Magnetic Field Measurements of LHC Inner Triplet Quadrupoles Fabricated at Fermilab

Abstract

Abstract-Fermilab, as part of the US-LHC AcceleratorProject, is producing superconducting low-beta quadrupole magnets for the Large Hadron Collider (LHC). These 5.5 m long magnets are designed to operate in superfluid helium at 1.9 K with a nominal gradient of 205 T/m in the 70 mm bore. Two quadrupoles separated by a dipole orbit corrector in a single cryogenic assembly comprise the Q2 optical elements of the final focus triplets in the LHC interaction regions. The field quality of the quadrupoles is measured at room temperature during construction of the cold masses as well as during cold testing of the cryogenic assembly. We summarize data from the series measurements of the magnets and discuss various topics of interest.

Magnetic Analysis of the Nb3Sn Low-Beta Quadrupole for the High-Luminosity LHC

“…9 shows the measured decay of the dodecapole. The amplitude of the decay is 0.4 units, which is very close in amplitude and direction to the decay observed in HQ02 and HQ03 models [17] and comparable to the decay observed in Nb-Ti magnets [18]. The data can be fitted using a single exponential with a time constant of 540 s.…”

Field Quality Measurements and Analysis of the LARP Technology Quadrupole Models

“…9), while the average amplitude in the MQXB NbTi quadrupoles was found to be 0.39±0.11 [2]. The long-term decay and snap-back was not observed also in other Nb 3 Sn magnets made of similar conductors.…”

“…These quadrupoles aim to substitute the recently built by Fermilab and KEK LQX [2]- [3] NbTi based LHC IR magnets. They have to provide similar or better operational parameters: more than 205 T/m at large aperture of 90 mm with excellent field quality for smaller beta-star and most important to sustain the high radiation conditions of the IRs.…”

Field Quality Study of the LARP ${\rm Nb}_{3}{\rm Sn}$ 3.7 m-Long Quadrupole Models of LQ series

“…In comparison, the average dodecapole snapback amplitude in the NbTi LHC IR quadrupoles was found to be 0.39 0.11 [12]. This difference could be attributed to the larger filament size and the production process between the and NbTi cables.…”

“…The characteristic of this profile is summarized in [12]; the most important parameter is the duration of the injection plateau, which was set to 900 s. Our analysis was performed on the normal and components, the first two allowed multipoles. Fig.…”