This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/TASC.2017.2651358, IEEE Transactions on Applied Superconductivity 2LPo2B-09 1 Magnetic Analysis of the Nb 3 Sn low-beta Quadrupole for the High Luminosity LHC S. Izquierdo Bermudez, G. Ambrosio, G. Chlachidze, P. Ferracin, E. Holik, J. Di Marco, E. Todesco, G.L. Sabbi, G. Vallone, X. Wang. Abstract — As part of the Large Hadron Collider Luminosity TABLE I M AIN D IMENSIONAL P ARAMETERS FOR MQXFS1 upgrade (HiLumi-LHC) program, the US LARP collaboration and CERN are working together to design and build 150 mm Parameter Unit aperture Nb 3 Sn quadrupoles for the LHC interaction regions. A Cable bare width (before/after HT) mm 18.150/18.513 first series of 1.5 m long coils were fabricated, assembled and Cable bare mid-thick. (before/after HT) mm 1.525/1.594 tested in the first short model. This paper presents the magnetic Keystone angle Deg. 0.55 analysis, comparing magnetic field measurements with the Cable pitch length mm 109 expectations and the field quality requirements. The analysis is Cable core width mm 12 focused on the geometrical harmonics, iron saturation effect and Cable core thickness µm 25 cold-warm correlation. Three dimensional effects such as the Cable insulation thickness per side at 5 MPa µm 150±5 variability of the field harmonics along the magnet axis and the Coil clear aperture diameter mm 150 contribution of the coil ends are also discussed. Moreover, we No. turns in layer 1/2 (octant) -- 22/28 present the influence of the conductor magnetization and the Magnet (LHe vessel) outer diameter mm 630 dynamic effects. Magnetic length mm 1194 Overall coil length mm 1510 Index Terms — High Luminosity LHC, Field Quality, Magnetic Magnetic yoke length mm 1550 Measurements, High Field Nb 3 Sn Magnet. Coil 5 Coil 104 I. I NTRODUCTION T HE high luminosity LHC upgrade aims at increasing the integrated luminosity of the LHC by a factor of 10 beyond its nominal performance expected for 2023 [1]. Part of the upgrade relies on the replacement of the single aperture quadrupoles in the interaction region (the so called low- β or inner triplet quadrupoles). The design, referred as MQXF, foresees a 150 mm aperture quadrupole based on Nb 3 Sn technology [2]. The first MQXF short model (MQXFS1a) has been assembled in LBNL [4] and tested at FNAL [5], using two coils produced by LARP (coils 3 and 5) and two coils produced by CERN (coils 103 and 104). The four coils are made using OST Restacked-Rod-Process (RRP) Nb 3 Sn wires, using Coil 3 Coil 103 108/127 stack for LARP coils and 132/169 stack for CERN coils. This paper presents the results and analysis of the Fig. 1. Magnet cross section viewed from the lead end, including the position magnetic measurements performed on MQXFS1a. of each coil in the magnet assembly. currents. The operational gradient in nominal conditions is II. M AGNET D ESIGN 132.6 T/m with a peak field in the conductor of 11.4 T and a current of 16.48 kA, with an operating temperature of 1.9 K. The cross-section of the MQXF quadrupole magnet is shown The physical length of the coil is 1510 mm, corresponding to a in Fig. 1 and the main dimensional parameters of the magnet magnetic length of about 1.2 m and a good field quality region are summarized in Table I. The two layer coils are made with a Rutherford-type cable composed of 40 strands of 0.85 mm of 500 mm [6]. The coils are assembled inside a support structure based on an external aluminum shell pre-loaded with diameter. The cable incorporates a 12-mm-wide stainless steel core of 25 μm thickness to reduce inter-strand coupling bladders and keys [7]. Automatically generated dates of receipt and acceptance will be placed here; G. Ambrosio, G. Chlachidze, E.Holik and J. Di Marco are with Fermi Work supported by the USA-DoE and by the High Luminosity LHC project at National Accelerator Laboratory (FNAL), Batavia, IL 60510 USA. CERN. G.L. Sabbi and X. Wang are with Lawrence Berkeley National Laboratory S. Izquierdo Bermudez, P. Ferracin, E.Todesco and G. Vallone are with (LBNL), Berkley, CA 94720 USA. CERN, 1211 Geneva, Switzerland (email: susana.izquierdo.bermudez@cern.ch). 1051-8223 (c) 2016 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.
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