With the development of accelerator technology, the scale of accelerators is becoming larger, ranging from hundreds of meters to several kilometers. For stable operation of accelerators, high-precision alignment, positioning, and installation are crucial. Installing all equipment inside the tunnel poses safety risks as personnel would be in a closed environment with potential radiation exposure for prolonged periods. To address the challenges of long adjustment and maintenance periods inside the tunnel due to the installation of equipment for large-scale accelerators, most accelerator devices under construction or in research have pre-alignment assemblies. Each assembly consists of a certain number of magnets distributed on girders. The magnets in one unit are pre-aligned with high precision in the laboratory and then transported to the tunnel. Aligning the entire magnet girder can significantly improve installation efficiency inside the tunnel. To meet the pre-alignment accuracy requirement of 10 mu m in the horizontal and vertical directions for the magnet units in the high energy photon source (HEPS) storage ring, a system for high-precision pre-alignment of accelerator units using four total stations for angle observation has been designed in this paper. By employing different instrument layout configurations and incorporating reliable distance benchmarks, high-precision pre-alignment of the magnet are achieved. By arranging targets and utilizing recognition for automatic targeting, real-time point calculations during pre-alignment enhance efficiency. Subsequently, based on this system, pre-alignment simulation calculations and experimental verification of eight magnet focusing-defocusing units in the HEPS storage ring are conducted and ultimately realizing the 10 mu m transverse and vertical pre-alignment measuring error within the units. This method, based on high-precision measurements in a small-scale space, reduces the period required for personnel on-site and improves pre-alignment efficiency. It also provides a reference for pre-alignment of multiple magnet units in large accelerators such as the Southern Advanced Photon Source and Circular Electron Positron Collider.

[Background]Sextupoles 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.[Purpose]This 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.[Methods]The 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.[Results]The 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.[Conclusions]The 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.

Achieving high performance in synchrotron radiation light sources demands increased precision in fiducialization and alignment of insertion devices (IDs). Conventional sensor systems utilizing Hall probes for high-precision magnetic field measurements face limitations in determining the absolute position of the magnetic center of IDs. In this paper, the Magnetic Landmark (MLK), a novel solution based on a magnetized block structure, is designed to address this challenge. The MLK serves as an intermediary, establishing contact between the magnetic center of IDs and their externally accessible fiducials, thus enabling high-precision alignment. Through analysis of magnetic field distribution, self-calibration precision, and practical application of the MLK, the following conclusions are drawn: when the Hall probe is positioned within 0.5 mm of the magnetic field zero point inside the MLK, the measurement accuracy of the zero point for normal and skew quadrupole magnetic fields reaches 7 and 2 mu m, respectively. Additionally, the self-measurement accuracy of the MLK is 10 and 4 mu m in the transverse and vertical directions, respectively. These accuracies meet our usage requirements. The MLK demonstrates efficacy in aligning the magnetic center of High Energy Photon Source (HEPS) In-air undulators, achieving alignment accuracies of 16 mu m in the transverse direction and 11 mu m in the vertical direction, surpassing the 30 mu m accuracy stipulated in the physical design. Furthermore, the device proves applicable for measuring the magnetic center of other types of HEPS insertion devices, including Cryogenic undulators.

The Chinese high energy photon source is the fourth-generation light source that is currently under construction, with the booster being a significant component that has been completed by October 2022. In order to meet this timeline, 218 magnets requiring calibration were fitted with a rotating coil system and a three-coordinate measuring machine to optimize magnet center calibration. The rotating coil system is specially designed for magnetic center measurements. It employs a single-turn coil instead of the traditional complex compensated coil and uses a three-coordinate measuring machine imaging probe for precise positioning of the wire in space. This system has high accuracy, high speed, and high reliability. However, it is limited by the size of the three-coordinate measuring machine, meaning that larger magnets cannot be measured, thus limiting scalability. In September 2022, all of the magnets had been calibrated. This paper introduces the various aspects of coil design and examines the efficacy of employing three-coordinate measuring machine imaging for coil rotation center positioning and sag measurement, and provides a statistical analysis of calibration performance alongside mechanical calibration errors, the deviation between the magnet center and the mechanical center, and also a scatter analysis. Additionally, this paper also outlines the changes in the measuring time for each magnet, providing a reference for future magnet center calibration tasks.

