A single-turn rotating coil magnetic center calibration system designed for high energy photon source

Abstract

To ensure high-precision alignment of large quantities of magnets in Chinese High Energy Photon Source (HEPS), a high magnetic center measurement efficiency is required. To achieve this, a unique single-turn rotating coil magnetic center calibration system was designed, which simplifies the traditional multi-turn compensated coil with two sets of windings that can be connected. This design reduces measurement time significantly while increasing precision by incorporating a three-coordinate measuring machine (CMM). The study presents the system's general design, mathematical theory, and test results. Tests replacing the coil and magnets and realigning them demonstrated that the precision and measurement efficiency meet the design requirements. The displacement between the magnetic and mechanical axes was within 20 μm, indicating good performance of the well-fabricated and tested ultra-high gradient quadrupole magnet. The optimized rotating coil system design reduces the entire procedure, including magnet installation and alignment, magnetic axis measurement, and magnetic center extraction to fixed points on the magnet, to only a few hours. Several magnets participating in pre-alignment were measured, and tests and practical operation resulted in small magnetic center displacements.

Optimization of rotating coil system for magnetic center measurement and its application in high energy photon source

“…The phase-locked amplifier can accurately extract certain frequencies of signals from complex waves. For example, if the turntable rotates at 1 r s −1 , the frequencies of the low-order magnetic field and main magnetic field of a quadrupole are 1 Hz and 2 Hz, respectively, which can be accurately extracted by the phase-locked amplifier [3].…”

“…The principle of rotating coil system involves calibrating the mechanical center of the magnet and utilizing a rotating coil to measure the deviation between the magnetic center and the mechanical center, establishing the coordinate system centering at the magnetic center as the origin and introducing the coordinate of fiducials on magnets [3]. Figure 2 shows the single-turn rotating coil magnetic center calibration system developed based on this principle.…”