Wang, P.C. Dong, H. Liu, J.M. Liu, S.M. Ma, Y.S. Sun, X.Y. Tan, B. Wang, Y. Wang, Y.G. Zhang, L. Zhu, B.L. JACoW Publishing Geneva, Switzerland 2673-5520 978-3-95450-250-9 10.18429/JACoW-MEDSI2023-THPPP052 English 352-354 vacuum synchrotron undulator insertion-device synchrotron-radiation Contribution to a conference proceedings 2024 2024-07 https://doi.org/10.18429/JACoW-MEDSI2023-THPPP052 https://jacow.org/medsi2023/papers/thppp052.pdf The insertion devices ¿ID¿is an important guarantee for further improving the performance of the light source to meet the needs of different users. For in-air ID (undulator, wiggler, etc.), the magnetic structure is in the air, and the vacuum chamber is in the middle of the magnetic structure to ensure the normal operation of the beam. In order to increase the magnetic field strength, the magnetic gap is generally relatively small. Factors such as small setting space, high precision, and low conductance all pose challenges to the design and processing of vacuum chamber. This paper introduces the development process of the vacuum chamber prototype of the coating type ID for the China ’s first diffraction-limited light source HEPS. The simultaneous analysis and vacuum pressure distribution calculation of the ID are carried out, and the NEG coating scheme is proposed as an more economical means to obtain ultra-high vacuum. The prototype NEG coating progress is introduced.