Chen, J. Du, X.W. Lin, M.H. Wang, Q.P. Wang, Z. JACoW Publishing Geneva, Switzerland 2673-5520 978-3-95450-250-9 10.18429/JACoW-MEDSI2023-THPPP008 English 283-286 synchrotron radiation factory optics undulator Contribution to a conference proceedings 2024 2024-07 https://doi.org/10.18429/JACoW-MEDSI2023-THPPP008 https://jacow.org/medsi2023/papers/thppp008.pdf The synchrotron facility are developing towards higher brightness, lower divergence, narrower pulse, higher stability, etc. Therefore, the requirements of the first mirror of the beamline, who bear high-heat-load, were upgraded, and the performances of the mirror will be affected easily by other factors, such as flow induced vibration, clamping force, etc. Indirect water cooling based on eInGa bath is regarded as an effective mean to solve these thorny problems in designing of the first mirror cooling. However, for the case a horizontal de-flection mirror, the unilateral cooling method is usually adopted, resulting in some changes in the structure of the mirror. In this paper, a first mirror horizontally deflect-ing in Hefei advanced light source (HALF) are taken as examples to introduce the optimization method to achieve ultra-low meridian slope error of the first hori-zontal deflection mirror. The results show that this opti-mization method provides a rapid design mean to design the cooling scheme of the horizontally deflecting mirror based on the eInGa bath.