USE OF LOCO AT SYNCHROTRON SOLEIL
USE OF LOCO AT SYNCHROTRON SOLEIL
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LOCO 在 SYNCHROTRON SOLEIL 的使用
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发表时间：
2008
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通讯作者：
Laurent Stanislas Nadolski
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作者：
Laurent Stanislas Nadolski
SOLEIL是一个354米长的第三代光源，位于巴黎（法国）南部。在本文中，第一次尝试使用LOCO的存储环晶格紧凑性所遇到的问题一起描述。在程序中引入对四极梯度变化的约束，使程序有了很大的改进。收敛性令人满意，两个平面中的β-跳动从5% RMS降低到0.3% RMS。恢复晶格的对称性增强了储存环的性能。在最后一部分，不同的方式使用LOCO作为一个强大的诊断工具。SOLEIL是2.75 GeV的第三代同步加速器光源，自2007年1月以来为用户提供光子。储存环基于改进的Chasman-Green光学器件，其在环周围具有分布的水平色散，达到3.73 nm.rad H-发射度[1]。强大的聚焦光学系统是非常紧凑的机器的结果，在16个单元中的每个单元中容纳10个单独供电的四极磁体（Q磁体）。图1给出了光学功能的示意图。0 10 20 30 40 50 60 70 80 0 20 B et at ron fu nc tion（m）s-位置（m）0 0.2 0.4 0.6 0.8 1 D is pers ion fu nc tion（m）图1：SOLEIL存储环晶格的一个超周期的光学函数：水平（红色）和垂直（蓝色）β函数，以及水平色散函数（黑色实线）。nadolski@synchrotron-soleil.fr由于束流横向动力学对四极误差非常敏感，任何β-跳动都可能通过诱导共振激发而危及储存环的整体性能，从而导致开和关动量孔径的减少，从而导致注入效率和电子束Touschek寿命的减少[2]。尽管Q磁铁的精心构造、高质量的磁性测量以及它们在梁上完全与存储环精确对齐（低于60 μm RMS [3]），但晶格的4重对称性无法严格保留，如图2所示，其中在任何恢复晶格对称性的尝试之前都会显示H-色散函数。0 50 100 150 200 250 300 350 0.12 0.14 0.16 0.18 0.2 0.22 0.24 0.26 0.28 0.3 0.32 H-色散谱（m）s-位置（m）iter #0理想图2：SOLEIL储存环晶格的水平色散函数：对称化之前的测量（蓝色实线）和理想晶格（黑色十字）。用于恢复线性光学器件的标准工具是所谓的LOCO代码（来自闭合轨道的线性光学器件，关于方法和代码的细节，读者参考[4]和其中的参考文献）。Matlab版本的代码[5]与加速器中间层[6]和Matlab中间层[7，8]一起在SOLEIL使用。在SOLEIL，使用120个束流位置传感器（BPM）和56个转向磁铁在两个平面上测量矩阵响应通常需要25分钟。在2 Hz采集速率下测量的光束噪声在水平和垂直平面内分别为220 nm RMS和60 nm RMS。在全耦合轨道响应矩阵的拟合过程中，总共使用了896个参数（见表1）。1）。EPAC 08会议录，热那亚，意大利THPC 064 05束动力学和电磁场D 01束光学晶格，校正方案，传输
SOLEIL is a 354 m long third generation light source located South of Paris (France). In this paper, the first attempts using LOCO is described together with problems encountered due to the storage ring lattice compactness. The introduction into the code of constraints on the quadrupole gradient variations gives tremendous improvements. The convergence is satisfactory, beta-beatings are reduced from 5 to 0.3% RMS in both planes. Restoring the symmetry of the lattice enhanced the performance of the storage ring. In the last part, different ways of using LOCO as a powerful diagnostics tool are given. INTRODUCTION AND TOOLS SOLEIL is 2.75 GeV third generation synchrotron light source delivering photons to users since January 2007. The storage ring is based on a modified Chasman-Green optics with distributed horizontal dispersion all around the ring reaching a 3.73 nm.rad H-emittance [1]. The strong focusing optics is the result of the very compact machine accommodating 10 individually powered quadrupole magnets (Q-magnets) in each of the 16 cells. A sketch of the optical functions is given by figure 1. 0 10 20 30 40 50 60 70 80 0 20 B et at ro n fu nc tio n (m ) s−position (m) 0 0.2 0.4 0.6 0.8 1 D is pe rs io n fu nc tio n (m ) Figure 1: Optical functions for one super-period of the SOLEIL storage ring lattice: horizontal (red) and vertical (blue) beta functions, and horizontal dispersion function (black solid line). ∗ nadolski@synchrotron-soleil.fr Since the beam transverse dynamics is very sensitive to quadrupole errors, any beta-beating can jeopardize the global performance of the storage ring by inducing resonance excitations leading to reductions of the onand offmomentum apertures, hence of injection efficiency and ebeam Touschek life-time [2]. Despite the carefully construction of Q-magnets, the high quality of the magnetic measurements, and their precise alignment on the girders altogether into the storage ring (below 60 μm RMS [3]), the 4-fold symmetry of the lattice cannot be rigorously preserved, as shown by figure 2 where the H-dispersion function is displayed before any attempt of restoring the lattice symmetry. 0 50 100 150 200 250 300 350 0.12 0.14 0.16 0.18 0.2 0.22 0.24 0.26 0.28 0.3 0.32 H − di sp er io n (m ) s−position (m) iter #0 Ideal Figure 2: Horizontal dispersion function for the SOLEIL storage ring lattice: measurement before symmetrization (blue solid line) and ideal lattice (black crosses). A standard tool for restoring the linear optics is the socalled LOCO code (Linear Optics from Closed Orbits, for details about the method and the code, the reader is referred to [4] and references therein). The Matlab version of the code [5] is used at SOLEIL together with the Accelerator Toolbox [6] and the Matlab Middle Layer [7, 8]. Measuring a matrix response using 120 Beam Position Monitors (BPMs) and 56 steerer magnets in both planes takes typically 25 min at SOLEIL. Beam noise measured at a 2 Hz acquisition rate is 220 nm RMS and 60 nm RMS respectively in horizontal and vertical planes. A total of 896 parameters are used in the fitting procedure for the full coupled orbit response matrix (see Tab. 1). Proceedings of EPAC08, Genoa, Italy THPC064 05 Beam Dynamics and Electromagnetic Fields D01 Beam Optics Lattices, Correction Schemes, Transport