LHC Report: Even accelerators need a break

The LHC technical stop is in full swing, with a lot of essential maintenance work on the accelerator services, such as electricity distribution, cooling, ventilation, cryogenic systems, access and safety systems, vacuum, cranes and lifts, being crammed into the few weeks before the start of the 2011 run in February.


Team changing a magnet in the SPS accelerator. 

In addition to the maintenance work a number of modifications are being made to the accelerator for 2011. These include the installation of small solenoids to combat the build-up of electrons inside the vacuum chamber with the increasing proton beam intensity; the replacement of a number of UPS (Uninterruptible Power Supply) installations, which are vital to ensuring the continuity of the electrical supply to essential systems such as the cryogenics; the installation of additional capacitors on the QPS (Quench Protection system) to prepare for a possible increase in beam energy in 2011; the completion of the programme to replace all electrical transformers containing traces of PCBs (polychlorinated biphenyls); plus a host of other improvements to RF, beam instrumentation, power convertors, kickers, etc., which are all part of the life of a CERN accelerator. The work is proceeding as planned and the preparations for refilling the machine with liquid helium are already getting under way this week.

The technical stop does not just concern the LHC: during the same period a similar maintenance programme is under way in the injector chain, namely at LINAC2, PSB, PS and SPS. An example of this work is the programme to exchange 8 magnets in the SPS machine. This is part of a regular preventive maintenance programme in which the SPS magnets are exhaustively tested by teams from TE/MSC at the end of each year and those presenting any initial signs of weakness are changed during the accelerator stop. This is a complicated task as it requires the cooperation of more than 6 different groups and teams all working together to very tight deadlines. At the PS, the present technical stop is also being used to begin the commissioning of the new PS main power supply (POPS). This commissioning will begin at the end of January. In 2011, POPS will replace the old SIEMENS rotating machine, which has powered the PS magnets since 1968. These are two examples of the extensive work required to ensure that the LHC injectors remain fully operational for many years to come.

All planned activities are on schedule for LHC hardware testing to begin on 24 January, starting with the Electrical Quality Assurance (ELQA) testing of the electrical circuits. The technical stop will finish at the end of January, and beam operation will start again in mid-February after a two-week hardware-commissioning period.

by CERN Bulletin