Xiang, S.W. Deng, H.X. Deng, R. Jiang, Z.Q. Lei, Y.Y. Yang, J.Y. Zhang, W. Zhen, T.T. Zhou, S.D. JACoW Publishing Geneva, Switzerland 2673-5520 978-3-95450-250-9 10.18429/JACoW-MEDSI2023-THPPP035 English 325-327 FEL undulator SRF alignment linac Contribution to a conference proceedings 2024 2024-07 https://doi.org/10.18429/JACoW-MEDSI2023-THPPP035 https://jacow.org/medsi2023/papers/thppp035.pdf The Shanghai High repetition rate XFEL and Extreme light facility (SHINE) is under construction and aims at generating X-rays between 0.4 and 25 keV with three FEL beamlines at repetition rates of up to 1 MHz. The three undulator lines of the SHINE are referred to as the FEL-I, FEL-II, and FEL-III. Shanghai Synchrotron Radiation Facility(SSRF) will manufacture a total of 42 undulators (U26) with a period length of 26mm for FEL-I and 22 undulators (U55) with a period length of 55mm for FEL-II. Both the U26 and U55 are 4m long and use a common mechanical system. By using the specially designed double lever compensation springs can eliminate different magnetic force on the drive units. A U26 prototype has been developed and tested at SSRF. This paper describes the mechanical system design¿simulation and testing results of the U26 prototype, as well as its compatibility with U55.