| Paper | Title | Page |
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| MOPC103 | Short Circuit Tests: First Step of LHC Hardware Commissioning Completion | 304 |
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| 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. Between October 2005 and September 2007 the so-called short circuit tests were carried-out in the 15 underground areas where the power converters of the superconducting circuits are located. The tests were aimed at the qualification of the normal conducting components of the circuits: the power converters, the normal conducting DC cables between the power converters and the LHC cryostat, the interlocks and energy extraction systems. In addition, the correct functioning of the infrastructure systems (AC distribution, water and air cooling, control system) were validated. The final validation test for each underground area was the powering of all converters at ultimate current during 24h. This approach highlighted a few problems that were solved long before the beginning of magnet commissioning and beam operation. | ||
| MOPC118 | Coordination of the Commissioning of the LHC Technical Systems | 340 |
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| 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. | ||
| WEPP010 | Scheduling the Powering Tests | 2545 |
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| The Large Hadron Collider is now entering in its final phase before receiving beam, and the activities at CERN between 2007 and 2008 have shifted from installation work to the commissioning of the technical systems (“hardware commissioning”). Due to the unprecedented complexity of this machine, all the systems are or will be tested as far as possible before the cool-down starts. Systems are firstly tested individually before being globally tested together. The architecture of LHC, which is partitioned into eight cryogenically and electrically independent sectors, allows the commissioning on a sector by sector basis. When a sector reaches nominal cryogenic conditions, commissioning of the magnet powering system to nominal current for all magnets can be performed. This paper briefly describes the different activities to be performed during the powering tests of the superconducting magnet system and presents the scheduling issues raised by co-activities as well as the management of resources. | ||
| WEPP073 | Simulation Studies of Impact of SPS Beam with Collimator Materials | 2689 |
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Over the past years detailed simulations were carried out to study the impact of the full LHC 7 TeV beam on a target to assess the damage caused to the equipment as a result of an accident, especially to collimators and beam absorbers, and to estimate the thickness of a sacrificial absorber that would be required to stop the beam. This study has shown that the target material will be strongly heated by the beam and transformed into plasma. It has been estimated that the beam would tunnel up to 30 m in solid copper and to about 10 m in solid carbon*. Another interesting outcome of this study was that the LHC beam could be used as a tool to study High-Energy-Density (HED) states in matter. Using the same tools, we recently studied the impact of the SPS 450 GeV proton beam on tungsten and copper targets**. It has been found that the material will be seriously damaged and some tunneling of the beam into the target is expected. It should be possible to validate the predictions with a test facility to deflect the high energy high intensity SPS beam on collimator and absorber materials that will become operational in the next years.
*N. A. Tahir et al. J. Appl. Phys. 97 (2005) 083532. |
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| WEPD028 | Performance of the Superconducting Corrector Magnet Circuits during the Commissioning of the LHC | 2470 |
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| The LHC is a complex machine requiring more than 7400 superconducting corrector magnets distributed along a circumference of 26.7 km. These magnets are powered in 1380 different electrical circuits with currents ranging from 60 A up to 600 A. Among the corrector circuits the 600 A corrector magnets form the most diverse and differentiated magnet circuits. About 60000 high current connections had to be made. A minor fault in a circuit or one of the superconducting connections would have severe consequences for the accelerator operation. All magnets are wound from various types of Nb-Ti superconducting strands, and many contain resistors to by-pass the current in case of the transition to the normal conducting state in case of a quench, and hence reduce the hot spot temperature. In this paper the performance of these magnet circuits is presented, focussing on the quench current and quench behaviour of the magnets. Quench detection and the performance of the electrical interconnects will be dealt with. The results as measured on the entire circuits will be compared to the test results obtained during the reception tests of the individual magnets. | ||
| WEPD029 | Performance of the Main Dipole Magnet Circuits of the LHC during Commissioning | 2473 |
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| During hardware commissioning of the Large Hadron Collider, 8 main dipole circuits and 16 main quadrupole circuits are tested at 1.9 K and up to their nominal current. Each dipole circuit contains 154 magnets of 15 m length, and has a total stored energy of up to 1.1 GJ. Each quadrupole circuit contains 47 or 51 magnets of 5.4 m length, and has a total stored energy of up to 20 MJ. All magnets are wound from Nb-Ti superconducting Rutherford cables, and contain heaters to quickly force the transition to the normal conducting state in case of a quench, and hence reduce the hot spot temperature. In this paper the performance of these circuits is presented, focusing on the quench current and quench behaviour of the magnets. Quench detection, heater performance, operation of the cold bypass diodes, cryogenic recovery time, electrical joints, and possible magnet-to-magnet quench propagation will be dealt with. The results as measured on the entire circuits will be compared to the test results obtained during the reception tests of the individual magnets. | ||
| THPC145 | Reliability Analysis of the LHC Machine Protection System: Terminology and Methodology | 3327 |
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| The trade-off between LHC machine safety and beam availability is one of the main issues related to the LHC MPS. Several studies have addressed it for different subsystems. They are followed by a project aiming at the development of a methodology which combines agent-based modeling and fault-tree analysis thus allowing a global analysis of the entire MPS. During this project, the need for a clarification and specification of the terminology has become apparent. Besides involving basic terms like safety, reliability and availability, the analysis must take into account the implementation of common design principles such as redundancy, fault tolerance, 'fail-safe' and self-monitoring. These terms and in particular their interrelations easily cause confusion. Since the traceability of the analysis depends on a consistent understanding of the underlying terminology, a terminology frame is being compiled. The paper specifies the most relevant terms and their interrelations. General standard definitions are taken as basis for a specification related to the MPS and its analysis respectively. The developed analysis methodology building on this terminology frame is introduced. | ||
| THPC151 | The Post-Mortem Analysis Software Used for the Electrical Circuit Commissioning of the LHC | 3345 |
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| The hardware commissioning of the LHC has started in the first quarter of 2007, with the sector 7-8. A suite of software tools has been developed to help the experts with the access, visualization and analysis of the result of the tests. Using the experience obtained during this phase and the needs to improve the parallelism and the automation of the electrical circuits commissioning, a new user interface has been defined to have an overview of all pending tests and centralise the access to the different analysis tools. This new structure has been intensely used on sector 4-5 and during this time the test procedures for different types of electrical circuits have been verified, which has also allowed the implementation of new rules and features in the associated software. The hardware commissioning of the electrical circuits enters in a more critical phase in 2008, were the number of the tests executed increases rapidly as test will be performed in parallel on different sectors. This paper presents an overview on the post mortem analysis software, from its beginning as a simple graphical interface to the actual suite of integrated analysis tools. |