Brightness is an important parameter for any synchrotron radiation source. Correcting the emittance coupling is one of the ways to increase photon beam brightness in the operational storage ring. The main source of this effect is betatron coupling, resulting from the skew quadrupolar errors. Tune split and Linear Optics from Closed Orbit (LOCO) techniques are used to measure the betatron coupling. We discuss the measurement result of betatron coupling and its correction in the Indus-2 storage ring using available four power supplies, as the knobs, driving the skew quadrupole windings located on sextupoles. The measured coupling ratio of ∼0.8% closely matches with the coupling ratio obtained from the LOCO fit model. Based on LOCO correction, the coupling ratio can be reduced to ∼0.4%, which is limited by the degrees of freedom and not by the field strengths. To achieve a smaller and controlled value of coupling, simulation studies based on the LOCO fit model and using the multi-objective differential evolution algorithm with more skew quadrupole power supplies are performed in Indus-2. With sixteen independent power supplies, the emittance ratio can be reduced to <0.04% and the brightness enhances by an order of magnitude. Besides, the optimization method used provides quantitative trade-offs between coupling related parameters such as beam tilt angle, emittance ratio, vertical emittance, and vertical beam size, and desired values can be chosen from the Pareto optimal front.

中文翻译：

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Indus-2存储环中的Betatron耦合测量与优化

亮度是任何同步辐射源的重要参数。校正发射耦合是增加操作存储环中光子束亮度的方法之一。这种效应的主要来源是电子感应加速器耦合，由偏斜四极误差引起。调谐分离和闭合轨道线性光学 (LOCO) 技术用于测量电子感应加速器耦合。我们使用可用的四个电源作为旋钮，驱动位于六极上的偏斜四极绕组，讨论了 Indus-2 存储环中的电子加速器耦合的测量结果及其校正。测得的耦合率约为0.8％，与从LOCO拟合模型获得的耦合率非常匹配。根据LOCO校正，耦合率可降低至〜0.4％，它受自由度而不是场强的限制。为了实现更小且受控的耦合值，在 Indus-2 中执行了基于 LOCO 拟合模型并使用多目标差分进化算法和更多偏斜四极杆电源的仿真研究。16个独立电源供电，发射率可降至<0.04%，亮度提升一个数量级。此外，所使用的优化方法在耦合相关参数（例如光束倾斜角，发射率，垂直发射率和垂直光束大小）之间提供了定量的权衡，可以从帕累托最优前沿中选择所需的值。在 Indus-2 中进行了基于 LOCO 拟合模型并使用多目标差分进化算法和更多偏斜四极电源的模拟研究。16个独立电源供电，发射率可降至<0.04%，亮度提升一个数量级。此外，所使用的优化方法提供了耦合相关参数（如光束倾斜角、发射率比、垂直发射率和垂直光束尺寸）之间的定量权衡，并且可以从帕累托最优前沿中选择所需的值。在 Indus-2 中进行了基于 LOCO 拟合模型并使用多目标差分进化算法和更多偏斜四极电源的模拟研究。16个独立电源供电，发射率可降至<0.04%，亮度提升一个数量级。此外，所使用的优化方法提供了耦合相关参数（如光束倾斜角、发射率比、垂直发射率和垂直光束尺寸）之间的定量权衡，并且可以从帕累托最优前沿中选择所需的值。