Study of themovable collimator for CEPC

Background Movable collimators for the circular electron positron collider(CEPC)are required to cut off spent electrons/positrons just near the beam orbit and reduce the background of the detector.Due to the extremely high energy and luminosity of CEPC,a lot of challenges are brought to the collimators,including the huge synchrotron radiation power,the high-energy beam impact,and low impedance requirement.Purpose The purpose of this paper is to design a movable collimator suitable for CEPC and calculate its performance.Method Based on geant4 simulations and finite element method(FEM)analyses,a lot of studies were done:synchrotron radiation power,thermal and mechanical calculation,beam impact,and impedance,respectively.Result The maximum temperature of the design during normal operation is 143℃,and the loss factor is only 0.021 V/pC ignoring the shielding of clearance.Conclusions The conceptual design of collimator was completed,and the calculations show the design can work well under normal operating condition.