Deng, R. Deng, H.X. Gao, F. Huang, X. Lei, Z. Zhen, T.T. JACoW Publishing Geneva, Switzerland 2673-5520 978-3-95450-250-9 10.18429/JACoW-MEDSI2023-THPPP036 English 328-329 quadrupole undulator feedback radiation FEL Contribution to a conference proceedings 2024 2024-07 https://doi.org/10.18429/JACoW-MEDSI2023-THPPP036 https://jacow.org/medsi2023/papers/thppp036.pdf Quadrupole stability of undulator segment is key to the beam performance in SHINE project. Vibration stability requirement of quadrupole is not larger than 200nm displacement RMS between 1 and 100Hz, but the field test of SHINE tunnel shows that the underground vibration during the day time is greater than 200nm. In this paper, a mechanical support including marble base and active vibration reduction platform is sophisticated designed. With this support, vibration stability of the key quadrupole is expected to be improved and the performances of the quadrupole meet the demands.