Mechanical design and layout of the LHC standard half-cell

The LHC Conceptual Design Report issued on 20th October 1995 introduced significant changes to some fundamental features of the LHC standard half-cell, composed of one quadrupole, 3 dipoles and a set of corrector magnets. A separate cryogenic distribution line has been adopted containing most of the distribution lines previously installed inside the main cryostat. The dipole length has been increased from 10 to 15 m and independent powering of the focusing and defocusing quadrupole magnets has been chosen. Individual quench protection diodes were introduced in magnet interconnects and many auxiliary bus bars were added to feed in series the various families of superconducting corrector magnets. The various highly intricate basic systems such as: cryostats and cryogenics feeders, superconducting magnets and their electrical powering and protection, vacuum beam screen and its cooling, support acid alignment devices have been redesigned, taking into account the very tight space available. These space constraints are imposed by the desire to have maximum integral bending field strength for maximum LHC energy, in the existing LEP tunnel. Finally, cryogenic and vacuum sectorisation have been introduced to reduce downtimes and facilitate commissioning.