Development of Long Moving Coil Magnetic Field Measurement System Based on HALF Magnets

Abstract: All 120 dipole magnets in the Hefei Advanced Light Facility (HALF) storage ring are electromagnetic longitudinal gradient bend magnets with variable gaps. The precise measurement of their integral field and uniformity is crucial for ensuring beam quality. To meet the demand for efficient, high-precision measurement of these magnets in large quantities, HALF has developed a long moving coil magnetic field measurement system.The system features a uniquely designed double-layer measurement coil, enabling the simultaneous acquisition of integral field and uniformity data from two vertical planes within the magnet aperture during a single scan. It also incorporates an automated measurement function, allowing for automatic standardized magnet excitation cycles and sequential testing at pre-programmed excitation currents.Test results demonstrate that the measurement repeatability for the integral field is better than 1×10⁻⁴, and for field uniformity, better than 5×10⁻⁵, which is superior to the typical 10⁻⁴ level achieved by the Hall probe method. The successful development of this system provides a reliable technical solution for the batch testing of HALF's dipole magnets, holding substantial value for engineering applications.