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EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCHCERN - ACCELERATORS AND TECHNOLOGY SECTOR

The First Long Shutdown (LS1) for the LHC

F. Bordry, S. Baird, K. Foraz, A.-L. Perrot, R. Saban, J.Ph. TockCERN, Geneva, Switzerland

The LHC has been delivering data to the physics experiments since the first collisions in 2009. The first long

shutdown (LS1), which started on 14 February 2013, was triggered by the need to consolidate the magnet

interconnections to allow the LHC to operate at the design energy of 14 TeV in the centre-of-mass. It has now become

a major shutdown, which, in addition, includes other repairs, consolidation, upgrades and cabling across the whole

accelerator complex and the associated experimental facilities. A detailed CERN-wide resource-loaded schedule was

prepared aiming at resuming LHC physics in early 2015, while the rest of the CERN complex will gradually start up

again in the second half of 2014.

The paper describes the preparation phase with the prioritisation of the activities, the building of the teams and the

planning of the shutdown. Then, it gives an overview of the injector activities and the main projects in the LHC. The

decision to restart at 6.5 TeV after the LS1 is recalled.

Presented at IPAC'2013, 4th International Particle Accelerator Conference12-17 May 2013 - Shanghai, China

Geneva, Switzerland

CERN-ATS-2013-0084

July 2013

THE FIRST LONG SHUTDOWN (LS1) FOR THE LHC

F. Bordry, S. Baird, K. Foraz, A.L. Perrot, R. Saban, J.P Tock, CERN, Geneva, Switzerland

Abstract The LHC has been delivering data to the physics

experiments since the first collisions in 2009. The first long shutdown (LS1), which started on 14 February 2013, was triggered by the need to consolidate the magnet interconnections to allow the LHC to operate at the design energy of 14 TeV in the centre-of-mass. It has now become a major shutdown, which, in addition, includes other repairs, consolidation, upgrades and cabling across the whole accelerator complex and the associated experimental facilities. A detailed CERN-wide resource-loaded schedule was prepared aiming at resuming LHC physics in early 2015, while the rest of the CERN complex will gradually start up again in the second half of 2014.

The paper describes the preparation phase with the prioritisation of the activities, the building of the teams and the planning of the shutdown. Then, it gives an overview of the injector activities and the main projects in the LHC. The decision to restart at 6.5 TeV after the LS1 is recalled.

INTRODUCTION Following the incident in one of the main dipole

circuits of the LHC on September 19th 2008, a detailed analysis was carried out [1]. Thanks to the availability of spare magnets, Sector 3-4 could be repaired in 6 months. In addition, a global consolidation of the magnet protection system and important re-engineering of several systems took place so that such an incident would be avoided in the future.

An upgraded quench protection system was designed and installed to protect all bus-bar joints of the arc main dipole and main quadrupole circuits [2]. In parallel an improved pressure relief system for the insulation vacuum was installed on the magnet cryostats. But in order to restart quickly the LHC (November 2009) and to provide data to the experiments, it was decided to warm-up only four LHC sectors, therefore the 200 mm diameter valves for the improvement of the pressure relief system were only installed on these four sectors.

The interconnections between the LHC main magnets are made of soldered joints (splices) of two superconducting cables stabilized by a copper bus bar. The measurements performed in 2009 in the four warm sectors demonstrated that there are defective copper bus bar joints in the machine (10-15% of the high current interconnections). Based on these measurements, it was decided to restart the LHC operation at 3.5 TeV and to consolidate the LHC during the LS1 in 2012. With the respectable integrated luminosity in 2011, the CERN management decide to run the LHC through 2012 to give

to the experiments the data needed to fully explore this energy range before moving up to higher energy. To enhance the discovery potential, after two years of operation and an operational experience with stored beams exceeding 100 MJ, the beam energy was increased to 4 TeV in 2012.

Thanks to the fantastic LHC performance [3], this staged strategy proved successful and culminated, with the announcement of the discovery of a Higgs-like boson on 4th July 2012.

LS1 STRATEGY AND RESSOURCES As described above, the LS1 was triggered by the need

to consolidate the magnet interconnections to allow the LHC to operate at the design energy of 14 TeV in the centre-of-mass. It became rapidly a major shutdown, which, in addition, includes other repairs, consolidations, upgrades and cabling across the whole accelerator complex and the associated experimental facilities. LS1 will see a massive programme of maintenance for the LHC and its injectors in the wake of more than three years of operation without the long winter shutdowns that were the norm in the past.

The LS1 preparation started just after the decision to resume the LHC operation at 3.5 TeV, i.e. more than three years ago. The strategy was to define the duration of key activities needed for safe and reliable operation of the CERN accelerator complex (LHC and its injectors) to run the LHC at 7 TeV at the nominal luminosity. After several iterations with the technical coordination of the LHC experiments, the LHC machine and its injectors, the minimum time needed from “beam off” to “beam on” in the LHC was determined to be 20 months. Rapidly it became clear that it would be necessary to prioritize all the activities requested by equipment groups and the projects; this to ensure that the 20 month time frame would be sufficient to perform all the consolidation and upgrades needed to achieve the goals of LS1 (as well as carry out the full maintenance of the different systems),. Often these interventions are planned and organized in terms of the resources in the groups, therefore it was vital to gather all the information on the support needed from other groups, to check the coactivity conflicts and to define the required manpower. Regular and dedicated meetings were held with the different stakeholders to obtain a clear and complete picture of the activities related to the accelerator complex and the LHC experiments. All the information was compiled in a database and a special software tool (PLAN) was developed as a decision support tool.

The five following levels were set to prioritize all the activities:

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Proceedings of IPAC2013, Shanghai, China MOZB202

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MOZB202 Proceedings of IPAC2013, Shanghai, China

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