CERN Accelerating science

Article
Report number	arXiv:1809.04330
Title	NbTi/Nb/Cu multilayer shield for the superconducting shield (SuShi) septum
Author(s)	Barna, D. (Wigner RCP, Budapest) ; Novák, M. (Wigner RCP, Budapest) ; Brunner, K. (Wigner RCP, Budapest) ; Petrone, C. (CERN) ; Atanasov, M. (CERN) ; Feuvrier, J. (CERN) ; Pascal, M. (CERN)
Publication	2018-10-02
Imprint	2018-09-12
Number of pages	8
In:	IEEE Trans. Appl. Supercond. 29 (2018) 4900108
DOI	10.1109/TASC.2018.2872860 (publication)
Subject category	physics.acc-ph ; Accelerators and Storage Rings
Abstract	A passive superconducting shield was proposed earlier to realize a high-field (3-4 T) septum magnet for the Future Circular Collider. This paper presents the experimental results of a potential shield material, a NbTi/Nb/Cu multilayer sheet. A cylindrical shield was constructed from two halves, each consisting of 4 layers with a total thickness of 3.2 mm, and inserted into the bore of a spare LHC dipole corrector magnet (MCBY). At 4.2 K, up to about 3.1 T at the shield's surface only a leakage field of 12.5 mT was measured inside the shield. This can be attributed to the mis-alignment of the two half cylinders, as confirmed by finite element simulations. With a better configuration we estimate the shield's attenuation to be better than $\mathbf{4\times 10^{-5}}$, acceptable for the intended application. Above 3.1 T the field penetrated smoothly. Below that limit no flux jumps were observed even at the highest achievable ramp rate of more than 50 mT/s at the shield's surface. A 'degaussing' cycle was used to eliminate the effects of the field trapped in the thick wall of the shield, which could otherwise distort the homogeneous field pattern at the extracted beam's position. At 1.9 K the shield's performance was superior to that at 4.2 K, but it suffered from flux jumps.
Copyright/License	preprint: (License: arXiv nonexclusive-distrib 1.0)

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