Purpose The beam-beam interaction can change the beam distribution,especially at the interaction point,which is a critical factor influencing the cross section of Touschek scattering.Studying the beam background with ...Purpose The beam-beam interaction can change the beam distribution,especially at the interaction point,which is a critical factor influencing the cross section of Touschek scattering.Studying the beam background with beam-beam effect will enhance our understanding of the beam background during collisions.Method A new beam dynamics code which could support strong-strong beam-beam interaction in realistic lattice tracking is used in the background simulation study.The impact of the beam-beam interaction on the beam background simulation and experiment at BEPCII is quantified both with and without beam-beam effect.Results The simulation result shows that the inclusion of beam-beam effect leads to a decrease in the beam background by approximately 20%,which is consistent with the trend of experimental observation.Since the beam dynamics tracking is more accurate with self-consistent lattice tracking and collision simulation,new tools and methodologies are expected to increase the accuracy and prediction capability of the background simulation,which would contribute to the related study in future e^(+)e^(-)colliders.展开更多
Purpose In order to update the BPM electronic in BEPCII,a high-performance digital BPM processor is designed,and the RF front-end electronic is the key part in the digital BPM processor system.Methods According to the...Purpose In order to update the BPM electronic in BEPCII,a high-performance digital BPM processor is designed,and the RF front-end electronic is the key part in the digital BPM processor system.Methods According to the BEPCII physical parameters andADCunder-sampling theorem,the low-noise and high-dynamicrange RF front-end electronic module is designed.This article will introduce filter,RF amplifier,isolation,system test,etc.Results and conclusions The experimental results showed that BPM position short-term resolution is better than 100 nm,and long-term resolution is better than 5μm.It is the first domestic BPM processor that runs stably in the storage ring accelerator for a long time.Meanwhile,the study can help us to establish a solid foundation for the next work of BPM electronics development.展开更多
Background In the linac of Beijing Electron Positron Collider II(BEPCII),the resolution of existing BPMs is several hundred microns.But the requirement of transverse position resolution of BPM for future top-up inject...Background In the linac of Beijing Electron Positron Collider II(BEPCII),the resolution of existing BPMs is several hundred microns.But the requirement of transverse position resolution of BPM for future top-up injection needs to be more precise.Purpose This paper is mainly concerned about the design and simulation of the cavity beam position monitor(CBPM)for BEPCII linac and free electron laser(FEL).The requirement of beam transverse position resolution for linac is several microns,even a few nanometers for FEL.Methods When the beam bunch goes through the CBPM,it can excite different electromagnetic field modes in resonator.In these modes,TM_(110) is the most sensitive to beam transverse position offset.The design of CBPM is aim to analyze the relationship between TM_(110) and beam transverse position by CST Studio and Ansys HFSS.Conclusion In this research,we design a pair of rectangular slots for position cavity to revise the direction of electromagnetic field.The simulation result of theoretical resolution is able to reach 15 nm@1nC with the operating frequency 2500 MHz.It is obviously that CBPM has more excellent resolution than all of operating BPM in BEPCII.Meanwhile,the research of CBPM improves the application of beam detection technology in BEPCII and accumulates technology for future design of HEPS and FEL.The mechanical design of the prototype is being fabricated.展开更多
Background The current strategy to achieve high luminosity for high energy physics experiments is to store huge currents distributed in many bunches in circular machines such as BEPCII,so the longitudinal coupled bunc...Background The current strategy to achieve high luminosity for high energy physics experiments is to store huge currents distributed in many bunches in circular machines such as BEPCII,so the longitudinal coupled bunch instabilities of the beam are inevitable.Purpose Therefore,a longitudinal feedback system is needed to suppress longitudinal oscillation.Otherwise,the beam energy spread will increase;the luminosity and the beam lifetime will decrease under a certain beam current.Methods For filter design of the feedback system,the time domain least square fitting(TDLSF)method is compared to the selective wave filter method;digital signal processing electronics based on commercial board have been developed and tested on BEPCII.Results The final result shows that the self-developed longitudinal feedback system can suppress the longitudinal beam oscillation at 750 mA beam current and meet the requirements of BEPCII;the restrain depth to the sidebands reaches to 40.8 dB.展开更多
环形加速器中,特别是强流正离子环形加速器中由于二次电子聚集而形成的电子云效应对高流强下的加速器运行会产生至关重要的影响。环形加速器中二次电子产生的主要原因在于初始电子在束流作用下获得能量,与束流真空管道内壁发生碰撞,如...环形加速器中,特别是强流正离子环形加速器中由于二次电子聚集而形成的电子云效应对高流强下的加速器运行会产生至关重要的影响。环形加速器中二次电子产生的主要原因在于初始电子在束流作用下获得能量,与束流真空管道内壁发生碰撞,如果此时真空室内壁材料的二次电子产额(Secondary Electron Yield,SEY)大于1,则会在束流管道内形成二次电子倍增而逐渐积累形成电子云。文章将结合国内近几年正离子环形加速器的设计建造参数(北京正负电子对撞机升级改造工程BEPCII、中国散裂中子源快循环同步加速器CSNS/RCS及下一代环形正负电子对撞机计划CEPC),通过二次电子产生的物理机制分析、理论计算及仿真模拟对其产生、运动、聚集及平衡过程进行研究,探索二次电子发射系数对电子云密度的影响,进而提出降低环形加速器中电子云密度的方法。展开更多
文摘Purpose The beam-beam interaction can change the beam distribution,especially at the interaction point,which is a critical factor influencing the cross section of Touschek scattering.Studying the beam background with beam-beam effect will enhance our understanding of the beam background during collisions.Method A new beam dynamics code which could support strong-strong beam-beam interaction in realistic lattice tracking is used in the background simulation study.The impact of the beam-beam interaction on the beam background simulation and experiment at BEPCII is quantified both with and without beam-beam effect.Results The simulation result shows that the inclusion of beam-beam effect leads to a decrease in the beam background by approximately 20%,which is consistent with the trend of experimental observation.Since the beam dynamics tracking is more accurate with self-consistent lattice tracking and collision simulation,new tools and methodologies are expected to increase the accuracy and prediction capability of the background simulation,which would contribute to the related study in future e^(+)e^(-)colliders.
