Hygromechanical behaviour of CFRP under cyclic humidity loadings

Stable lightweight structures are key issues in the design and construction of the LHC high precision particle detectors. This paper presents the results of long term measurements performed on plates manufactured in Carbon Fibre Reinforced Plastics (CFRP), material selected for these structures, subjected to cyclic humidity loadings. Test procedures are detailed; results on moisture absorption are described together with the related displacement measurements. These results indicate that cycling composites in the operating conditions of the LHC trackers does not provoke any major internal damage

Design rules for vacuum chambers

Producing a vacuum chamber means defining the boundary conditions (inner and outer envelopes, operational constraints, etc.), choosing the material, designing the parts, manufacturing and assembling these parts together and putting them under vacuum. This paper gives the methodology, methods and hints for designing vacuum chambers

Mechanical Behaviour of the LHC Cryodipoles

The LHC cryodipoles are slender and heavy objects more than 15-m long. The major components of the cryodipole assembly are the 28-tonne cold mass, supported on its three Glass-Fibre-Reinforced-Epoxy support posts and the 4-tonne vacuum vessel. The performance of the LHC depends very much upon the accurate positioning of the dipoles and the beam tubes, in particular to maximise the useful beam apertures. The cryodipoles will be conditioned and measured in surface assembly buildings, then handled and transported to their positions in the tunnel and, finally, aligned. This paper presents the static and dynamic studies of the cryodipole in different configurations. The tests and analyses carried out have led to a thorough understanding of the mechanical behaviour of the cryodipoles. From the static analysis, an hyperstatic supporting system is proposed in order to minimise the systematic deflections and the effects due to changing temperature conditions in the tunnel. The dynamic analysis has shown that the cryodipole resonates at a series of very low natural frequencies and, moreover, shows a low damping value. Since the dynamic loads during transport and handling are in the low frequency range, the cryodipole components are potentially susceptible to damage. Simulations have included the truck suspension for road transport and the lifting device for handling with a crane. Solutions coping with the transport and handling conditions are presented

Implementing an engineering data management system for the LHC accelerator and experiments: the CEDAR project

The huge quantities of data required for the design, building and operation of the LHC and its experiments require consistent management and storage. The CEDAR project aims at implementing an Engineering Data Management System (EDMS) at CERN. After having defined what is an EDMS and what are the expected benefits for the LHC we present the activities held in CEDAR, during the selection and pilot project phases. Lessons learned and conclusions reached through the pilot projects are then summarised

The Electrical Distribution Feed Box for the LHC Prototype Cell

The Electrical Distribution Feed Box (DFB) for the Large Hadron Collider (LHC) Prototype Cell (String 2) is a 6 meter-long 4.6 K / 0.135 MPa liquid helium cryostat which supports and cools 13 kA and 600 A High-Temperature Superconductor (HTS) current leads. These are used for powering the String 2 main dipole and quadrupole superconducting magnets, together with their correctors. The DFB also incorporates the l-plate between its saturated liquid helium bath and the magnet pressurized superfluid helium bath at 1.9 K/ 0.13 MPa. The DFB is built within the frame of a collaboration between CERN and the Budker Institute of Nuclear Physics (Novosibirsk, Russian Federation). It is a complex cryostat satisfying a number of constraints (space available, accessibility, integration) and combining different technologies such as mechanical and electrical engineering, superconductivity, cryogenics and vacuum. The current status of the design and construction of the DFB for the LHC Prototype Cell, together with an outlook towards the LHC arc DFB's, is given

Thermal Conductivity of Structural Glass/Fibre Epoxy Composite as a Function of Fibre Orientation

The LHC, the new superconducting particle accelerator presently under construction at CERN, makes use of some 1200 dipole magnets for orbit bending and 500 quadrupole magnets for focusing/defocusing of the circulating high-energy proton beams. Two or three column-type support posts sustain each cryomagnet. The choice of a convenient material for these supports is critical, because of the required high positioning accuracy of the magnets in their cryostats and stringent thermal budget requirements imposed by the LHC cryogenic system. A glass-fibre/epoxy resin composite has been chosen for its good combination of high stiffness and low thermal conductivity over the 2-293 K temperature range. Plies of long glass-fibres are stacked optimally yielding the best mechanical behaviour. However, heat leaks from the supports are influenced by the thermal characteristics of the composite, which in turn depend on the orientation of the fibres. To study the dependence of the thermal conductivity on fibre's orientation, we performed high precision thermal conductivity measurements of various samples of glass-fibre/epoxy resin composite. The results of the thermal conductivity measurements are compared with integral measurements on support posts for LHC cryomagnets and with mixing models

TRANSPORT AND INSTALLATION OF CRYO-MAGNETS IN CERN'S LARGE HADRON COLLIDER TUNNEL

The arcs of the Large Hadron Collider (LHC) will contain around 1700 main superconducting dipoles and quadrupoles. The long and heavy magnets are supported on fragile composite support posts inside a cryostat to reduce the heat in-leak to the magnets' super fluid helium bath. The presence of fragile components and the need to avoid geometry changes make the cryo-magnets very difficult to handle and transport. The transport and installation of the LHC cryo-magnets in the LEP tunnels originally designed for smaller, lighter LEP magnets has required development of completely new handling solutions. The paper explains the constraints imposed by the cryo-magnet characteristics, the existing tunnel infrastructure and schedule considerations. The development and realisation of transport and handling solutions are described, starting from conceptual design, through manufacture and testing to the installation of the first cryo-magnet. Integration studies to verify and reserve space needed for manoeuvre and the preparation of the infrastructure for transport and installation operations are also presented. The paper includes conclusions and some of the lessons learned

Various methods of manufacturing superconducting accelerating cavities

We report on experience in superconducting cavity production methods gained in shaping, joining and thin film coating with various materials and techniques (Pb, Nb, Nb$_{3}$Sn, NbN, NbTiN) with emphasis on their potential to reduce mass production costs

A Virtual CAD Model of the LHC

Integrating the large and complex LHC machine into the existing LEP tunnel is a major challenge. Space was not really a problem to fit the LEP machine into its tunnel, but LHC cryostats are much larger than the LEP quadrupoles and the external cryogenic line fills even more the tunnel. Space problems lead to small clearances. Possible conflicts, or at least the most penalising ones, between installed equipment or with transport, must be solved beforehand in order to avoid unacceptable delays and extra costs during the installation. Experience gained with LEP has already shown the help that Computer-Aided Engineering tools could provide for the integration. A virtual model of the LHC is presently prepared. The actual LEP tunnel, known with a quite good accuracy (centimetre level), has been modelled and all the elements of the machine constructed as 3D objects with the CAD system are positioned accurately on the basis of data generated from the theoretical definition. These layouts are used to generate the reference sections and to check the clearances. Examples of this powerful approach applied to engineering for accelerators are given

Thermal Design and Performance of the Electrical Distribution Feed Box of the LHC prototype cell

The Electrical Distribution Feed Box (DFBS) is a 4.5 K saturated liquid helium cryostat constructed for the Large Hadron Collider (LHC) Prototype Cell (String 2). The thermal design of the DFBS is presented, with emphasis on the modelling of the cooling of the current lead chimneys via the helium bath boil-off gas and on the design of the lambda plate. The expected performance is compared to measurements done during the first operation phase of the LHC prototype cell