The stored energy and intensity of the LHC beam exceed the damage level of the machine and the quench level of the magnets by far. Therefore a robust and reliable collimation system is required which prevents the quenching of the magnets during regular operation and protects the accelerator components from damage in the event of beam loss. To assure that the installed collimators will protect the machine and permit the required performance of the collider, an appropriate hardware commissioning has to be implemented. In this contribution we describe the procedures for the hardware commissioning of the LHC collimation system. These procedures will establish the required precision and reliability of collimator movements and settings before the start of beam operation. Large Hadron Collider Project AbstractThe stored energy and intensity of the LHC beam exceed the damage level of the machine and the quench level of the magnets by far. Therefore a robust and reliable collimation system is required which prevents the quenching of the magnets during regular operation and protects the accelerator components from damage in the event of beam loss. To assure that the installed collimators will protect the machine and permit the required performance of the collider, an appropriate hardware commissioning has to be implemented. In this contribution we describe the procedures for the hardware commissioning of the LHC collimation system. These procedures will establish the required precision and reliability of collimator movements and settings before the start of beam operation.

The LHC dipoles magnets are produced in 5 industrial production sites in Europe. The production is well underway and more than half of the total quantity has been delivered to CERN. One of the important characteristics of the dipole magnets is their geometry. To achieve the requested mechanical tolerances on the magnets, which are 15 m long and have a 28 t mass, the final assembly operations includes precise optical measurements. To ensure the good quality and high production rate, the final assembly procedure has been automated as much as possible. The authors report here about the assembly procedure, the features of the software that guides the optical measurements (and consequently the assembly operations) and the results obtained on the geometry in the different sites. Abstract-The LHC dipoles magnets are produced in 5 industrial production sites in Europe. The production is well underway and more than half of the total quantity has been delivered to CERN. One of the important characteristics of the dipole magnets is their geometry. To achieve the requested mechanical tolerances on the magnets, which are 15 m long and have a ≈28 t mass, the final assembly operations includes precise optical measurements. To ensure the good quality and high production rate, the final assembly procedure has been automated as much as possible. The authors report here about the assembly procedure, the features of the software that guides the optical measurements (and consequently the assembly operations) and the results obtained on the geometry in the different sites.

Abstract-In order to provide the necessary mechanical aperture for the LHC beam, the main dipole cold masses have to match precisely the nominal circular trajectory of the particles beam. The requirements on the dipole cold mass geometry are dictated by the LHC beam optics and by the allowed limits of mechanical deformation of the interconnection bellows. Keeping the tight tolerances that are imposed necessitates a well controlled bending process and the use of a high accuracy 3D measuring instrument for checking the geometry of the cold mass throughout many manufacturing stages up to the final inspection.The dipole cold mass pre-series production started in 2000. It is almost completed at the three sites. In this paper, we report on the problems encountered to shape correctly the cold masses, their effect on interconnection of the dipole cold masses and on the mechanical aperture. On one side measures to improve the production process in terms of accuracy and reproducibility were taken, on the other side the assembly tolerances could be relaxed following a thorough review of the machine requirements.The summary of the encountered problems, corrective actions and results obtained on the pre-series cold masses are presented and discussed.

Abstract-In order to predict the mechanical behavior of the LHC dipole cold mass in situations such as handling, transport and cool down, a number of important structural parameters are required. The dipole's flexural rigidity determines entirely the mechanical elastic behavior of the cold mass. Therefore, models of a bent cold mass were created to calculate its rigidity. This paper presents a simplified parametric finite element model, created to study the deflection of the cold mass in different situations and supporting conditions. The sensitivity of the models to the supporting conditions is computed. To provide the finite element and the analytical models with input, the deflection of the cold mass under discrete loads in normal condition and then 90-degrees rotated were measured with a laser tracker. By comparing models with measurements, the vertical and transversal rigidity of the cold mass assembly are determined. Additionally, the paper reports on the plastic behavior of the cold mass assembly in the range of the deformations that are needed to correct cold masses that result, after final welding of the outer skin, with unacceptable sagitta.