High-precision pre-alignment of a magnet is a crucial step in the construction of a particle accelerator such as the Hefei Advanced Light Facility (HALF) or High Energy Photon Source (HEPS). To improve the accuracy and efficiency of pre-alignment, there are plans to build a four-station laser tracker multilateration measurement system (FLTMMS) at HALF. In the coordinate conversion and self-calibration processes of a FLTMMS, an unreasonable distribution of common points can lead to a loss of accuracy. A method for selecting common points based on uniformity in the FLTMMS is therefore proposed. In this method, the coordinate transformation space is divided according to the uniformity in different directions. The feasibility of our method is compared and analysed through coordinate conversion and self-calibration experiments. Simulations show that with the same number of common points, this method leads to higher accuracy in coordinate conversion and self-calibration. The proposed method compensates for the loss of accuracy due to aggregation of common points. Comparative analyses show a clear positive relationship between the accuracy improvement effect and the difference in uniformity. The distribution of common points will change the accuracy distribution of FLTMMS. Our approach of providing essential references for pre-aligning HALF magnets has been applied to HEPS with extensive engineering experience, to verify the practicality of this method for engineering applications. In the actual measurements, self-calibration is performed using an edge measurement network, and coordinate conversion is conducted using angle measurements. Based on actual measurements, the self-calibration accuracy is 1.7 mu m and a conversion accuracy is 14.8 mu m. The results show that under the premise of satisfying precision, the method can reduce the number of common points, thus decreasing the cost of common points construction. Our study provides instructions for pre-alignment at HALF in the future.

高能同步辐射光源(HEPS)的预准直单元数量庞大,且磁铁准直精度要求极高,为检验HEPS增强器预准直单元磁铁准直精度,需要在实验厅按照一定比例对其进行振动线磁中心验证测量.基于预研阶段已研发的振动线系统,详细介绍了振动线磁中心测量原理及扫描方法,研究了HEPS增强器两铁单元的磁中心准直精度检测方法并进行了验证实验.设计并搭建了振动线高精度重复定位夹持机构装置,研究了振动线下垂量的修正方法,并对增强器两铁单元的磁中心扫描结果进行拟合分析.实验结果表明,HEPS增强器两铁单元满足磁铁间相对位置误差优于 50 μm的预准直精度要求.

To ensure high-precision alignment of large quantities of magnets in Chinese high energy photon source, 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. 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.

High-precision pre-alignment of the magnet components is an important step in the construction and operation of the High Energy Photon Source (HEPS). In order to achieve 10 mu m pre-alignment accuracy of storage ring in transverse and vertical, four laser trackers were used for set up a four-station multilateration measurement system. A Rank-defect Free-network adjustment model was used to analysis the measurement accuracy of different arrangements of multilateration measurement system. By simulation, it shows when the four stations form a right-angled regular triangular pyramid the highest point measurement accuracy can be gotten. A multilateration measurement system formed by four laser tracker was built in the laboratory. Experiment results show that the absolute position measurement accuracy is within 7.1 mu m and the relative displacement measurement accuracy is better than 3 mu m in a 4 m x 1.2 m x 1.5 m volume, which can satisfy the real-time position feedback accuracy of the magnets in the process of ultra-high-precision pre-alignment. Then, a pre -alignment experiment for High Energy Photon Source based on this system was carried out, and finally the 10 mu m pre-alignment accuracy goal in transverse and vertical was achieved.

在高能同步辐射光源中,为了提高磁铁的准直精度,采用磁中心代替机械中心进行磁铁标定,通过振动线或旋转线等技术获得磁铁的磁中心位置,以及通过电容式位移传感器测量得到丝线的位置,从而实现磁中心与准直靶标的关联.为了实现丝线位置的高精度测量,必须对电容传感器进行精确标定,因此介绍了一种电容式位移传感器,并对其标定方法进行了研究,提出了网格化的数据采集方式以及高阶多项式拟合的数据处理方法,搭建了传感器标定平台并开发了相应的标定控制程序,实现了对传感器的自动控制、数据采集和高精度标定过程.经过分析与对比,标定后的电容传感器达到μm级的位移测量精度,为磁铁的高精度准直提供了基础.

