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A first series of six LHC 10 m long prototype dipole magnets and cryostats have been manufactured in European Industry and the assembled cryo-magnets tested singly and connected in series in a test string at CERN between March 1994 and December 1996. During the same period, an evolution in the requirements for LHC cryogenics distribution has lead the project management to adopt a separate cryo-distribution line running parallel to the LHC machine 1. The former standard LHC half-cell, made up of a short straight section unit and four 10 m dipoles, has been discarded and replaced with one composed of a short straight section unit and three 15 m dipoles. The new 15 m LHC dipole magnet cryostats are described. These units house the dipole magnet cold mass standing on three low heat in-leak support columns, and enclosed within an actively cooled radiation screen operating at 4.5-20 K and an actively cooled thermal shield operating at 50-75 K.

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Forty-four kilometers of the LHC beam vacuum system [1,2] will be equipped with a perforated co-axial liner, the so-called beam screen. Operating between 5 K and 20 K, the beam screen reduces heat loads to the 1.9 K helium bath of the superconducting magnets and minimises dynamic vacuum effects. Constructed from low magnetic permeability stainless steel with a 50 µm inner layer of high purity copper, the beam screen must provide a maximum aperture for the beam whilst resisting the induced forces due to eddy currents at magnet quench. The mechanical engineering challenges are numerous, and include stringent requirements on geometry, material selection, manufacturing techniques and cleanliness. The industrial fabrication of these 16 metre long UHV components is now in its prototyping phase. A description of the beam screen is given, together with details of the experimental programme aimed at validating the design choices, and results of the first industrial prototypes. LHC and EST DivisionsPresented at 1997 Particle Accelerator Conference, Vancouver,[12][13][14][15][16] AbstractForty-four kilometers of the LHC beam vacuum system [1,2] will be equipped with a perforated co-axial liner, the so-called beam screen. Operating between 5 K and 20 K, the beam screen reduces heat loads to the 1.9 K helium bath of the superconducting magnets and minimises dynamic vacuum effects. Constructed from low magnetic permeability stainless steel with a 50 µm inner layer of high purity copper, the beam screen must provide a maximum aperture for the beam whilst resisting the induced forces due to eddy currents at magnet quench. The mechanical engineering challenges are numerous, and include stringent requirements on geometry, material selection, manufacturing techniques and cleanliness. The industrial fabrication of these 16 metre long UHV components is now in its prototyping phase. A description of the beam screen is given, together with details of the experimental programme aimed at validating the design choices, and results of the first industrial prototypes.

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