The High-Luminosity LHC (HL-LHC) project aims at upgrading the existing LHC machine to increase its integrated luminosity by a factor of ten. A key aspect of this upgrade is the inner triplet (or low-β) quadrupole magnets, the MQXF, which utilize Nb3Sn superconducting magnet technology and reach a conductor peak field of 11.3 T. The MQXFB version, manufactured at CERN, is characterized by a magnetic length
of 7.2 m, making it the longest Nb3Sn accelerator magnet ever realized. A total of 10 MQXFB series magnets are needed for HL-LHC (8 to be installed and 2 spares). The magnet relies on a system of water pressurized bladders and keys to pre-tension the aluminium shrinking cylinder at room temperature and to apply pre-stress to the coil-pack. The coil pre-load increases after cool-down to 1.9 K thanks to the larger thermal contraction of the aluminium shrinking cylinder with respect to the rest of the magnet components. Since this structural design is used for first time in an accelerator magnet, the accumulated experience of assembling 80% of the magnets provides valuable insights for the potential application of Nb3Sn technology in future colliders. The main measurables for the mechanical assembly of the MQXFB series magnets and asses the reproducibility of the production are presented in this seminar. The main lessons learned during the fabrications process are also described.
