BEPC储存环束流振荡频率测量

在加速器的运行和机器研究过程中,需要经常对束流振荡频率进行测量.BEPC储存环束流振荡频率测量系统包括一台频谱仪,两个条形电极装置,两个电压放大器和一个束流振荡检测器.本文介绍了经过改进的BEPC储存环束流振荡频率测量系统.     

多粒子模拟方法分析北京正负电子对撞机储存环束团长度拉伸效应

采用多粒子模拟方法,分析了北京正负电子对撞机(BEPC)储存环纵向不稳定性,给出了BEPC储存环束团长度与单束流强的关系,得出了阈值流强.模拟结果与BEPC95年4月实测结果符合较好.     

BEPCⅡ束流相关本底的蒙特卡罗模拟研究(Ⅱ)—束流-气体相互作用

介绍了用蒙特卡罗方法研究正常对撞模式下束流本底中的束流-气体相互作用的原理与效果.使用通用的模拟工具,研究了BEPCⅡ的束流-气体本底对设计中的BESⅢ的影响.结果显示,在储存环上设置挡板后,探测器的本底在允许的范围之内.模拟结果对BEPCⅡ-BESⅢ的设计建造具有指导意义.     

通过响应矩阵计算横向振荡的振幅函数和相位

 响应矩阵反映了束流位置监测器（BPM）位置处观察到的束流在校正铁磁场空间中的运行规律。根据电子储存环理论模型，采用迭代方法从实测响应矩阵计算束流横向振荡的振幅函数和相位。计算结果的精度主要受响应矩阵测量误差、BPM测量误差和校正铁电源刻度误差影响。计算响应矩阵的误差代表了迭代所采用的工作点的正确度，实际的工作点对应于计算响应矩阵的最小均方差，以此可推导实际的工作点。     

基于束流的准直的初步实验研究

束流位置探头电中心相对于邻近四极磁铁磁中心的位置偏移,可以通过基于束流的准直技术加以确定,其准直精度可以比用传统的准直方法提高一个数量级.介绍了基于束流的准直的基本原理和在BEPC储存环上的初步实验结果,以及对今后进一步开展该项实验研究的设想.     

BEPC Ⅱ工程磁铁设计与制造

北京正负电子对撞机(BEPC)改造工程是将原来的单环升级为高亮度的双环对撞机(BEPCⅡ),即在现存的BEPC隧道里增加一个新的储存环.使得BEPC Ⅱ能够提供从1.0GeV到2.1GeV能量范围的高亮度对撞束流供高能物理实验用,同时外环还要兼容2.5GeV能量250mA流强的同步辐射专用模式运行,实际上相当于有3个储存环运行.由于受到BEPC储存环隧道空间的局限,物理上的高亮度要求,以及BEPCⅡ真空盒设计采用带前室(Antechamber)结构,因此给各种磁铁设计与制造增加了相当大的难度.着重介绍BEPCⅡ储存环和对撞区中几种主要常规磁铁的设计、制造概况,同时也给出了相应的磁场测量结果.     

BEPC横向阻尼时间的测量

 利用逐束团测量系统在BEPC储存环中跟踪单个束团得到其多圈位置振荡信息，获得BEPC储存环的横向阻尼时间与束流流强、色品、八极子和束流能量的关系，并通过分析得到了BEPC储存环辐射阻尼时间为52 ms。实验结果表明：流强越高、色品越大，阻尼率也就越大；束流流强为4.7 mA时八极子强度的变化对阻尼率没有影响；束流流强为5 mA时，阻尼率随束流能量升高而减小。     

BEPCⅡ工程磁铁设计与制造

北京正负电子对撞机(BEPC)改造工程是将原来的单环升级为高亮度的双环对撞机(BEPCⅡ), 即在现存的BEPC隧道里增加一个新的储存环. 使得BEPCⅡ能够提供从1.0GeV到2.1GeV能量范围的高亮度对撞束流供高能物理实验用, 同时外环还要兼容2.5GeV能量250mA流强的同步辐射专用模式运行, 实际上相当于有3个储存环运行. 由于受到BEPC储存环隧道空间的局限, 物理上的高亮度要求, 以及BEPCⅡ真空盒设计采用带前室(Antechamber)结构, 因此给各种磁铁设计与制造增加了相当大的难度. 着重介绍BEPCⅡ储存环和对撞区中几种主要常规磁铁的设计、制造概况, 同时也给出了相应的磁场测量结果.     

