The beam-beam effects in a hadron collider with an unprecedented energy scale were studied.These effects are strongly related to the attainable luminosity of the collider.Long-range interactions were identified as the...The beam-beam effects in a hadron collider with an unprecedented energy scale were studied.These effects are strongly related to the attainable luminosity of the collider.Long-range interactions were identified as the major factor limiting the dynamic aperture,which is strongly dependent on the crossing angle,β*,and bunch population.Different mitigation methods of the beam-beam effects were addressed,with a focus on the compensation of long-range interactions by electric curren wires.The CEPC-SPPC project is a two-stage large circular collider,with a first-stage circular electron-positron collider(CEPC)and a second-stage super proton-proton collider(SPPC).The design of the SPPC aims to achieve a center-of-mass energy of 75 TeV and peak luminosity of approximately 1×10^(35) cm^(-2)s^(-1).We studied the beam-beam effects in the SPPC and tested the effectiveness of the mitigation methods.We found that with compensation using electric current wires,the dynamic aperture is at an acceptable level.Moreover,considering the significant emittance damping in this future proton-proton collider the beam-beam effects and compensation are more complicated and are studied using long-term tracking.It was found that with a smaller emittance,the head-on interactions with a crossing angle become more prominent in reducing the beam stability,and combined head-on and long-range compensation is needed to improve the beam quality.When the reduction in population owing to burnoff was included,it was found that the coupling between the transverse and longitudinal planes at smaller emittance is the main driving source of the instabilities.Thus,crab cavities and emittance control are also necessary than just the compensation of the long-range interactions to improve the beam stability.This study serves as an example for studying the beam-beam effects in future proton-proton colliders.展开更多
本文提出了一种低剖面锥形波束漏波天线,该天线实现了宽仰角扫描范围和较低的方位面不圆度水平。通过在平行板波导表面刻蚀一系列同心圆环漏波结构,实现了导波模式向锥形辐射波束的转换。为有效拓宽俯仰面内的扫描范围,对单元格的色散...本文提出了一种低剖面锥形波束漏波天线,该天线实现了宽仰角扫描范围和较低的方位面不圆度水平。通过在平行板波导表面刻蚀一系列同心圆环漏波结构,实现了导波模式向锥形辐射波束的转换。为有效拓宽俯仰面内的扫描范围,对单元格的色散特性进行了理论分析。利用漏波结构的等效电路模型,提取了对应的集总电路元件参数。同时,评估了不同探针配置对不圆度水平的影响,并最终设计了一种基于接地共面波导的八路等功分馈电网络。实测结果表明,该天线能够工作于30.0 GHz~37.0 GHz的频率范围,相对带宽达21%,仰角扫描范围为45°。该天线具有稳定的全向辐射特性,方位面不圆度低于1.6 d B,交叉极化水平优于-22 d B。所设计的天线可满足毫米波卫星通信和引信探测等领域的应用需求。展开更多
为了实现离子束对高精度光学表面的确定性加工,加强对加工过程中离子束去除函数的精确控制,建立细束径离子束的变去除函数补偿模型。实现对加工过程中细束径变去除函数问题的研究、分析、补偿和优化。根据实际加工中去除函数不稳定的问...为了实现离子束对高精度光学表面的确定性加工,加强对加工过程中离子束去除函数的精确控制,建立细束径离子束的变去除函数补偿模型。实现对加工过程中细束径变去除函数问题的研究、分析、补偿和优化。根据实际加工中去除函数不稳定的问题进行理论分析,结合理论推导探究影响去除函数的直接因素和间接因素,直接因素包括热积累和能量分配问题,间接因素为驻留时间和进给速度。通过动态去除函数实验验证驻留时间对加工过程中去除速率的影响,对两组不同尺寸束径的实验证明了该规律的重复性。最后,提出了基于进给速度对去除速率的影响规律给出补偿方案及加工建议。实验结果表明:通过控制驻留时间/进给速度的方式,可以有效提高细束径在高精度光学表面的加工收敛率。在亚纳米光学加工的实验验证中,在100 mm ULE平面反射镜上达到0.332 nm RMS的加工结果,满足细束径离子束在实际应用中的稳定可靠、精度高、确定性强等要求。展开更多
Beam-beam interactions cause dynamic behaviour of the charged particle beams in circular coUiders, which is directly related to their luminosity. The linear beam-beam force introduces an additional quadrupole that per...Beam-beam interactions cause dynamic behaviour of the charged particle beams in circular coUiders, which is directly related to their luminosity. The linear beam-beam force introduces an additional quadrupole that perturbs betatron motion of particles, including dynamic β, dynamic emittance and beam-beam tune-shifts; while the nonlinear force may excite resonances and cause tune-spread. With the weak-strong beam-beam mode, the linear and nonlinear effects are studied, dynamic βand dy- namic emittance as functions of tunes are analyzed, and formulas of beam-beam octupole caused tune-spread are derived, starting from beam-beam potential and equations of particle motions, and the measures to increase luminosity of BEPCII are discussed.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 11575214, 11527811, and 11805218)the Fermi Research Alliance+1 种基金LLCunder contract no. DE-AC02-07CH11359with the U.S. Department of Energy。
