wrong, of course."