Design of the Second Series of LHC Prototype Dipole Magnet Cryostats

An initial series of six LHC 10 m long prototype dipole magnets and cryostats have been manufactured by European Industry. The assembled cryo-magnets were 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 project management to adopt a seChapaute cryo-distribution line running Chapaullel 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, which stands on three low heat in-leak support columns, and is enclosed within an actively cooled radiation screen operating at 4.5–20 K and an actively cooled thermal shield operating at 50–75 K.