电子储存环中闭合轨道和色散函数的校正

电子储存环中,由磁铁元件制造误差和安装误差导致的闭合轨道和色散函数的畸变,通常会引起一系列的负面效应,介绍了以合肥光源储存环为模型,用响应矩阵的奇值分解法对闭合轨道和色散函数进行校正的可行性研究结果.     

用条纹相机测量BEPC的束团长度

在北京正负电子对撞机(BEPC)中,正负电子束团的长度及其拉伸是束流性能重要指标之一,它直接影响到物理实验的效率,对BEPC的改进和性能进一步提高也起着关键的作用.由于用条纹相机测束团长度,具有精度高,且直观的特点,因此,近年来条纹相机在加速器束团测量领域得到了广泛的应用.本文将介绍用条纹相机测量BEPC储存环束团长度的原理、方法、系统配置、误差分析及一些典型的测量结果.     

Linear optics calibration and nonlinear optimization during the commissioning of the SSRF storage ring

Phase I commissioning of the SSRF storage ring on 3.0 GeV beam energy was started at the end of December 2007. A lot of encouraging results have been obtained so far. In this paper, calibrations of the linear optics during the commissioning are discussed, and some measured results about the nonlinearity given. Calibration procedure emphasizes correcting quadrupole magnetic coefficients with the Linear Optics from Closed Orbit (LOCO) technique. After fitting the closed orbit response matrix, the linear optics of the four test modes is substantially corrected, and the measured physical parameters agree well with the designed ones.     

Analysis and correction of linear optics errors,and operational improvements in the Indus-2 storage ring

Estimation and correction of the optics errors in an operational storage ring is always vital to achieve the design performance. To achieve this task, the most suitable and widely used technique, called linear optics from closed orbit(LOCO) is used in almost all storage ring based synchrotron radiation sources. In this technique, based on the response matrix fit, errors in the quadrupole strengths, beam position monitor(BPM) gains, orbit corrector calibration factors etc. can be obtained. For correction of the optics, suitable changes in the quadrupole strengths can be applied through the driving currents of the quadrupole power supplies to achieve the desired optics. The LOCO code has been used at the Indus-2 storage ring for the first time. The estimation of linear beam optics errors and their correction to minimize the distortion of linear beam dynamical parameters by using the installed number of quadrupole power supplies is discussed. After the optics correction, the performance of the storage ring is improved in terms of better beam injection/accumulation, reduced beam loss during energy ramping, and improvement in beam lifetime. It is also useful in controlling the leakage in the orbit bump required for machine studies or for commissioning of new beamlines.     

基于LOCO的上海光源储存环线性光学参数校正

 为了测量和校正线性光学参数,在上海光源储存环调束过程当中使用了基于响应矩阵的线性光学参数分析(LOCO)的方法。介绍了应用LOCO进行计算和校正的过程,包括：数值模拟得到束流位置探测器的测量精度对拟合结果的影响,调整四极铁电源电流强度来校正工作点和beta函数周期性的恢复。测量结果表明,在四极铁强度调整幅度在1.5%以内的情况下,储存环的束流光学参数成功地恢复到和设计值相当接近的状态,beta函数和色散函数畸变小于1%。通过束流光学参数的校正,使得在今后的工作当中可以轻松地控制储存环的工作模式。     

Progress of the Injector Linac Upgrade for the BEPCⅡ Project

BEPCⅡ—an upgrade project of Beijing Electron Positron Collider (BEPC) is a factory type of e+e- collider. It requires its injector linac to have a higher beam energy (1.89 GeV) for on-energy injection and a higher beam current (40 mA e+ beam) for a higher injection rate ( 50 mA/min). The low beam emittance (1.6π mm·mrad for e+ beam, and 0.2πmm·mrad for 300 mA e- beam) and the low beam energy spread (±0.5%) are also required to meet the storage ring acceptance. Thus the original BEPC injector linac must be upgraded to have a new electron gun with its complete tuning system, a new positron source with a flux concentrator, a new RF power system with its phasing loops and a new beam tuning system with orbit correction and optics tuning devices. These new components have been designed, fabricated, tested and will be installed in their final positions in this spring and summer, which are described in this paper.     

