CERN Accelerating science

Article
Report number	FERMILAB-PUB-22-858-TD
Title	A Novel Design for Improving the Control on the Stainless-Steel Vessel Welding Process for Superconducting Magnets
Author(s)	Vallone, G (LBL, Berkeley) ; Ambrosio, G (Fermilab) ; Anderssen, E (LBL, Berkeley) ; Fehrer, S (Fermilab) ; Ferracin, P (LBL, Berkeley) ; Ferradas Troitino, J (CERN)
Publication	2023
Imprint	2022
Number of pages	5
In:	IEEE Trans. Appl. Supercond. 33 (2023) 4001705
DOI	10.1109/TASC.2023.3249646
Subject category	Accelerators and Storage Rings
Accelerator/Facility, Experiment	CERN LHC
Project	CERN HL-LHC
Abstract	Stainless steel vessels see widespread use in superconducting magnets for particle accelerator applications. Their function varies in different magnet designs: they always provide the necessary liquid helium containment, but in some cases are also used to provide azimuthal prestress and can also be welded to the magnet end plate to provide additional longitudinal stiffness. A magnet designed with the bladder and key technology does not rely on the structural role of the vessel. They are structurally supported using azimuthally prestressed aluminum shells, and the longitudinal constraint by rods. In this case, the magnet designer would generally like to minimize the interaction between the magnet and the stainless-steel vessel and to minimize the coil stress variation due to the vessel. The stress state in the vessel and in the coil is a function of the circumferential interference, defined as the vessel azimuthal length minus the magnet circumference. The vessel and the magnet azimuthal length machining tolerances are relatively large resulting in significant stress variations in the superconducting coils. In this paper we introduce an interference control shim, which can significantly limit the stress variation of the coils for a given variation of the interference. The effectiveness of the interference-control shim is evaluated numerically on the MQXF, the low-β quadrupole for the High Luminosity LHC.
Copyright/License	publication: © 2023-2025 IEEE

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