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BackgroundSextupoles are an important component of storage ring octonal unit in high energy synchrotron radiation sources. They require complex technological processes and precise center extraction. Therefore, it is necessary to find out the most reasonable calibration scheme for the mechanical center.PurposeThis study aims at the calibration scheme for the mechanical center extraction of high energy photon Ssurce (HEPS) sextupoles, and obtaining the corrected mechanical central coordinate system.MethodsThe method of directly measuring the reference plane of the sextupole was adopted for the mechanical center calibration of magnets. By rotating the conventional calibration coordinate system with a given pole seam deviation angle, the three polar seam surfaces were brought closer to the theoretical positions to decrease the main diagonal component of the sextupoles. The mechanical center calibrations were performed twice for each hexacode iron to further reduce the impact of the polar seam error.ResultsThe calibration results show that the calibration repeat accuracy is 0.005 mm for the sextupole. The standard deviation between the measured value and the design value of the pole seam spacing is 0.015 mm. Additionally, the standard deviation of the reference point before and after the rotation of the coordinate system is 0.09 mm, with a maximum rotation angle of 0.6 mrad.ConclusionsThe calibration scheme of this study can be used to improve the calibration accuracy and provide reference for the calibration of similar equipment. It ensures smooth installation of accelerator devices and is of significant importance for accelerator collimation measurements.

BackgroundCompared with 2D+1D adjustment, three dimensional adjustment has a more rigorous theoretical basis. However, when the unconstrained three dimensional adjustment is applied to the observation values processing of the accelerator alignment control network, serious error accumulation will occur and resulting in obvious distortion of the results.PurposeThis study aims to expound the ways and characteristics of three dimensional adjustment error accumulation for accelerator alignment control network.MethodsFirstly, based on the layout of accelerator alignment control network and the moving station measurement method of laser tracker, the three dimensional adjustment mathematical model was analyzed, and the least-squares collocation theory was used to clearly explain the error propagation. Secondly, the characters of laser tracker measurement accuracy, station positioning and orientation accuracy and single station measurement error propagation were studied by analyzing the laser tracker 3D coordinate measurement model, measurement point error model and simulation measurement experiments. Finally, adjustment calculation of the linac control network was verified by simulation measurement, and two error accumulation suppression methods were tested.ResultsThe source and propagation mode of error accumulation are explained theoretically, and verified by simulation calculation, so are the serious error accumulation of elevation and lateral errors in three dimensional adjustment of control network in accelerator.ConclusionsProviding high-precision point coordinate constraint for three dimensional adjustment can effectively suppress error accumulation, and providing high-precision orientation constraint for station coordinate system can also achieve the effect of suppressing error accumulation.

BackgroundThe main body of the high energy photon source (HEPS) storage ring contains 288 pre-collimating units. Due to the smaller size of the magnets in the cells, the positioning accuracy of magnets is required to be 3~5 times higher than that in previous projects.PurposeThis study aims to improve the accuracy of magnet pre-collimation and explore the high measurement accuracy and positioning accuracy of the unit magnet in the pre-collimation experiment.MethodsThe influence of multi-path laser layout schemes on the accuracy of magnetic pre-collimation was firstly simulated by combining the multichannel laser interferometry system with the magnet pre-collimation technology. Then, the simulation software MATLAB was used to optimize the layout scheme of "three high and one low" with the minimum standard deviation of the measured target point as the objective. Finally, four Leica AT960 laser trackers were employed for experimental verification of the measurement accuracy.ResultsThe results show that the standard deviation of the measured target point is less than 10 μm in the space range of 12.1 m×5.97 m×3 m, and the measurement accuracy is significantly improved compared with that of a single laser tracker.ConclusionsThe designed project meets the experimental working conditions and design requirements, it lays a foundation for subsequent beam center calibration and magnet calibration.