Summary of the Mechanical Performances of the 1.5 m Long Models of the Nb<inline-formula> <tex-math notation="LaTeX">$_{3}$</tex-math> </inline-formula>Sn Low-<inline-formula> <tex-math notation="LaTeX">$\beta$</tex-math> </inline-formula> Quadrupole MQXF

Abstract

The Nb 3 Sn quadrupole MQXF is being developed as a part of the LHC High Luminosity upgrade. The magnet design was tested on 1.5 m long short models, sharing the same cross-section with the full-length magnets. Various azimuthal and longitudinal preloads were applied, studying the impact on the magnet training and on its mechanical performances. The experiments demonstrated the possibility to control the magnet prestress. However, various factors, coil size among the others, may affect the stress variation between and within each winding. This variation could prevent the magnet to reach the desired performances, for example as result of critical current degradation of the Nb 3 Sn strands. This paper analyzes the mechanical performances of the short models, studying in particular the stress variation on different coils. The measured coil size was used as input in the numerical simulations, and results were then compared with the strain gauge measurements. Finally, the short models experience was used to evaluate the feasibility of a loading operation that does not rely on the strain measurements.

A methodology for the analysis of the three-dimensional mechanical behavior of a Nb3Sn superconducting accelerator magnet during a quench

“…Both two-dimensional and three-dimensional mechanical models were developed for MQXF well before this work (see figure 7), and extensively validated during the test campaign of short model magnets [79][80][81][82][83][84][85][86][87][88]. Structural elements are used to mesh the different magnet components, where the geometry of the conductor blocks (composed of many cable turns) is simplified as a homogenized solid volume.…”

“…On the contrary, the posterior decrease is not observed in the test results. longitudinal direction, it is established by the axial pre-tension of the tie rods with a force that corresponds to 100% of the expected e.m. load [84].…”