Nuclear Techniques ›› 2019, Vol. 42 ›› Issue (6): 60102-060102.doi: 10.11889/j.0253-3219.2019.hjs.42.060102


A magnet sorting method for hybrid undulators using a magnetic field camera

Maofei QIAN1,2,3,Jidong ZHANG2,Yongzhou HE2,Hongfei WANG2,Wei ZHANG2,Qiaogen ZHOU2()   

  1. 1. Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
    2. Shanghai Institute of Advanced Researches, Chinese Academy of Sciences, Shanghai 201210, China
    3. University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2019-03-20 Revised:2019-05-05 Online:2019-06-10 Published:2019-06-18
  • Contact: Qiaogen ZHOU
  • About author:QIAN Maofei, male, born in 1987, graduated from Xinjiang Astronomical Observatory, Chinese Academy of Sciences in 2011, doctoral student, focusing on the insertion devices for synchrotron light sources
  • Supported by:
    国家重点研发计划高性能磁场与短周期波荡器技术研究((No.2016YFA0402003));Supported by the National Key Research and Development Programs of China(No.2016YFA0402003)

Abstract: Background

Undulators usually need phase shimming to acquire better radiation spectrum, while phase shimming usually leads to decreased gap space and increased beam wake-field effects. Since the secondary magnetic field generated by the soft iron poles cannot be obtained directly before assembly, effective initial magnet sorting is required forthe hybrid type undulator.


This study aims to minimize the shimming distances of the hybrid undulators by sorting the magnet blocks with the help of a magnetic camera.


First of all, a new type of magnetic camera was developed, which could quickly characterize the magnetic field distribution of each magnetic block through a sensor array of 16 Hall probes that were calibrated by comparing their measured values on the same magnetic block. Then the error distribution in the magnet block was deduced from the field maps of each magnet block by least square fittings on those maps. Finally, the field signatures of these blocks were predicted by using a RADIA model with iron poles when they were installed on girder, and the magnets was sorted according to these signatures.


The variation of the half-period integral of the optimized sample undulator decreased to 53% compared with the unoptimized situation.


This method effectively shortens the shimming distances and maintains the gap space, which is essential for the construction of small period undulators.

Key words: Magnetic camera, Hybrid undulator, Magnet sorting

CLC Number: 

  • TL503