Linear optics calibration and nonlinear optimization during the commissioning of the SSRF storage ring

Phase I commissioning of the SSRF storage ring on 3.0 GeV beam energy was started at the end of December 2007. A lot of encouraging results have been obtained so far. In this paper, calibrations of the linear optics during the commissioning are discussed, and some measured results about the nonlinearity given. Calibration procedure emphasizes correcting quadrupole magnetic coefficients with the Linear Optics from Closed Orbit (LOCO) technique. After fitting the closed orbit response matrix, the linear optics of the four test modes is substantially corrected, and the measured physical parameters agree well with the designed ones.     

上海光源储存环线性模型校正

上海光源是我国刚刚建成的一台第三代中能同步辐射光源。为使得上海光源能够严格工作在设计状态下, 在调试过程中进行了一系列线性模型的校正, 主要包括闭轨校正、 基于束流准直（BBA）校正、 LOCO参数校正和线性耦合校正。经过反复的线性模型校正以后, 上海光源储存环的闭轨畸变均方根误差在水平和垂直两个方向可以分别控制到50和60 μm的水平, 包络函数畸变和色散函数畸变都可以控制到小于1%的状态, 工作点和束流发射度基本上校正到了设计值。线性耦合校正能够方便地将储存环的耦合度从0.02%调节到2%左右。调试结果表明, 上海光源采取的这一套线性模型校正方法, 能够有效地将上海光源的工作状态校正到设计状态, 并且为其他模式的调节奠定了基础。In the commissioning stage of Shanghai Synchrotron Radiation Facility(SSRF) storage ring, several methods were used to correct the linear optics. Beam Based Alignment(BBA) was used for BPM\|Quadrupole offsets measurement; Response matrix was used for orbit correction; LOCO was used for linear optics fitting, and quadrupoles strength were adjusted to correction the beta function; coupling was measured and corrected by skew quadrupoles. After correction, closed orbit are reduced to 50/60 μm in hortizontal and vertical plane; β beating and dispersion errors are less than 1%; betatron tune and emmittance are closed to the design value; betatron coupling also can be adjusted from 0.02% to 2%. These methods have been proved to be useful for storage ring calibrations, with the help of these methods, SSRF storage ring can be tuned to the design model and other model easily.     

Design and first commissioning of a new mode with lower emittance in the SSRF storage ring

A new mode is designed with an emittance of 2.47 nm-rad at 3.0 GeV beam energy, lower than the nominal mode of the Shanghai Synchrotron Radiation Facility (SSRF) storage ring. Details of the linear optics design and the nonlinear optimization are presented in this paper. During Phase I commissioning of the storage ring we tested the new optics mode and some expected results were obtained. After restoring the linear optics by means of the linear optics with closed orbit technique, the main parameters of the real machine agree well with the designed values and the injection efficiency and beam lifetime are acceptable.     

Measurement of optics for the SSRF storage ring in commissioning

The Shanghai Synchrotron Radiation Facility (SSRF) is a low emittance third-generation synchrotron radiation light source. Some optics parameters of the storage ring were measured when commissioning. This report presents the common methods for measuring some optics parameters of the storage ring, including the betatron tune, beta function, chromaticity, natural chromaticity and dispersion. The results and analysis of measurement for the optics parameters are given here, which are indispensable for the orbit correction of the accelerator and the nonlinear optimization.     

Orbit response matrix analysis and lattice periodicity restoration of the SSRF storage ring

In this paper, we present numerically and experimentally the linear beam-optics distortion in the SSRF storage ring and the correction of optics by using a number of quadrupole magnets installed in the storage ring. The measured orbit-response matrices were fitted to the model-response matrices to obtain the β and the dispersion functions in the storage ring. By readjusting the currents of quadrupole-magnet power supplies, we were able to successfully restore the optics parameters to values very close to the design ones, with rms deviations around 1%. This periodicity restoration is verified with the β function measurement.     

Measurement of optics for the SSRF storage ring in commissioning

The Shanghai Synchrotron Radiation Facility (SSRF) is a low emittance third-generation synchrotron radiation light source. Some optics parameters of the storage ring were measured when commissioning. This report presents the common methods for measuring some optics parameters of the storage ring, including the betatron tune, beta function, chromaticity, natural chromaticity and dispersion. The results and analysis of measurement for the optics parameters are given here, which are indispensable for the orbit correction of the accelerator and the nonlinear optimization.