On Monday, teams working on the Large Hadron Collider resolved a problem that had been delaying the restart of the accelerator, according to a statement from CERN.
On March 24, the European physics laboratory announced that a short circuit to ground had occurred in one of the connections with an LHC magnet. LHC magnets are superconducting, which means that they can maintain a high electrical current with zero electrical resistance. To be superconducting, the LHC magnets must be chilled to almost minus 460 degrees Fahrenheit.
The short circuit occurred between a superconducting magnet and its diode. Diodes help protect the LHC’s magnets by diverting electrical current into a parallel circuit if the magnets lose their superconductivity.
When teams discovered the problem, all eight sections of the LHC were already cooled to operating temperature. To fix the problem, they knew that they might have to go through a weeks-long process of carefully rewarming and then recooling one section.
The short circuit was caused by a fragment of metal caught between the magnet and the diode. After locating the fragment and examining it via X-ray, engineers and technicians decided to try to melt it. They could do this in a way similar to blowing a fuse. Importantly, the technique would not require them to warm up the magnets.
They injected almost 400 amps of current into the diode circuit for a few milliseconds. Measurements made today showed the short circuit had disappeared.
Now the teams must conduct further tweaks and tests and restart the final commissioning of the accelerator. The LHC could see beams as early as next week.