A Superconducting Permeameter for Characterizing Soft Magnetic Materials at High Fields

Asuperconductingpermeameterisproposedtocharacterizethemagneticpropertiesofhigh-energysuperconducting magnet yokes at their operating temperatureand saturation level. The main problem of superconductingcoils, an undesired quench, was faced by specific protectionsimulations, which has led to a self-protected system. Thesuperconducting permeameter was used to perform the magneticcharacterization of ARMCO Pure Iron, the material for the newHigh-Luminosity Large Hadron Collider (HL-LHC) supercon-ducting magnet yokes, which was performed at the cryogenictemperature of 4.2 K and a saturation level of nearly 3 T.Two case studies based on the new HL-LHC superconductingquadrupole and dipole magnets highlight the impact of themagnetic properties of the yoke on the performance of thesuperconducting magnets, showing that the common assumptionthat heavily saturated steels with similar chemical compositionbehave precisely the same way has been proven wrong

A Metallurgical Inspection Method to Assess the Damage in Performance-Limiting Nb3Sn Accelerator Magnet Coils

The design and production of Nb3Sn-based dipole and quadrupole magnets is critical for the realization of the High-Luminosity Large Hadron Collider (HL-LHC) at the European Organization for Nuclear Research (CERN). Nb3Sn superconducting coils are aimed at enhancing the bending and focusing strengths of accelerator magnets for HL-LHC and beyond. Due to the brittle nature of Nb3Sn, the coil fabrication steps are very challenging and require very careful QA/QC. Flaws in the Nb3Sn filaments may lead to quenches, and eventually, performance limitation below nominal during magnet testing. A novel inspection method, including advanced non-destructive and destructive techniques, was developed to explore the root-causes of quenches occurring in performance-limiting coils. The most relevant results obtained for MQXF coils through this innovative inspection method are presented. This approach allows for precise assessment of the physical events associated to the quenches experienced b y magnet coils, mainly occurring under the form of damaged strands with transversely broken sub-elements. Coil-slice preparation, micro-optical observations of transverse and longitudinal cross-sections, and a deep etching technique of copper will be illustrated in the present work, with a focus on the results achieved for a CERN coil from a non-conforming quadrupole magnet prototype, and two coils fabricated in the US, in the framework of the Accelerator Upgrade Project (AUP) collaboration, from two different non-conforming quadrupole magnets, respectively. The results obtained through the proposed inspection method will be illustrated.Comment: Applied Superconductivity Conference 202

CAS course on "Normal- and Superconducting Magnets", 19 November - 02 December 2023, St. Pölten, Austria

The production of superconducting magnets for accelerators is a complex and not yet fully industrialised process. Ensuring the reliable performance of these magnets in accelerators requires meticulous engineering across a diverse range of specialties. In this lecture, after a brief historical overview of accelerator magnets design and construction, we review the main manufacturing steps for the construction of an accelerator magnet, from the strand to the cryostat. We take as examples the NbTi 8.3 T dipoles for the LHC and the Nb3Sn 11.3 T quadrupoles for HL-LHC, putting in evidence the differences in between the two technologies. The main features of the magnets are reviewed, showing how the design and component quality impact on construction and why the final product calls for a total-quality approach. Finally, we briefly review why, what, and how we test superconducting magnets, underlining the close connection with the design validation and with the manufacturing process

Quench Modeling in High-field Nb3_3Sn Accelerator Magnets

The development of high-field magnets is on-going in the framework of the LHC luminosity upgrade. The resulting peak field, in the range of 12 T to 13 T, requires the use Nb$_{3}$Sn as superconductor. Due to the high stored energy density (compact winding for cost reduction) and the low stabilizer fraction (to achieve the desired margins), quench protection becomes a challenging problem. Accurate simulation of quench transientsin these magnets is hence crucial to the design choices, the definition of priority R&D; and to prove that the magnets are fit for operation. In this paper we focus on the modelling of quench initiation and propagation, we describe approaches that are suitable for magnet simulation, and we compare numerical results with available experimental data