An MgB2 superconducting shield prototype for the Future Circular Collider septum magnet

Barna, Daniel and Giunchi, Giovanni and Novak, Martin and Brunner, Kristof and Nemet, Aniko and Petrone, Carlo and Atanasov, Miroslav Georgiev and Bajas, Hugues and Feuvrier, Jerome (2019) An MgB2 superconducting shield prototype for the Future Circular Collider septum magnet. IEEE Transactions on Applied Superconductivity. p. 1. ISSN 1051-8223 (In Press)

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Abstract

A passive superconducting shield was previously proposed to realize a high-field (above 3 T) septum magnet for the Future Circular Collider proton-proton ring (FCC-hh). This paper presents the experimental results of a potential shield material, MgB2 at a temperature of 4.2 K. A cylindrical shield with a wall thickness of 8.3 mm was manufactured by the reactive liquid magnesium infiltration technique using extra large grain (∼160 µm) boron precursor, and tested in a transverse magnetic field. The shield was stable against flux jumps on the virgin curve, but suffered from flux jumps at low field levels after high-field exposure. The tube could shield a magnetic field of 2.75 T on its surface before field penetration to its interior. Parameters of the critical current density of the material could be estimated from simulations, which indicate a steeper Jc(B) curve than observed previously for large grain (∼100 µm) MgB2, and predict a slightly better shielding performance (3 T) with an ideal geometry. Relaxation of the shielding currents is at an acceptable level. We estimate that a self-supporting shield of a wall thickness of 14 mm could be adequate for the construction of a 3 T septum magnet, if the flux jump problem can be solved. This thickness would correspond to a total septum thickness (including beam pipes, etc) of around 22 mm, which is an acceptable figure for the FCC-hh.

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