Study of the movable collimator for CEPC

Abstract

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\xa0\n $$^{\\circ }$$\n C, 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.