COORDINATION OF THE COMMISSIONING OF THE LHC TECHNICAL SYSTEMS

The Large Hadron Collider operation relies on 1232 superconducting dipoles with a field of 8.33T and 400 superconducting quadrupoles with a strength of 220 T/m powered at 12kA, operating in superfluid He at 1.9K. For dipoles and quadrupoles as well as for many other magnets more than 1700 power converters are necessary to feed the superconducting circuits. A sophisticated magnet protection system is crucial to detect a quench and safely extract the energy stored in the circuits (about 1GJ only in one of the dipole circuits) after a resistive transition. Besides, in such complex architecture, many technical services (e.g. cooling and ventilation, technical network, electrical distribution, GSM network, controls system, etc.) have to be reliably available during commissioning. Consequently, the commissioning of the technical systems and the associated infrastructures has been carefully studied. Procedures, automatic control and analysis tools, repositories for test data, management structures for carrying out and following up the tests have been put in place. This paper briefly describes the management structure and the tools created to ensure safe, smooth and rapid commissioning. LHC: ACCELERATOR SYSTEMS AND INFRASTRUCTURES The Large Hadron Collider (LHC) layout [1] has an eight-fold symmetry with eight arcs, separated by eight straight sections (Fig.1). From the point of view of the commissioning, the LHC can be seen as eight separated machines, which can be commissioned in parallel without any interference with respect to the powering chain, cryogenic and vacuum systems. Figure 1: LHC layout. If we look in detail at the components of an arc, we may recognize elementary blocks, called cells, which are 106.9 m long: 23 regular cells are contained in an arc. Every half cell contains one quadrupole and three dipoles, plus a number of lattice, spool piece and close orbit corrector magnets. The unprecedented energy foreseen for the operation of the LHC lays on the superconducting technology of its components: a bending field of 8.33 T requires dipole magnets working at 1.9 K, to carry the nearly 12 kA current necessary to generate such a field. The complex cryogenic system [2] is capable of feeding superfluid helium to the magnets of an almost 3 km continuous cryostat. Together with the superconducting elements and cryogenic equipment, there are three main systems necessary for the safe and reliable commissioning and operation of the LHC: • The quench protection and energy extraction systems (QPS and EE) [3] protect the superconducting circuits in case of unwanted resistive transition (an energy of about 1 GJ has to be safely and rapidly extracted from the dipoles during a quench [4]); the EE counts 32 systems protecting the 24 13kA circuits and 202 systems protecting an equal number of 600A corrector circuits • The power converters (PC) provide the conversion AC/DC prior to energize the magnets; a PC can be divided in a power part acting as a voltage source and two independent current transducers, plus a digital Function Generator Controller (FGC), which performs the current regulation and makes the link with the control network • The powering interlock controller (PIC) [5] is the backbone of the safety control of the powering chain. A total of 36 controllers are installed and the correct signal exchanges between the linked systems were verified. The ancillary systems completing the picture are: the AC distribution, the cooling and ventilation for the equipment in the tunnel, the DC cable distribution, the Ethernet, Wi-Fi and fieldbus communication networks, the access control system, the radiological monitoring and all the personnel safety systems distributed along the tunnel and service areas All the above mentioned systems have being extensively tested by the equipment owners under the coordination of the Hardware Commissioning team. MOPC118 Proceedings of EPAC08, Genoa, Italy 04 Hadron Accelerators 340 A04 Circular Accelerators THE HARDWARE COMMISSIONING The LHC is the first high energy particle accelerator for which a specific hardware commissioning phase has been defined. The main part of the literature, regarding commissioning of colliders, is focused on the tests and performance of the systems during beam commissioning; there has never been a global approach to the commissioning of the technical systems in terms of information management, database design and activity coordination (e.g. detailed schedule, planning, resources study, quality assurance, project control, etc.). The closest antecedents of the LHC are the String I and String II projects: a LHC prototype half-cell and a full arc cell respectively, which were installed, commissioned and operated at CERN between 1994 and 2003. These yielded precious information on the collective behaviour of the technical systems during operation, as well as the first estimations of time and resources required for the machine commissioning.