A rotating coil measurement system based on CMM for high-gradient small-aperture quadrupole in HEPS-TF

Purpose A new rotating coil measurement system based on the coordinate measurement machine (CMM) is developed for measuring high-gradient small-aperture quadrupole magnet in the Test Facility of High Energy Photon Source (HEPS-TF).
Methods The CMM and two groups of Newport translate stages are combined to align the rotating coil relative to the magnet mechanical center. A high precision ceramic skeleton with bucked coil is made as a measurement sensor. The integrated field gradient, harmonics, magnetic center offset and excitation curve of a high-gradient small-aperture quadrupole prototype magnet are measured.
Results The rotating coil is aligned to the magnet mechanical center within 10 μm. The reproducibility of higher harmonics is within 0.2 × 10^-4. The repeatability of the magnet center in horizontal direction is under 1.5 μm, while that in vertical direction is less than 2.5 μm in different days. The architecture of the measurement system, the measuring procedure and some primary results of the quadrupole prototype magnet are illustrated in this paper.
Conclusion A rotating coil measurement system based on CMM has been well developed, and the collimation efficiency and precision are improved. The harmonic changes caused by iron fingers are measured by the measurement system. The difference between the measurement result and the OPERA-3D simulation result is less than 0.5 × 10^-4. The performance of this measurement system can meet the magnet measurement requirements of HEPS-TF.