Coupling correction system on the SKIF light source and TbT diagnostics of linear difference resonance with swing of eigenmodes

Abstract The coupling correction system of the future SKIF light source has been optimized with the use of numerical simulation. It includes 128 BPMs (out of 224), 128 skew-quadrupoles out of 256 in MBA sections and 32 skew-quadrupoles in dispersion-free intervals. The system is complementary to the global correction and is intended to suppress simultaneously vertical dispersion and linear difference resonance. High efficiency of the EVD-based correction method has been demonstrated at various numerical examples. The possibility of determining the width of the linear difference resonance, which is necessary for such a correction, by the slope of the ellipses of normal modes is under study. The modes are resonantly swung and their elliptical shape is reproduced according to the TbT (turn-by-turn) data of the BPMs. The results of the corresponding real experiment on VEPP-4M are presented, as well as the numerical experiment on the swing of eigenmodes on the SKIF.