Linear optics correction based on LOCO at SSRF storage ring

Linear optics from closed orbits (LOCO) has been used during the commissioning of the Shanghai Synchrotron Radiation Facility (SSRF) storage ring. The LOCO compares a model response matrix to the real machine response matrix. Using the measured response matrix of the SSRF storage ring, the gradients in all 200 quadrupole magnets were determined, and the calibration factors of steering magnets and beam position monitors (BPMs) were obtained at the same time. After adjusting the currents of quadrupole-magnet power supplies by the maximum of 1.5%, the optics parameters were restored very close to the designed values. The horizontal and vertical differences of beta function from the design values are around 10% before correction and 1% after correction.