Design and test of the motion system for HEPS storage ring horizontal collimator

Background Collimators in the storage ring of high-energy photon source(HEPS)are used to localize the beam loss,making it possible to set local radiation shields.The motion system of the collimator is used to adjust the position of the movable jaws for controlling the beam loss precisely.Moreover,dump mode of the collimator increases the risk of jaw damage from beam heat deposition.According to the requirements of motion accuracy and the severe working condition of the collimators,a new design of a two-axis motion system for the movable jaws is proposed,realizing high-precision control and extending the lifetime.Purpose The purpose of this paper is to introduce the designing scheme of the motion system for HEPS storage ring horizontal collimators,including the analyses of the key components,the structure design of the motion system and test results of the prototype.Method Temperature excursions of the movable jaw are calculated theoretically and analyzed by ANSYS,respectively.The motion accuracy of the system is measured by coordinate measuring machine.Result The temperature excursion is simulated as 1883 K while using graphite as the absorbing material at dump mode.The motion system consists of a mobile slide for aperture adjustment and a manual wedge jack for vertical adjustment.The average coupled deviation in horizontal direction of the wedge jack is 0.031 mm,while the maximum positioning deviation of the slide is 0.014 mm,both having good repeatability and being compensable.Conclusion Test results of the prototype indicate that the new design of the motion system is applicable to the horizontal collimator in HEPS storage ring.The problem of the jaw rotation in the horizontal movement is found,and the solution is given.

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°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.