Fabrication and Test of the Fourth Prototype of the D2 Orbit Corrector Dipole for HL-LHC

As part of the High-Luminosity upgrade project (HL-LHC) for the Large Hadron Collider (LHC) at CERN, new double-aperture beam orbit corrector magnets will be installed near the recombination dipole (D2). These magnets are 2.2 m long Nb–Ti dipoles based on the Canted Cosine-Theta (CCT) design. They provide an in bore magnetic field of 2.60 T at 394 A in a 105 mm aperture with an integrated field of 5 Tm. The fourth full-length prototype was built and tested at CERN. Its design is based on the best engineering practices from previous prototypes. In this paper we first report on recent improvements in the manufacturing process, focusing on the feedback from winding and on the optimization of the impregnation phase. The magnetic measurements carried out at warm and cold temperatures are then reported. Finally, the results of powering tests at 1.9 K and 4.5 K are presented. The magnet meets the dimensional, electrical and magnetic requirements, and is a valid reference for the HL-LHC series production that is currently being carried out in collaboration between CERN and IHEP.