The standard Instrumentation Feedthrough System for the LHC cryo-magnets

For the LHC, 1232 dipole magnets and about 400 quadrupole magnets operating at 1.9 K are installed in arcs and dispersion suppressors. Each cryo-magnet assembly comprises the main magnet and several small corrector magnets. Each assembly is equipped with voltage taps, quench heaters and cryogenic instrumentation. The number of instrumentation wires serving each magnet assembly and passing from cold to ambient is between 36 and 40. An Instrumentation Feedthrough System (IFS) will electrically and mechanically connect the instrument wires to the outside of the vacuum vessel. The IFS has to satisfy several requirements: simplicity of integration, optimal access during tests and commissioning, voltage withstand and reliability during the lifetime of the machine. The heat load to superfluid helium must be minimized, and the long-term stability of the insulation vacuum should be preserved. The solution foresees an open stainless steel tube housing the wires connected between the magnet and the outside of the vacuum vessel and terminated by a leak tight connector. The IFS is assembled from different standard components designed to fulfil the electrical, mechanical and thermal requirements and will be integrated by the industries that build the magnets. The standardization of the IFS for all types of cryo-magnet assemblies permits the same hardware interfaces and procedures to be used from the integration to commissioning and operation of the machine. This paper describes the main parameters, the technical choices, the performance and the integration techniques of the IFS system.