Abstract-Individually powered superconducting quadrupoles with a coil bore of 70 mm will be installed in the LHC insertions, in areas where increased geometrical acceptance and improved field quality are required. The quadrupoles feature a four-layer coil, designed on the basis of two graded 8.3 mm wide Rutherford-type NbTi cables. The magnets have a magnetic length of 3.4 m and a nominal gradient of 160 T/m at 4.5 K and 3610 A. A total of 26 quadrupoles are in production at ACCEL Instruments (Germany). In this report we present the experience in fabrication of the pre-series magnets and the results of the initial qualification tests.
Abstract-A collaboration agreement between CERN and CEASaclay resulted in the successful development and construction of prototypes of the LHC main superconducting quadrupole magnets and their assembly into cold masses. A call for tender was issued in October 1999 and led to the adjudication of a contract to ACCEL Instruments. A number of components will be provided by CERN to be used either directly by ACCEL for integration into the cold mass units or by subsuppliers before delivery to ACCEL. During the series fabrication, CEA's engineers and technicians, already experienced from their prototype work, will ensure the technology transfer and the technical follow-up in the factory. ACCEL had to adapt two large fabrication halls to the needs of the magnet fabrication and the cold mass assembly. Procedures for a tight quality assurance and the logistics for the timely supply of components and a high production rate are being established in close collaboration by the three parties concerned.
By the end of August 2005 about 320 of the 400 main LHC quadrupole magnets have been fabricated and about 220 of them assembled into their cold masses, together with corrector magnets. About 130 of them have been cold tested in their cryostats and most of the quadrupoles exceeded their nominal excitation, i.e. 12,000 A, after no more than two training quenches. During this series fabrication, the quality of the magnets and cold masses was thoroughly monitored by means of warm magnetic field measurements, of strict geometrical checking, and of various electrical verifications. A number of modifications were introduced in order to improve the magnet fabrication, mainly correction of the coil geometry for achieving the specified field quality and measures for avoiding coil insulation problems. Further changes concern the electrical connectivity and insulation of instrumentation, and of the corrector magnets inside the cold masses. The contact resistances for the bus-bar connections to the quench protection diodes and the elimination of insulation problems of the main bus-bars required special attention. To this must be added actions for solving of interface problems to the neighbouring magnets in the machine and to the cryogenic feed line. ACCEL Instruments established a rigorous quality assurance program used not only for maintaining the quality of their fabrication and their sub-suppliers, but also to inspect the incoming CERN supplies and to avoid integrating faulty components. II. PERFORMANCE OF MAGNETSBefore being assembled into the magnet yoke, each collared coil is submitted to warm magnetic field measurements [5]. These are repeated once the magnet is mounted into its cold mass. From these measurements one can already judge on the field quality at cold, relying on the warm to cold correlation for the different multipole components. The most prominent ones for a quadrupole
By end of November 2006, the last main superconducting quadrupole cold mass needed for the installation was delivered by ACCEL Instruments to CERN. In total, 360 cold masses for the arc regions of the machine and 32 special units dedicated to the dispersion suppressor regions are installed in the LHC ring. The latter ones contain the same main magnet but different types of correctors and are of increased length with respect to the regular arc ones. The end of the fabrication of these magnets coincided with the end of the main dipole deliveries allowing a parallel assembly into their cryostats and installation into the LHC tunnel. The positioning into the tunnel was optimized using the warm field measurements performed in the factory. On the other hand, the correct slot assignment of the quadrupoles was complicated due to the multitude of variants and to the fact that a number of units needed to be replaced by spares which were customized for other slots. The paper gives some final data about the successful fabrication at ACCEL Instruments and explains the issue of their best positions in the machine. AbstractBy end of November 2006, the last main superconducting quadrupole cold mass needed for the installation was delivered by ACCEL Instruments to CERN. In total, 360 cold masses for the arc regions of the machine and 32 special units dedicated to the dispersion suppressor regions are installed in the LHC ring. The latter ones contain the same main magnet but different types of correctors and are of increased length with respect to the regular arc ones. The end of the fabrication of these magnets coincided with the end of the main dipole deliveries allowing a parallel assembly into their cryostats and installation into the LHC tunnel. The positioning into the tunnel was optimized using the warm field measurements performed in the factory. On the other hand, the correct slot assignment of the quadrupoles was complicated due to the multitude of variants and to the fact that a number of units needed to be replaced by spares which were customized for other slots. The paper gives some final data about the successful fabrication at ACCEL Instruments and explains the issue of their best positions in the machine.
After the creation of a new dedicated factory and a period of technology transfer, ACCEL Instruments has constructed and delivered the first LHC main quadrupole magnets to CERN. The design of these magnets had been the subject of a close collaboration between CEA-Saclay and CERN. Thus, CEA ensures also the technology follow-up for the fabrication of 400 quadrupole magnets and their cold masses. The two quadrupoles delivered to CERN were bare magnets, i.e. magnets not integrated into their cold masses. The purpose was to verify their performance before fabricating full cold masses. The two magnets were tested at 1.9 K in a vertical cryostat at CERN. For both magnets the current could be ramped up to well above their nominal level before a quench occurred. The second powering provoked on one of the magnets a quench at the ultimate level of excitation and in the other magnet no quench, even after the ultimate current value had been well exceeded. The field quality measurements, as far as possible in the vertical cryostat, confirmed the multipole content already found during the warm field measurements made in the factory. AbstractAfter the creation of a new dedicated factory and a period of technology transfer, ACCEL Instruments has constructed and delivered the first LHC main quadrupole magnets to CERN. The design of these magnets had been the subject of a close collaboration between CEA-Saclay and CERN. Thus, CEA ensures also the technology follow-up for the fabrication of 400 quadrupole magnets and their cold masses. The two quadrupoles delivered to CERN were bare magnets, i.e. magnets not integrated into their cold masses. The purpose was to verify their performance before fabricating full cold masses. The two magnets were tested at 1.9 K in a vertical cryostat at CERN. For both magnets the current could be ramped up to well above their nominal level before a quench occurred. The second powering provoked on one of the magnets a quench at the ultimate level of excitation and in the other magnet no quench, even after the ultimate current value had been well exceeded. The field quality measurements, as far as possible in the vertical cryostat, confirmed the multipole content already found during the warm field measurements made in the factory.
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