Analysis Of Beam Background At Electron-positron Colliders In The Tau-charm Energy Region

Particle collider is one of the most important tools to research of particle physics nowadays,it can be classified into high energy frontier collider and high luminosity frontier collider.The upgraded Beijing Electron-Positron Collider(BEPCII)is a high luminosity frontier collider working at the tau-charm energy region.In the past decades,BEPCII and its detector Beijing spectrometer(BESⅢ)has made a series of achievements.As time going on,the aging problem of BEPCII and BESⅢ becomes more and more serious.Meanwhile,the physics researches in this field are asking for more data in this energy region.People are prospecting for next generation of collider working in the tau-charm energy region:the Super Tau-Charm Facility(STCF).To reach a higher luminosity,STCF has higher beam current and narrower beam size than BEPCII,the consequent higher beam background brings severe challenges to the design of accelerator and detector.When beam particles are tracking in the accelerator,they may deviate from the orbit by Touschek effect,beam-gas scattering and so on.Then they may go directly or generate secondary particles into the detector and cause background in the detector,which is called beam background.High beam background in collider is extremely dangerous,its heating can cause quench of the super conducting magnet,the TID and NIEL from it can cause damage and reduce lifetime of the detector,the high count rate can make problem on the design of trigger and readout system.So the estimation and inhibition of beam background are essential for a collider design.In this thesis,we introduce simulation programs and corresponding simulation results to research beam background on STCF.The beam related background is generated by sampling with theoretical formula and the luminosity related background is generated with available simulation tools.Particle tracking in the storage ring is simulated with SAD program developed by KEK.The interaction between particles and MDI materials and the detector response are simulated with Geant4.In consideration of complex mechanism of background,we did twice background experiments on BEPCII to verify simulation,in which the background components are separated by changing the beam parameters.We also did collimator experiment to study the relevance of aperture and background.The difference of simulation and experiment has been reduced from 4 order of magnitude to 1 or 2 after modifying the simulation.The thesis also search and discuss the possible reasons to cause the difference.On base of designing the MDI geometry,the thesis estimate the background level of STCF with the updated simulation.The collimators are designed and optimized to reduce the background.The quantitative irradiation metering and counting rate are carried out as final results,which are crucial reference of the detector design.