Towards the end of the technical stop

After several weeks of hard work, the short technical stop of the LHC accelerator is coming to an end. Following a very intense campaign to repair and retest many thousand high voltage connectors, the upgraded magnet protection system is being commissioned. During this period, the current in the main dipole and quadrupole magnets is carefully increased up to 6kA, required to collide protons at 7TeV centre-of-mass energy. This has been achieved for most of the sectors.

The parameters of the upgraded magnet protection system are accurately calibrated. This operation is needed in order for the magnet protection system to be triggered only when a real problem occurs. The system is now able to detect a transition from superconducting to normal conducting state of the superconducting cable joints between magnets, a necessary condition to operate the magnet system above 2kA. Highly accurate measurements of the joint resistances have been performed by stepping up the current to 5kA.

The magnets and the protection system have responded well to the tests done so far, making it possible for the teams to plan for beam operation in the next week. As the last step, the magnets in all sectors will be powered together for several hours. Beam injection in the LHC will take place soon after these tests are finished.

by CERN Bulletin