The Role of Azimuthal Prestress in the Longitudinal Degradation of Nb₃Sn Superconducting Magnets

Journal Article · Tue Dec 17 00:00:00 EST 2024 · IEEE Trans.Appl.Supercond.

DOI:https://doi.org/10.1109/TASC.2024.3519079· OSTI ID:2504182

Vallone, G. ^[1]; Ambrosio, G. ^[2]; Anderssen, E. ^[1]; Ferracin, P. ^[1]

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1. LBL, Berkeley
2. Fermilab

Superconducting magnet coils are subject to enormous electro-magnetic forces which push the cables away from the winding pole, and against the surrounding structure. This structure is usually optimized trying to limit the overall motion and the strains experienced by the superconducting elements. To achieve this, preload forces are applied both in the coil cross-section and along its length. If the e.m. forces overcome these preloads, separation between the coil and the pole occurs, resulting in an overall loss of rigidity. During the magnet design process, it is often tempting to treat the optimization of the azimuthal and longitudinal preload systems separately. However, the two are inextricably related: as the cross-section preload increases, friction can prevent any motion in the longitudinal plane, and decreasing it can instead allow dangerous motions in the conductor ends. The latter can result in very high strains and, in Nb₃Sn conductors, damage that can prevent the magnet to reach the desired performances. In an attempt to define design guidelines, in this paper we use simplified numerical models to compute, as a function of the in-plane prestress, the variation of the peak strains in the end region of the coils. Finally, we investigate the impact of the azimuthal prestress on a real magnet case, the High-Luminosity Nb₃Sn Quadrupole MQXF.

• Research Organization: Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: US Department of Energy
• Grant/Contract Number: 89243024CSC000002; AC02-07CH11359
• OSTI ID: 2504182
• Report Number(s): FERMILAB-PUB-24-0947-TD; oai:inspirehep.net:2866870
• Journal Information: IEEE Trans.Appl.Supercond., Journal Name: IEEE Trans.Appl.Supercond. Journal Issue: 5 Vol. 35
• Country of Publication: United States
• Language: English

Related Subjects

Nb3Sn
accelerator magnets
mechanical aspects
preload