Study Of The Synchrotron Radiation Background At The CEPC

With the discovery of the Higgs particle,Chinese particle physicists,represented by the scholars from Institute of High Energy Physics,Chinese Academy of Sciences,proposed to build a Higgs particle factory-high energy Circular Electron Positron Collider(CEPC)to explore more of the Higgs particle’s properties in depth.In the normal operation of the collider,due to the high energy and powerful beam currents of CEPC,components of detectors and accelerators would be affected by the beam background within the range of 6meters upstream and downstream of the collision point,namely,the Interaction Region(IR).At the same time,some beam particles or secondary particles will be lost due to the influence of background.Therefore,the influence of beam background on detector,beam tube and collision environment cannot be ignored.This influence is mainly manifested in two aspects:one is to reduce the signal-to-noise ratio of the machine,the background signals will also trigger the detector,and the signals of the physical cases will be annihilated in the background;The other is to bring radiation damage to the relevant components,and may even reduce the life and stability of the components.Therefore,it is essential to study and analyze the background signals and take necessary measures to suppress the background level.Synchrotron radiation is one of the most important background for a large Circular Electron Positron Collider of high energy and powerful beam currents.In this paper,on the basis of the latest beam pipe modeling of CDR,considering the influence of different factors such as location,shape and materials on the suppression effect of the background,Monte Carlo simulation of synchrotron radiation photons in beam pipe were carried out and analyzed,and the harm of synchrotron radiation background and the necessity of taking measures to suppress it are demonstrated.Through the comparison of different schemes,the optimal design scheme for CEPC CDR was given,that is,a copper mask was placed 2.2 meters upstream of the center of the interaction region.The results show that the number of hits caused by SR photons in the central beryllium tube can be reduced from 8980 to 300 per bunch,and the deposition power can be improved by 1/3.The gold coating plus position optimization is the most effective way to prevent secondary particles radiation in the future,and the number of SR photons on the beryllium tube is reduced from 89 8 0 to 59 per bunch.The synchrotron radiation background in CEPC can be effectively suppressed by the optimal design scheme.