Ezio Todesco

During the Long Shutdown 3 of the LHC, scheduled to start in 2026, the interaction regions will be upgraded to increase the integrated luminosity by about one order of magnitude. Among the components to be replaced are the MBRD (Main Bending Recombination Dipole, also known as D2), which are double-aperture magnets providing aligned magnetic fields to steer the two beams into the ATLAS and CMS experiments and subsequently recombine them onto their nominal trajectories. To meet the demanding requirements of the High-Luminosity LHC, a new magnet design was developed by INFN-Genova, featuring a larger aperture, a higher operating field, and innovative solutions to mitigate the strong electromagnetic cross-talk between the apertures while ensuring mechanical integrity against the large repulsive Lorentz forces. The development program included the construction of a 1.6-m model, a full-length prototype, and six series magnets, of which four will be installed in the LHC and two kept as spares. Series production is ongoing at ASG Superconductors, and the first magnet has been successfully cold-tested at CERN. This contribution reports on the main challenges faced during series production and discusses the first test results.

The FalconD project (Future Accelerator post-LHC Optimized Nb$_{3}$Sn Dipole), conducted by INFN Genoa and Milan in collaboration with CERN, is dedicated to the development of a 1.5 m long, 12 T Nb$_{3}$Sn dipole. Nb$_{3}$Sn has already proven its effectiveness in accelerator magnets, and its application to bending dipoles is a key step toward future high-field accelerator technologies. A major challenge of the design is the mechanical structure, which must withstand the substantial Lorentz forces generated by the high magnetic field. To address this, the innovative bladder and key (B $\text{&}$ K) concept is adopted, applied here for the first time to a cos-theta dipole. This contribution presents a 2D finite element mechanical analysis of the FalconD, focusing on stress distribution and gap evolution during the main assembly and operational stages, with the aim of validating the design approach.

As part of the high field magnet programme at CERN, the Nb₃Sn block coil configuration is a candidate for the main dipole in future large hadron collider as FCC-hh. To reduce the cost, the use of material grading in the block coil is explored by using an Nb–Ti conductor instead of Nb₃Sn in the external low-field regions. Different designs are being investigated for dipoles with a target nominal field of 14 and 12 T. The gain in conductor as well as in ac-losses are reported, together with consideration on operational temperature (1.9 K versus 4.5 K). Finally, the preliminary design of an Nb₃Sn/Nb–Ti short model coil is presented as a first proof of such a concept of hybrid technology in block coils.

The FalconD (Future Accelerator post-LHC Cos-$\theta$ Optimized ${\mathrm{Nb}}_{3}$Sn Dipole magnet is part of the High Field Magnet (HFM) CERN programme. In collaboration with the Italian Institute for Nuclear Physics (INFN Genova and LASA Milano), CERN is developing a ${\cos \theta }$ dipole magnet beyond 12 T based on proven ${\mathrm{Nb}}_{3}$Sn technology in the MQXF quadrupole used in the high-luminosity upgrade of the LHC. The magnet, with design aperture diameter of 50 mm, provides a bore field of 12 T for a 73 TeV center-of-mass energy scenario for the Future FCC-hh Circular Collider. The project has specific objectives to investigate cos-$\theta$ short magnet model design based on a two-layers coil with a wide high current cable. Moreover, the study of mechanical dipole structures based on aluminum shell with bladders and key (B&K) developed for the HL-LHC MQXF quadrupole will be presented as a baseline. The structure pre-loading system assembly baseline shall be tested on sub-scale mechanical mock ups at 77 K prior to building two single aperture 1.5 m long ${\mathrm{Nb}}_{3}$Sn magnet models followed by a 2-in-1 dipole magnet assembly. In this paper, we provide an overview of the magnetic and structural design carried out at CERN on an increased aperture diameter variant supported by first preliminary winding trials and give insights of the project timeline. Some preliminary protection scheme assessment is presented as baseline to be tested. Following the cable winding outcomes and the mechanical properties measured, some alternative coil optimized magnetic cross-section is reported.

