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。     

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.     

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.     

工作点反馈系统对同步辐射光源运行稳定性的提升

上海同步辐射装置（SSRF）储存环上目前已经安装了十台插入元件（IDs）。在用户时间,插入元件的间隙被反复地调整以进行科学实验。虽然使用了插入件前馈系统,但依然存在扰动束流光学的残余四极场,它会导致束流横向振荡工作点的变化,进而影响机器的性能和同步辐射光亮度的稳定。为此,我们研发了一个工作点反馈系统来解决这个问题,并且已经在上海光源储存环上投入了运行,在两周左右的运行周期内,工作点的稳定度达到了±0.001。这个反馈系统还有另一个重要功能,即可以根据监控反馈系统校正电流的变化趋势来判断二极磁铁电源和四极磁铁电源是否存在慢漂问题。为了验证这个工作点反馈的可行性,我们对使用反馈前后几周的束流参数进行了比较,包括储存环注入效率、束流寿命、水平方向束斑尺寸以及β函数的变化情况（beta-beatings）。     

工作点反馈系统对同步辐射光源运行稳定性的提升（英文）

上海同步辐射装置(SSRF)储存环上目前已经安装了十台插入元件(IDs)。在用户时间,插入元件的间隙被反复地调整以进行科学实验。虽然使用了插入件前馈系统,但依然存在扰动束流光学的残余四极场,它会导致束流横向振荡工作点的变化,进而影响机器的性能和同步辐射光亮度的稳定。为此,我们研发了一个工作点反馈系统来解决这个问题,并且已经在上海光源储存环上投入了运行,在两周左右的运行周期内,工作点的稳定度达到了±0.001。这个反馈系统还有另一个重要功能,即可以根据监控反馈系统校正电流的变化趋势来判断二极磁铁电源和四极磁铁电源是否存在慢漂问题。为了验证这个工作点反馈的可行性,我们对使用反馈前后几周的束流参数进行了比较,包括储存环注入效率、束流寿命、水平方向束斑尺寸以及β函数的变化情况(beta-beatings)。     

合肥光源储存环聚焦模型标定

 描述了利用轨道响应矩阵拟合技术标定合肥光源储存环聚焦模型的过程及实验结果。通过响应矩阵分析,得到了合肥光源储存环弯铁边缘聚焦强度约为0.1 mrad/A,场积分为0.62~0.63,考虑了四极铁聚焦强度的修正系数的影响,发现了原四极铁磁测数据中较大的系统偏差,分析结果和备用磁铁的磁场测量数据吻合良好。在此基础上建立的合肥光源储存环理论模型可以准确地描述实际储存环线性光学特性。     

响应矩阵分析方法在BEPC储存环上的应用

由于储存环中各种元件误差的存在, 机器的实际运行模式与设计模式有一定的偏差. 目前广泛开展的响应矩阵方法研究, 可以分析出磁铁元件以及束流位置测量元件的误差, 使束流基本参数得到校正. 介绍了用响应矩阵分析方法, 在BEPC储存环上进行的局部轨道校正的实验研究, 以及BEPC储存环束流参数校正的模拟研究.     

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,     

Preliminary application of turn-by-turn data analysis to the SSRF storage ring

There is growing interest in utilizing the beam position monitor turn-by-turn (TBT) data to debug accelerators. TBT data can be used to determine the linear optics, coupled optics and nonlinear behaviors of the storage ring lattice. This is not only a useful complement to other methods of determining the linear optics such as LOCO, but also provides a possibility to uncover more hidden phenomena. In this paper, a preliminary application of a β function measurement to the SSRF storage ring is presented.     

Beam based alignment of the SSRF storage ring

There are 140 beam position monitors (BPMs) in the Shanghai Synchrotron Radiation Facility (SSRF) storage ring used for measuring the closed orbit. As the BPM pickup electrodes are assembled directly on the vacuum chamber, it is important to calibrate the electrical center offset of the BPM to an adjacent quadrupole magnetic center. A beam based alignment (BBA) method which varies individual quadrupole magnet strength and observes its effects on the orbit is used to measure the BPM offsets in both the horizontal and vertical planes. It is a completely automated technique with various data processing methods. There are several parameters such as the strength change of the correctors and the quadrupoles which should be chosen carefully in real measurement. After several rounds of BBA measurement and closed orbit correction, these offsets are set to an accuracy better than 10 μm. In this paper we present the method of beam based calibration of BPMs, the experimental results of the SSRF storage ring, and the error analysis.     

A GUI tool for beta function measurement using MATLAB

The beta function measurement is used to detect the shift in the betatron tune as the strength of an individual quadrupole magnet is varied. A GUI (graphic user interface) tool for the beta function measurement is developed using the MATLAB program language in the Linux environment, which facilitates the commissioning of the Shanghai Synchrotron Radiation Facility (SSRF) storage ring. In this paper, we describe the design of the application and give some measuring results and discussions about the definition of the measurement. The program has been optimized to solve some restrictions of the AT tracking code. After the correction with LOCO (linear optics from closed orbits), the horizontal and the vertical root mean square values (rms values) can be reduced to 0.12 and 0.10.     