文摘The beam-beam effects in a hadron collider with an unprecedented energy scale were studied.These effects are strongly related to the attainable luminosity of the collider.Long-range interactions were identified as the major factor limiting the dynamic aperture,which is strongly dependent on the crossing angle,β*,and bunch population.Different mitigation methods of the beam-beam effects were addressed,with a focus on the compensation of long-range interactions by electric curren wires.The CEPC-SPPC project is a two-stage large circular collider,with a first-stage circular electron-positron collider(CEPC)and a second-stage super proton-proton collider(SPPC).The design of the SPPC aims to achieve a center-of-mass energy of 75 TeV and peak luminosity of approximately 1×10^(35) cm^(-2)s^(-1).We studied the beam-beam effects in the SPPC and tested the effectiveness of the mitigation methods.We found that with compensation using electric current wires,the dynamic aperture is at an acceptable level.Moreover,considering the significant emittance damping in this future proton-proton collider the beam-beam effects and compensation are more complicated and are studied using long-term tracking.It was found that with a smaller emittance,the head-on interactions with a crossing angle become more prominent in reducing the beam stability,and combined head-on and long-range compensation is needed to improve the beam quality.When the reduction in population owing to burnoff was included,it was found that the coupling between the transverse and longitudinal planes at smaller emittance is the main driving source of the instabilities.Thus,crab cavities and emittance control are also necessary than just the compensation of the long-range interactions to improve the beam stability.This study serves as an example for studying the beam-beam effects in future proton-proton colliders.
文摘本文提出了一种低剖面锥形波束漏波天线,该天线实现了宽仰角扫描范围和较低的方位面不圆度水平。通过在平行板波导表面刻蚀一系列同心圆环漏波结构,实现了导波模式向锥形辐射波束的转换。为有效拓宽俯仰面内的扫描范围,对单元格的色散特性进行了理论分析。利用漏波结构的等效电路模型,提取了对应的集总电路元件参数。同时,评估了不同探针配置对不圆度水平的影响,并最终设计了一种基于接地共面波导的八路等功分馈电网络。实测结果表明,该天线能够工作于30.0 GHz~37.0 GHz的频率范围,相对带宽达21%,仰角扫描范围为45°。该天线具有稳定的全向辐射特性,方位面不圆度低于1.6 d B,交叉极化水平优于-22 d B。所设计的天线可满足毫米波卫星通信和引信探测等领域的应用需求。
文摘为了实现离子束对高精度光学表面的确定性加工,加强对加工过程中离子束去除函数的精确控制,建立细束径离子束的变去除函数补偿模型。实现对加工过程中细束径变去除函数问题的研究、分析、补偿和优化。根据实际加工中去除函数不稳定的问题进行理论分析,结合理论推导探究影响去除函数的直接因素和间接因素,直接因素包括热积累和能量分配问题,间接因素为驻留时间和进给速度。通过动态去除函数实验验证驻留时间对加工过程中去除速率的影响,对两组不同尺寸束径的实验证明了该规律的重复性。最后,提出了基于进给速度对去除速率的影响规律给出补偿方案及加工建议。实验结果表明:通过控制驻留时间/进给速度的方式,可以有效提高细束径在高精度光学表面的加工收敛率。在亚纳米光学加工的实验验证中,在100 mm ULE平面反射镜上达到0.332 nm RMS的加工结果,满足细束径离子束在实际应用中的稳定可靠、精度高、确定性强等要求。
文摘Beam-beam interactions cause dynamic behaviour of the charged particle beams in circular coUiders, which is directly related to their luminosity. The linear beam-beam force introduces an additional quadrupole that perturbs betatron motion of particles, including dynamic β, dynamic emittance and beam-beam tune-shifts; while the nonlinear force may excite resonances and cause tune-spread. With the weak-strong beam-beam mode, the linear and nonlinear effects are studied, dynamic βand dy- namic emittance as functions of tunes are analyzed, and formulas of beam-beam octupole caused tune-spread are derived, starting from beam-beam potential and equations of particle motions, and the measures to increase luminosity of BEPCII are discussed.
