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Description
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 installed 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. Magnetic measurements are confined to be within the 100 mm diameter of the anti-cryostat used for cold testing, but the aperture is reduced to 46 mm at the cryogenic feed box of the test stand – further complicating both the alignment and rotating coil measurements. To accurately determine rotating coil location and angles within the cold mass, a laser tracker is employed to record multiple targets at one end of the probe, deep within the anti-cryostat.
This paper describes the measurements, probes/equipment, and techniques used to perform the necessary characterization of the cold mass.