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.     

BEPCⅡ LINAC束流光学匹配及轨道校正计算研究

 北京正负电子对撞机直线注入器(BEPCⅡ LINAC)的升级改进要求建立束流光学匹配计算和轨道校正系统，为此对束流光学匹配计算和轨道校正计算的方法进行了研究，并采用VC++语言编写了相应的程序，利用最小二乘法原理进行了束流光学匹配计算，模拟了束流轨道校正，取得了较为理想的结果。     

BEPCⅡ LINAC束流光学匹配及轨道校正计算研究

北京正负电子对撞机直线注入器(BEPCⅡ LINAC)的升级改进要求建立束流光学匹配计算和轨道校正系统,为此对束流光学匹配计算和轨道校正计算的方法进行了研究,并采用VC++语言编写了相应的程序,利用最小二乘法原理进行了束流光学匹配计算,模拟了束流轨道校正,取得了较为理想的结果。     

合肥光源基于束流准直系统的控制软件设计

束流位置监测器（BPM）和与其相邻的四极铁之间的电偏移对于电子储存环轨道校正十分重要。改变四极铁的强度,并通过测量轨道变化就能够计算出该四极铁的磁中心相对于相邻的BPM的电中心之间的偏差。基于NSRL储存环的BBA硬件系统和EPICS控制系统,采用Labview平台开发出了BBA测量的软件控制程序。由计算机控制四极铁的强度,连续测量后拟合得到四极铁的磁中心与相邻BPM的相对偏差,测量精度可以达到100 μm。     

合肥光源基于束流准直系统的控制软件设计

束流位置监测器(BPM)和与其相邻的四极铁之间的电偏移对于电子储存环轨道校正十分重 要。改变四极铁的强度,并通过测量轨道变化就能够计算出该四极铁的磁中心相对于相邻的BPM的电中心 之间的偏差。基于NSRL储存环的BBA硬件系统和EPICS控制系统,采用Labview平台开发出了BBA测量 的软件控制程序。由计算机控制四极铁的强度,连续测量后拟合得到四极铁的磁中心与相邻BPM的相对偏 差,测量精度可以达到100μm。     

Preliminary Study on Measurement of Magnetic Center of Quadrupoles Using Quadrupole Shunt for Hefei Storage Ring

The theoretical analysis of the DC K-modulation of quadrupole for the beam-based alignment method is presented. It is shown that the shift of the orbit,when the focussing strength of one quadrupole magnet is changed,can be described by the perturbed or unperturbed linear lattice parameters. The beam-based alignment system is constructed using DC K-modulation of quadrupole. In order to use the beam-based alignment method one must be able to individually adjust the strength of the quadrupole magnet. So,a switchable shunt resistor is installed on quadrupole to bypass 1%-2.5% magnet current and some solid-state relays are used to switch the shunt resistor in this beam-based alignment system. To improve the measurement accuracy,two methods are used. First method is that beam positions in measured quadrupole magnet are moved by local bump of beam closed orbit using the corrector magnets. Second method is that the root-mean-square of difference in closed orbit is fitted by a parabola function. The system can be not only used to position the beam in the magnetic center of quadrupoles,but also to measure the β function in quadrupole magnets. Some preliminary measurement results are given for Hefei 800MeV electron storage ring. These experimental results show that this system is valid to position the beam to the center of the quadrupole magnets and measure the β function at Hefei Light Source.     

基于MATLAB的合肥光源储存环束流轨道校正系统

闭轨畸变对合肥同步光源的束流质量产生负面影响,因此必须对闭轨畸变进行校正。本文介绍了基于MATLAB的合肥光源储存环束流轨道校正系统的工作原理、开发过程及测试结果。该系统由束流轨道测量系统、校正铁系统和控制系统组成,基于MATLAB开发的束流轨道校正程序运行于操作员界面工作站上。首先对获取的束流轨道数据进行分析和计算,然后通过控制系统改变校正铁电源的电流以改变校正铁磁场强度,从而实现轨道校正。测试结果表明：束流轨道的最大畸变由校正前的4.468 mm下降到校正后的0.299 mm;标准方差（SDEV）由校正前的2.986 mm下降到校正后的0.087 mm。该系统达到了设计目标。     

基于MATLAB的合肥光源储存环束流轨道校正系统

 闭轨畸变对合肥同步光源的束流质量产生负面影响,因此必须对闭轨畸变进行校正。本文介绍了基于MATLAB的合肥光源储存环束流轨道校正系统的工作原理、开发过程及测试结果。该系统由束流轨道测量系统、校正铁系统和控制系统组成,基于MATLAB开发的束流轨道校正程序运行于操作员界面工作站上。首先对获取的束流轨道数据进行分析和计算,然后通过控制系统改变校正铁电源的电流以改变校正铁磁场强度,从而实现轨道校正。测试结果表明：束流轨道的最大畸变由校正前的4.468 mm下降到校正后的0.299 mm;标准方差（SDEV）由校正前的2.986 mm下降到校正后的0.087 mm。该系统达到了设计目标。