Application of Vibration Wire Measurement Technology in Pre-alignment Unit of HEPS Storage Ring

The High Energy Photon Source (HEPS) storage ring, as a large-scale scientific research facility, requires precise control of its pre-alignment system, which is of utmost importance. The storage ring consists of 48 periods and 288 pre-alignment units, including 96 units each of the three-magnet units, five-magnet units, and eight-magnet units. Due to the large number of pre-alignment units and the pre-alignment accuracy requirement of 0.03 mm between magnets, the traditional single-laser tracker alignment method can no longer meet this rigorous technical demand. Therefore, the pre-alignment units of the storage ring have adopted the four-station laser tracker multiliteration measurement system, successfully achieving high-precision alignment of the pre-alignment units. To ensure that the pre-alignment accuracy of the magnetic centers of the magnets meets the design requirements, it is necessary to conduct vibration wire magnetic center verification measurements in the laboratory before the pre-alignment units are transported to the tunnel for installation. This critical measurement directly affects whether the positional accuracy between the magnets after installation can meet the physical design requirements. Given the time-consuming nature of the vibration wire magnetic center measurement process and the tight project schedule, it is not feasible to perform verification measurements on every pre-alignment unit. Therefore, the experiment selected one three-magnet unit and one five-magnet unit from the HEPS storage ring for verification measurements. In the experiment, it systematically described the vibration wire magnetic center measurement system, the vibration wire magnetic center measurement method for quadrupole magnet and its scanning process, and innovatively constructed a vibration wire sag measurement device based on a laser displacement sensor. In terms of the measurement method, an innovative vibration wire sag correction scheme was proposed, directly measuring the wire sag using a displacement sensor external reference fixture and performing polynomial fitting, comparing the results of the traditional fundamental frequency method for sag correction in the three-magnet unit with the displacement sensor measurement fitting results, confirming the reliability of the displacement sensor measurement fitting method. The experimental results show that the pre-alignment accuracy of the storage ring pre-alignment units is better than 0.015 mm, meeting the HEPS storage ring’s pre-alignment accuracy requirement of 0.03 mm. This research not only provides reliable data support for the smooth and stable operation of the high-energy photon source storage ring but also offers an effective technical means for high-precision magnetic center measurements in other similar large-scale facilities, holding significant reference value.