A numerical comparison between internal cooling and side cooling of the reflection mirror for Spatial and Spin (S2) beam-line at SSRF

Abstract To select a more appropriate cooling method for a reflection mirror of Spatial and Spin (S 2 ) beam-line at SSRF (Shanghai Synchrotron Radiation Facility), both of the internal cooling method and side cooling method were proposed and compared at various selected energy points (the most important: 50 eV, 80 eV, 100 eV and 867 eV) based on finite element analysis (FEA). For the internal cooling mode, several internal rectangular channels were drilled under the irradiation surface of mirror. For the side cooling mode, two pieces of perforated copper blocks in contact with two side surfaces of mirror were employed. Moreover, a series of side cooling modes with different tube lengths (145 mm, 200 mm, 225 mm, 248 mm and 250 mm) were analyzed. It was found that the side cooling mode with tube length of 248 mm indicated the best slope error results in all of the side cooling methods. By comparing the temperature, thermal stress distribution and slope error between the internal cooling mode and side cooling mode with tube length of 248 mm, it showed that all of the above mentioned indicators for both cooling modes were consistent with the design standards. However, the internal cooling mode presented the better results than this specific side cooling mode. In particular, by comparing some critical important influencing factors, such as the commercial cost, manufacturing process difficulty, manufacturing period and micro vibration issues, the side cooling mode with tube length of 248 mm presented better engineering operability, thus it was selected as the final cooling method for the reflection mirror of Spatial and Spin (S 2 ) beam-line at SSRF.