Electrical and magnetic performance of the LHC short straight sections

Abstract

The Short Straight Section (SSS) for the Large Hadron Collider arcs, containing in a common cryostat the lattice quadrupoles and correction magnets, have now entered series production. The foremost features of the lattice quadrupole magnets are a two-in-one structure containing two 56 mm aperture, two-layers coils wound from 15.1 mm wide NbTi cables, enclosed by the stainless steel collars and ferromagnetic yoke, and inserted into the inertia tube. Systematic cryogenic tests are performed at CERN in order to qualify these magnets with respect to their cryogenic and electrical integrity, the quench performance and the field quality in all operating conditions. This paper reports the main results obtained during tests and measurements in superfluid helium. The electrical characteristics, the insulation measurements and the quench performance are compared to the specifications and expected performances for these magnets. The field in the main quadrupole is measured using three independent systems: 10-m long twin rotating coils, an automatic scanner, and single stretched wire. A particular emphasis is given to the integrated transfer function which has a spread of around 12 units rms in the production and is a critical issue. The do-decapole harmonic component, which required trimming through a change in coil shims, is also discussed. Finally, the magnetic axis measurements at room temperature and at 1.9 K, providing the nominal vertical shift for installation are reported.