Research on methods for improving the absolute accuracy of circular control networks in particle accelerators

To meet the absolute positioning accuracy requirements of next-generation circular particle accelerator facilities, this paper proposes constructing a high-accuracy, straight-extended overlapping triangular backbone network for the horizontal of the HEPS storage ring control network. First, based on error propagation theory and simulation analysis, the accuracy targets for backbone network observations are defined. For measuring the long-side heights (approximately 3 m) within the large-scale obtuse triangles of the backbone network, an indirect measurement method is proposed, combining offset measurements based on stretched wires with side-length measurements of equilateral triangles formed by adding auxiliary vertices. A self-calibrating coaxial image offset meter based on telecentric optics and its supporting data processing system were independently developed. The side-length measurement scheme was designed as a high-accuracy concentric measurement solution using a μ-base rangefinder. The entire solution was deployed and implemented throughout the full circumference of the HEPS storage ring. Employing a flexible weighting strategy, results show that the backbone network achieved an observational standard deviation(SD) of 10 μm. Without compromising the smoothness of the control network, the absolute accuracy of the circular control network improved from 0.13 mm to approximately 0.07 mm, validating the effectiveness of the method.