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@inproceedings{qian:ipac2021-wepab129,
author = {M.F. Qian and R.J. Dejus and Y. Piao and I. Vasserman and J.Z. Xu},
title = {{A New Method of Undulator Phase Tuning with Mechanical Shimming}},
booktitle = {Proc. IPAC'21},
pages = {2912--2914},
eid = {WEPAB129},
language = {english},
keywords = {undulator, MMI, radiation, operation, permanent-magnet},
venue = {Campinas, SP, Brazil},
series = {International Particle Accelerator Conference},
number = {12},
publisher = {JACoW Publishing, Geneva, Switzerland},
month = {08},
year = {2021},
issn = {2673-5490},
isbn = {978-3-95450-214-1},
doi = {10.18429/JACoW-IPAC2021-WEPAB129},
url = {https://jacow.org/ipac2021/papers/wepab129.pdf},
note = {https://doi.org/10.18429/JACoW-IPAC2021-WEPAB129},
abstract = {{We developed a new method for tuning the undulator phase errors by shimming the undulator gap profile mechanically. First, the phase errors of a device are calculated based on the initial field measurement; then the desired field strength modulation along the device length is derived from the phase errors; and finally, the gap profile is mechanically shimmed to produce the desire field strength modulation. The method has been successfully applied to the tuning of many new and reused APS Upgrade (APS-U) hybrid permanent magnet undulators. The method is especially effective for tuning the legacy undulators with large phase errors. For instance, an old 33-mm-period undulator with a 23 degree initial rms phase error largely due to radiation damage has been tuned to better than 3 degrees.}},
}