LS1 Report: achieving the unachievable

The dismantling and extraction of a defective DFBA module from LHC Point 6, announced a few weeks ago, has been completed without a hitch. The DFBAs in the LHC are unique and irreplaceable components that must be handled with care.


The Transport team extract the defective module in one of the two DFBAs at Point 6. This module was brought to the surface, where it is currently being repared.

Dismantling and extracting part of an electrical feed box (DFBA) had not been planned and could not have been foreseen. Nonetheless, that is what had to be done. When the LS1 teams discovered that the bellows of one of the DFBAs in Sector 5-6 were damaged - and completely inaccessible - they were not exactly overwhelmed with solutions. In fact, they had only one option: to dismantle them and take them up to the surface.

Step 1: measure the alignment of the module to be taken out in relation to the beam lines to ensure that when the DFBA is put back in, it is in the right position for the beam to pass through. For that, a precise survey was carried out by CERN’s surveyors. Next, the superconducting cables and cryogenic pipes were disconnected by a team of experts from the TE-MSC Group.

Finally, it was time for the dismantling. The module in question, which weighs almost two tonnes, is a particularly tricky part. “This part of the DFBA, known as a 'shuffling module’, was not, in principle, designed to be removable from the rest of the electrical feed box,” explains Antonio Perin (TE-CRG), project leader for the consolidation of the DFBAs during LS1. So the dismantling, coordinated by Didier Lombard (EN-MME), was a delicate job to say the least. So much so that the superconducting cables that pass through the module could not simply be cut, but rather had to be fully disconnected, two metres further along, by a team of experts from the TE-MSC Group. The cables therefore had to be extracted from the module before it could be moved.

“Given the complexity of the operation and the fact that it had never been done before, we enlisted the help of numerous highly qualified people from various CERN departments (EN, TE, BE), possessing expertise in various fields (such as transport),” underlines Said Aiteh (EN-MME), coordinator of LS1 welding work. Together, this team ensured that the dismantling and extraction was a success.” The module is now in Building 112, where the EN-MME team is repairing it. It is scheduled to be reinstalled in its original position in early 2014; an operation that promises to be equally delicate.

Three other defective DFBAs have been identified in the LHC, of which one has already been repaired in situ and a second one is due to be repaired in situ shortly. The third, however, poses more of a problem. In all likelihood, it too will have to be brought to the surface like the Point 6 DFBA. Watch this space.

Meanwhile, elsewhere...

At the PS Booster, the reinstallation of the beam dump is on-going. The decision has also been taken to replace one of the injector’s overhead travelling cranes, and two more will be consolidated. In addition, cable channels have been drilled in preparation for LS2.

The SPS transfer tunnel, TT10, reinforced with steal beams.

At the PS, five of the seven main magnets are already in the magnet workshop. A team of specialists arrived from Russia last week to work on their consolidation.

At the SPS, steel reinforcement beams have been fixed to the roof of one of the transfer tunnels (TT10) to address the structural weaknesses observed there.

At the LHC, the first car of the SMACC train has reached Sector 3-4, the penultimate sector needing to be consolidated. 


by Anaïs Schaeffer