Yang, Y. Liang, H. Liu, Z.K. Lu, Y.S. Shen, D.S. Zhang, L. Zhang, S. Zhang, Y.S. JACoW Publishing Geneva, Switzerland 2673-5520 978-3-95450-250-9 10.18429/JACoW-MEDSI2023-THPPP023 English 313-315 monitoring vacuum synchrotron photon HOM Contribution to a conference proceedings 2024 2024-07 https://doi.org/10.18429/JACoW-MEDSI2023-THPPP023 https://jacow.org/medsi2023/papers/thppp023.pdf Vertical diffraction monochromator is a typical optical device in synchrotron radiation device. Its main requirements and characteristics are high Angle accuracy and stability. Due to the high requirements of new light sources, high precision and high stability have become a common difficulty. This paper mainly introduces the design and test of an internal crystal module of HDCM. There are two main parts: the first crystal and the second crystal. The first crystal assembly includes crystal cooling and clamping, using microchannel edge cooling and flat plate clamping schemes. The second crystal component, through the motor to the top, drives the flexible hinge, and then realizes the rotation of the crystal. At the same time, the Angle monitoring system is designed. The design scheme is verified by processing. The shape of the clamping surface of a crystal component meets the requirements of use. The motion test of the two crystal components is carried out in the atmosphere, vacuum and low temperature vacuum environment, and the results are much higher than the required parameters. And the whole stability is tested. It has high stability.