基金the National Natural Science Foundation of China(11805221)the Union Foundation of excellent post-doctoral of China Post-Doctoral Science Foundation and Chinese Science Academy(Y71I21)。
文摘Purpose In order to update the BPM electronic in BEPCII,a high-performance digital BPM processor is designed,and the RF front-end electronic is the key part in the digital BPM processor system.Methods According to the BEPCII physical parameters andADCunder-sampling theorem,the low-noise and high-dynamicrange RF front-end electronic module is designed.This article will introduce filter,RF amplifier,isolation,system test,etc.Results and conclusions The experimental results showed that BPM position short-term resolution is better than 100 nm,and long-term resolution is better than 5μm.It is the first domestic BPM processor that runs stably in the storage ring accelerator for a long time.Meanwhile,the study can help us to establish a solid foundation for the next work of BPM electronics development.
基金the Major Projects of the Ministry of Science and Technology(Grant No.2016YFA040190301).
文摘Background In the linac of Beijing Electron Positron Collider II(BEPCII),the resolution of existing BPMs is several hundred microns.But the requirement of transverse position resolution of BPM for future top-up injection needs to be more precise.Purpose This paper is mainly concerned about the design and simulation of the cavity beam position monitor(CBPM)for BEPCII linac and free electron laser(FEL).The requirement of beam transverse position resolution for linac is several microns,even a few nanometers for FEL.Methods When the beam bunch goes through the CBPM,it can excite different electromagnetic field modes in resonator.In these modes,TM_(110) is the most sensitive to beam transverse position offset.The design of CBPM is aim to analyze the relationship between TM_(110) and beam transverse position by CST Studio and Ansys HFSS.Conclusion In this research,we design a pair of rectangular slots for position cavity to revise the direction of electromagnetic field.The simulation result of theoretical resolution is able to reach 15 nm@1nC with the operating frequency 2500 MHz.It is obviously that CBPM has more excellent resolution than all of operating BPM in BEPCII.Meanwhile,the research of CBPM improves the application of beam detection technology in BEPCII and accumulates technology for future design of HEPS and FEL.The mechanical design of the prototype is being fabricated.
文摘Background The current strategy to achieve high luminosity for high energy physics experiments is to store huge currents distributed in many bunches in circular machines such as BEPCII,so the longitudinal coupled bunch instabilities of the beam are inevitable.Purpose Therefore,a longitudinal feedback system is needed to suppress longitudinal oscillation.Otherwise,the beam energy spread will increase;the luminosity and the beam lifetime will decrease under a certain beam current.Methods For filter design of the feedback system,the time domain least square fitting(TDLSF)method is compared to the selective wave filter method;digital signal processing electronics based on commercial board have been developed and tested on BEPCII.Results The final result shows that the self-developed longitudinal feedback system can suppress the longitudinal beam oscillation at 750 mA beam current and meet the requirements of BEPCII;the restrain depth to the sidebands reaches to 40.8 dB.
文摘环形加速器中,特别是强流正离子环形加速器中由于二次电子聚集而形成的电子云效应对高流强下的加速器运行会产生至关重要的影响。环形加速器中二次电子产生的主要原因在于初始电子在束流作用下获得能量,与束流真空管道内壁发生碰撞,如果此时真空室内壁材料的二次电子产额(Secondary Electron Yield,SEY)大于1,则会在束流管道内形成二次电子倍增而逐渐积累形成电子云。文章将结合国内近几年正离子环形加速器的设计建造参数(北京正负电子对撞机升级改造工程BEPCII、中国散裂中子源快循环同步加速器CSNS/RCS及下一代环形正负电子对撞机计划CEPC),通过二次电子产生的物理机制分析、理论计算及仿真模拟对其产生、运动、聚集及平衡过程进行研究,探索二次电子发射系数对电子云密度的影响,进而提出降低环形加速器中电子云密度的方法。
