Design, Fabrication, and Magnetic Measurement of the Storage Ring Magnet System for the Hefei Advanced Light Facility

Abstract The Hefei Advanced Light Facility (HALF) is a fourth-generation synchrotron light source under construction. Its 2.2 GeV diffraction-limited storage ring is designed for a natural emittance below 85 pm·rad and uses a compact hybrid multi-bend achromat lattice with 880 production magnets distributed over 20 cells. The dense lattice imposes tightly coupled requirements on the storage-ring magnet system, including short magnetic lengths, relatively large apertures and good-field regions, wide field or gradient tuning ranges, and stringent control of integrated field quality and normalized multipole components. This paper reports the component-level design, fabrication, and factory magnetic-measurement validation of the HALF storage-ring magnet system, including electromagnetic variable-gap longitudinal-gradient bending magnets (LGBs), quadrupoles, reverse-bend dipole–quadrupole combined-function magnets (RB magnets), sextupoles, octupoles, and slow and fast correctors. The LGBs were designed using a trajectory-based procedure that simultaneously controls the stepwise longitudinal field profile, first and second field integrals, integrated-field homogeneity along the actual trajectory, trajectory deviation, and magnet-to-magnet consistency for series operation. The multipole magnets were optimized using finite-element pole-profile workflows based on conformal mapping, Gauss–Newton iteration, and the non-dominated sorting genetic algorithm II. Factory measurements were performed with Hall-probe, moving long-coil, rotating-coil, and AC response measurement systems. First-article longitudinal-gradient bending magnets achieved trajectory deviations below 40 μm and integrated-field homogeneity within specification, while production measurements enabled matched magnet grouping for series-powered operation. Measurements of the quadrupoles, RB magnets, sextupoles, and octupoles satisfied family-specific field-quality requirements or remained within lattice-accepted residual limits. Fast corrector measurements showed reproducible amplitude attenuation and phase lag from 300 Hz to 10 kHz, providing calibration data for fast-orbit-feedback operation. Beyond individual magnet prototyping, this work provides an integrated production-scale validation framework for the complete all-electromagnetic storage-ring magnet system of a diffraction-limited light source. The resulting magnetic database supports lattice modeling, magnet sorting, and storage-ring commissioning.