Magnetic Measurements of HL-LHC AUP Cryo-Assemblies at Fermilab

TL;DR

This paper details the magnetic measurement techniques and equipment used to assess the magnetic performance and alignment of cryogenic assemblies for the HL-LHC upgrade at Fermilab, ensuring they meet strict specifications.

Contribution

It introduces a comprehensive measurement approach combining rotating coil, wire systems, and laser tracking for precise characterization of cryogenic magnet assemblies.

Findings

Successful magnetic field measurements at 1.9 K

Accurate determination of magnetic axis and field harmonics

Validation of assembly performance against specifications

Abstract

LQXFA/B production series cryogenic assemblies are being built for the LHC upgrade by the HL-LHC Accelerator Upgrade Project (AUP). These contain a pair of MQXFA quadrupole magnets combined as a cold mass within a vacuum vessel, and are to be installed in the IR regions of the LHC. The LQXFA/B are being tested at 1.9 K to assess alignment and magnetic performance at Fermilab's horizontal test facility. The ~10 m - long assembly must meet stringent specifications for quadrupole strength and harmonic field integrals determination, magnetic axis location, and for variations in axis position and local field profile. A multi-probe, PCB-based rotating coil and Single Stretched Wire system are employed for these measurements. To accurately determine rotating coil location and angles within the cold mass, a laser tracker is utilized to record multiple targets at one end of the probe. This paper describes the measurements, probes/equipment, and techniques used to perform the necessary characterization of the cold mass.