mercredi 1 avril 2015

CERN - LHC restart back on track

CERN - European Organization for Nuclear Research logo.

April 1, 2015

Yesterday, the teams working on the Large Hadron Collider (LHC) resolved the problem that had been delaying the restart of the accelerator. A few days ago, a short circuit to ground occurred in one of the connections between a magnet and its diode. These diodes are part of the protection system for the LHC’s superconducting magnets: they divert the current into a parallel circuit in the event of a quench, i.e. when the magnet changes from a superconducting to a conducting state.

Image above: Various tests were carried out last week to identify the cause of the fault detected between a magnet and its diode. (Image: Maximilien Brice/CERN).

During the training of the magnets for a beam energy of 6.5 TeV, a metal fragment became stuck in the connection, creating a short circuit to ground and preventing the diode from operating correctly. After having located the fault and carried out precise measurements, the accelerator teams decided to melt the metal fragment, in a similar way to blowing a fuse. Yesterday they injected a current of almost 400 amps into the diode circuit for just a few milliseconds, in order to make the fragment disintegrate. And it worked! Measurements made today showed that the short circuit had disappeared.

Now the LHC teams must requalify the sector in which the fault occurred, i.e. carry out current tests on all of the circuits, particularly the dipole magnet circuit which carries currents of up to 11,000 amps. Once these tests have been completed, the teams will begin the last steps for commissioning the whole machine. The largest collider in the world should be ready for beam in a few days’ time. Watch this space!


CERN, the European Organization for Nuclear Research, is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works. At CERN, the world’s largest and most complex scientific instruments are used to study the basic constituents of matter — the fundamental particles. By studying what happens when these particles collide, physicists learn about the laws of Nature.

The instruments used at CERN are particle accelerators and detectors. Accelerators boost beams of particles to high energies before they are made to collide with each other or with stationary targets. Detectors observe and record the results of these collisions.

Founded in 1954, the CERN Laboratory sits astride the Franco–Swiss border near Geneva. It was one of Europe’s first joint ventures and now has 22 Member States.

Related links:

CERN - In pictures: X-rays probe LHC for cause of short circuit:

CERN - LHC injector tests to begin:

For more information about the European Organization for Nuclear Research (CERN), visit:

Image (mentioned), Text, Credits: CERN/Corinne Pralavorio.

Best regards,

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