MCBXF magnets are orbit correctors for the High-Luminosity (HL) Large Hadron Collider (LHC) upgrade. The magnet design consists of two nested dipoles, with an aperture of 150 mm, which is described elsewhere. The magnets have been designed in two physical lengths, namely of 2.5 m (MCBXFA) and 1.5 m (MCBXFB), with the same cross section. The series production of the magnets consists of 5 long and 10 short magnets. The component production is being carried out at CIEMAT and magnet assembly is made at CERN. This paper summarizes the results of the magnetic measurements of the short magnets produced so far, including warm magnetic measurements. The first magnets featured repetitive results regarding field quality. Afterwards, some of the magnets showed a shift of the main harmonics. After careful analysis of the fabrication steps, it was found out that the impregnation mold assembly strategy impacted on the coil dimensions. The shimming plan was tuned to deal with this feature, and the field quality was enhanced accordingly.

A series production of beam separation dipole, MBXF, is underway toward the High-Luminosity Large Hadron Collider upgrade (HL-LHC). So far, High Energy Accelerator Research Organization (KEK) have tested 4 series magnets in our own vertical cryostat, and their quench training performances have been successfully evaluated. The results show different training behaviors, and particularly MBXF3 has a slower training rate even after the thermal cycle (TC). Quench-antenna (QA) signals for such the magnet shows a prominent oscillatory pattern due to mechanical disturbance. In order to understand origin of the different training behaviors, a new data-acquisition system has been introduced to detect QA activities during powering the magnet. The system was first demonstrated in the second cooldown (CD) of MBXF5 (Apr. - May ’25), and the training evolution became clearly visible: Mechanical activities cease with each training cycle while appearance of the activities was confirmed after TC indicating loss of the training memory. We expect that this new detection tool can help to understand the reason of the different training rate, and thus it will be used for rest of the MBXF tests.

Building on the initial magnetic design of DAISY, the 14 T common coil magnet demonstrator being developed at CIEMAT under the High Field Magnet (HFM) programme, this paper investigates the feasibility of hybrid designs combining Nb₃Sn and NbTi for high- and low-field regions, respectively. The primary goal is to minimise superconductor usage while ensuring that the magnet meets the functional requirements of future collider applications, such as the Future Circular Hadron Collider (FCC-hh). The study examines the potential to achieve accelerator-grade field quality without ancillary coils and to maintain minimal multipole variation between low and nominal currents, highlighting the trade-offs in superconductor efficiency. Comparisons are made with all Nb₃Sn designs, including magnet protection, to identify the relative advantages and limitations of hybrid layouts. The results offer valuable insights into optimising superconductor usage and refining design strategies for next-generation high-field common coil magnets, addressing the unique challenges associated with hybrid configurations.

The Falcon Dipole is a project led by the Italian Institute of Nuclear Physics (INFN), which aims tofabricate a 12 T short model of a Nb$_{3}$Sn cos-theta accelerator dipole as part of the High Field Magnet (HFM) R&D program at CERN [1]. The status of the project is at the fabrication step of the first dummy coil in the industry and, in this paper, the results of the first campaign of winding tests conducted in the industry are presented. The winding process for the Falcon Dipole is challenging because the size of the Rutherford Cable used for the coils is comparable to the bore radius. This results in high bending and torsion stresses, making the cable structure unstable. To address these challenges, the previous 3D model has been modified to improve the winding feasibility. The setup has been prepared to monitor technical parameters that will help in modeling the coil geometry and identifying sources of critical issues. In this paper, the outcomes of the winding campaign are reported and the proposed changes to the coil end design to address the issues that arose are discussed.

At the heart of the High-Luminosity Project (HL-LHC) to upgrade the CERN Large Hadron Collider (LHC), new Nb$_{\text{3}}$Sn superconducting quadrupole magnets will be installed on each side of the ATLAS and CMS experiments. Half of these magnets are built by CERN and are called MQXFB. A total of 12 MQXFB magnets are being constructed for installation: two to be installed in the Inner Triplet (IT) String facility, for systems qualification; four to be installed in the LHC near ATLAS; four to be installed in the LHC near CMS, and two spare magnets. In the last two years, the first seven MQXFB magnets have been tested and qualified up to nominal current in nominal operating conditions. In this paper we present the tests and analyze the magnets’ performance, with emphasis on qualification, non-conformity detection, and reliability evaluation.