Full steam ahead!

Following the completion of the campaign to improve the reliability of the cabling for the new Quench Protection System, the main dipoles and quadrupoles of the eight LHC sectors have now been commissioned up to a current of 6 kAmps. In the early hours of Sunday 28 February, the beams were circulating again in the LHC: the longest run in CERN's history has just started!


One of the first beam shots in the LHC on Sunday 28th February early morning.

During the campaign that the LHC teams carried out over the last few weeks to ensure the correct functioning of the LHC magnets at high current, the several thousand channels of the new Quench Protection System were verified and the resistance of the 10,000 splices connecting the magnets was precisely measured, showing no unacceptably anomalous values.

In order to operate the LHC without risk to the magnet system, it must be possible to switch off the magnets and extract the stored energy in about ten seconds at all times. At the same time, efforts have been concentrated on correctly tuning the parameters of the Quench Protection System in order to avoid it triggering the beam dump when not technically necessary.

Having completed the magnet-powering tests at 6 kAmps, the hardware commissioning team has handed the machine over to the operation team. The initial operations have included tests without beams to verify the correct functioning of all the systems (magnets, radiofrequency, collimators, injection and beam abort systems, etc.) in unison.

By midnight on Saturday 27 February the machine was ready to receive the beams, and injection started. By early the next morning both beams were circulating again in the LHC (see figure). Sunday was then dedicated to the optimization of the beam trajectory and of the other optical parameters, as well as to the control of the beams by the radio-frequency cavities that keep the protons bunched.

In the CERN Control Centre, the operators are now working on optimising the beam parameters and improving the beam lifetime. The energy of the proton beams is currently 450 GeV. The first energy ramp-up is expected in the next few days. High-energy collisions are planned for the end of March.

by CERN Bulletin