Single-blockmeasurement for the cryogenic permanent magnet undulator sorting

Purpose The magnet sorting is a standard step in the undulator fabrication procedure.The shortest undulators period used in the High Energy Photon Source(HEPS)is only 12 mm.To the short period undulator,the sorting may be more important than the long-period undulator.Normally,the Helmholtz measurement is used as the input for the work.It is the averaged orthogonal magnetization of each block.In order to investigate whether the Helmholtz coil measurement is enough for the sorting,a careful study has been made.Method Firstly,a magnetic camera was used to scan the 3D surface field of a magnet.Afterward,its field integral ismeasured by the stretched wire.In the measurement,the magnetwas placed at different statuses.The results were checked to seewhether they are consistent with expected features supposing a homogeneous magnetized block.Finally,the results measured by the Helmholtz coil and the stretched wire were compared.Results The surface field scan demonstrates that the field over a magnet block is inhomogeneous.Moreover,the field integral measurement by the stretched wire also shows big difference when the different magnet sides toward thewire.The comparison between the stretched wire and the Helmholtz coil measurement shows no correlation.Conclusion The study presented in this paper reveals that the homogeneity of the magnetization is imperfect.Therefore,the Helmholtz coil data are insufficient to the short-period undulators sorting.

Study on the influence of base plate deformation on long undulators

Background Nineteen undulators of various types are being fabricated for high-energy photon source(HEPS).In order to ensure the optical performance of the undulators,the girder deformation is usually carefully optimized during the structural design stage.Purpose Optimization of magnet girder deformation is one of the key points to ensure undulator magneticfield performance.To reduce magnet girder deformation,base plate,feet and strong back should be designed carefully.In the HEPS undulator design and manufacturing stage,it is found that under special circumstances,such as after the height of the feet is adjusted,or after the undulator is lifted to other place,the base plate and girder may deform more than expected.Methods Therefore based on ANSYS simulation and experimental test results,the factors causing the deformation of the girders are carefully analyzed.Base plate and feet were optimized for different types of undulators to avoid girder deformation.Related simulation and laser tracker measurement were performed tofind out the reason in this paper.Results and conclusion Results show that the base plate of C-frame undulators will collapse and deform under the action of magnetic force.Asymmetric sagged base plate is the main reason of girder deformation.Increasing the thickness of the base plate and increasing the number of feet can both reduce that deformation.Optimization of magnet girder deformation is one of the key points to ensure undulator magneticfield performance.To reduce magnet girder deformation,base plate,feet and strong back should be designed carefully.