Geometric Field Errors of Short Models for MQXF, the Nb3Sn Low-β Quadrupole for the High Luminosity LHC

Abstract

In the framework of the High-Luminosity upgrade of the Large Hadron Collider, the US LARP collaboration and CERN are jointly developing a 150 mm aperture Nb3Sn quadrupole for the LHC interaction regions. Due to the large beam size and orbit displacement in the final focusing triplet, MQXF has challenging targets for field quality at nominal operation conditions. Three short model magnets have been tested and around thirty coils have been built, allowing a first analysis of the reproducibility of the coil size and turns positioning. The impact of the coil shimming on field quality is evaluated, with special emphasis on the warm magnetic measurements and the correlation to field measurements at cold and nominal field. The variability of the field harmonics along the magnet axis is studied by means of a Monte-Carlo analysis and the effects of the corrective actions implemented to suppress the low order un-allowed multipoles are discussed.

Field Quality of HD3—A Nb<inline-formula> <tex-math notation="LaTeX">$_3$</tex-math> </inline-formula>Sn Dipole Magnet Based on Block Design

“…5). Similar variation of geometric field errors was also observed in the cos 2θ LARP HQ [34] and MQXF magnets for the High-Luminosity LHC [35], [36].…”

Summary of Test Results of MQXFS1—The First Short Model 150 mm Aperture Nb3Sn Quadrupole for the High-Luminosity LHC Upgrade

“…The main goals of the tests included training and examination of its characteristics, magnetic measurements (see [7]) and magnet protection studies (see [8]). …”

Assembly of a Mechanical Model of MQXFB, the 7.2-m-Long Low-<inline-formula> <tex-math notation="LaTeX">$\beta$</tex-math> </inline-formula> Quadrupole for the High-Luminosity LHC Upgrade

“…Positioning errors due to smaller coils can also be corrected, by means of radial and azimuthal (mid-plane) shims. The azimuthal solution is in general preferred, as it allows to bring the four coils inner surface at the same radius, with beneficial effects on the field homogeneity [17]. As a consequence, no shimming was applied on coil C103, and mid-plane shims were applied on the other coils to match its azimuthal size.…”