Alignment of superconducting cavities is one of the important issues for the China Spallation Neutron Source Phase II (CSNS II) linac. In order to obtain the cavity displacement in the process of cooling down to the liquid helium temperature, a laser-based Poisson Spot Monitor (PSM) system was newly proposed and a verification system in the laboratory was built. The PSM system uses the diffraction spot formed on the CMOS camera after a beam of parallel laser passes through a spherical target to monitor the position of the measured object, where the spherical target is fixed on the monitored object. The displacement during the cooling process of the cryomodule is replaced by the movement of the high-precision two-axis motorized translation stage. A spherical target is fixed on the translation stage as the monitoring object. A beam of parallel laser passes through the spherical monitoring target to form a Poisson spot image on a CMOS camera. The coordinates of the Poisson spot center are obtained through image processing. Through experiments, the PSM system obtained a high accuracy within 5 μm, which meets the displacement monitoring requirement of the CSNS II cryomodule components. The system is fairly simple and able to be constructed without highly specialized parts and can also be used in other high-precision alignment and monitoring fields.

Background Currently, laser tracker is the primary instrument used to carry out three-dimensional position measurement in accelerator alignment. Theoretically, three-dimensional measuring data processed by three-dimensional adjustment are more rigorous, however, error accumulation is found in practice. Purpose In order to control error accumulation and further improve the measurement accuracy of accelerator alignment, this research introduces the laser alignment system into the activity of measurement and data processing. Methods A measurement scheme combining laser tracker and laser alignment system is proposed. To construct the constraint condition, the offset values from the measuring points to the laser straight-line datum were used. To carry out the three-dimensional adjustment with offset constraint, the laser tracker observations were used. Results A three-dimensional adjustment function model of laser tracker observations is given. The construction method of the constraint equation is researched, and the calculation formulas of the three-dimensional adjustment with offset constraint are derived. A 200 m linac tunnel control network is designed, using simulation measurement method, the measuring data of laser tracker and the offset values from the measuring points to the laser straight-line datum were generated. The simulated data are calculated by the method given in this paper and the result is analyzed. Conclusion Simulation result shows introducing the laser alignment system into laser tracker measurement and applying the three-dimensional adjustment with offset constraint can effectively suppress the error accumulation caused by long distance move station measurement.

围绕CSNS四极铁的中心引出标定方案进行研究,重点分析基于测磁平台获得的四极铁磁中心和旋转中心的偏差标准值;同时对每块磁铁进行两遍旋转中心和机械中心标定,比较其中心偏差标准值,分析结果表明:基于测磁平台获得的四极铁磁中心和旋转中心的偏差标准值为0.1?mm;通过两遍旋转和机械中心标定,获得的CSNS四极铁的标定重复性精度在0.03?mm之内;旋转和机械中心的偏差标准值为0.1?mm.因此同类型、同准直精度要求的设备准直在无法实施磁中心标定情况下,不能直接用机械中心代替旋转中心标定,而采用旋转中心标定,再叠加旋转和磁中心偏差进行改正的标定方案则能很好地满足当前设备准直的精度要求.

当前加速器准直主要采用激光跟踪仪进行三维空间位置测量,三维测量数据用三维平差方法计算从理论上讲更为严密,但在实践中却发现存在误差累积现象,其中在高程方向的误差累积十分明显.为了控制三维平差高程方向的误差累积,研究将大地水准面做为基准引入测量和数据处理过程之中,获得基于大地水准面的高程测量数据,用高程数据构建约束条件方程,进行附有高程约束的三维平差.以激光跟踪仪为例给出了三维平差函数模型,研究了约束方程的构建方法,推导了附有高程约束的三维平差计算公式.研究了附有高程约束的三维平差函数模型的两种应用方法,通过模拟计算展示了这两种方法对高程方向误差累积的控制效果.最后对一组实测数据采用多种平差方法进行计算对比,结果显示附有高程约束的三维平差相比无高程约束的三维平差能够更有效的控制平差中高程方向的误差累积.

以中国散裂中子源CSNS的直线加速器控制网为例,对其数据处理方法进行研究,采用平面与高程二维平差以及三维定向平差两种方式对准直控制网进行处理分析.同时,为了使准直数据处理更加简易便利,提出利用激光跟踪仪的测量软件SA实现三维定向平差的方法.通过不同软件及不同数据处理方法的对比,验证准直控制网数据处理的正确性,最终200 m长直线控制网点位精度优于0.2 mm,这为准直控制网的数据处理提供了指导.

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.