Mechanical design of the horizontal collimator for HEPS storage ring

Background Horizontal collimators in the storage ring of high energy photon source (HEPS) are used to localize the majority of the particle loss, making it possible to set local shields. Moreover, movable jaws of the collimators are also designed as beam dumps for the machine protection, to absorb and scatter the mis-steered beam. Because of the compact lattice, each collimator should be installed between the limited space of 240 mm in the beam direction. It is necessary for the collimators to have good thermal dissipation ability to endure the synchrotron radiation and HOM load, as well as good resistance to thermal-shock from sudden beam loss simultaneously, which brings great challenges to the design. Purpose The purpose of this paper is to introduce the designing scheme of the collimators in HEPS, including the structure design and the analyses of the key components. Method Thermal and mechanical calculation has been done, based on which the jaw structure has been optimized. Besides, the modal analysis of the whole magnet-collimator-support assembly has been studied to optimize the shields structure. Result Graphite will be used as the tip for movable jaws in the collimators, which is attached to copper by vacuum brazing. The maximum temperature of the jaw during normal operation is 131 degrees C, while maximum stress of the graphite-copper weld joint is 15.6 MPa. Graphite tip can resist thermal shock caused by whole mis-steered beam. Eigen frequency of the standard assembly is acceptable for HEPS. Conclusion The results of calculations indicate that the present structure can work well for considered operating modes.