Closed orbit feedback (COFB) systems at synchrotrons used for the global orbit correction rely on the pseudoinversion of the orbit response matrix (ORM). A mismatch between the model ORM used in the controller and the actual machine ORM can affect the performance of the feedback system. In this paper, the typical sources of such model mismatch such as acceleration ramp ORM variation, intensity-dependent tune shift and beta beating are considered in comprehensive simulation studies. Their effect on the performance and the stability margins are investigated for both the slow and fast regimes of a COFB system operation. The spectral radius stability condition is utilized instead of the small gain theorem to arrive at the theoretical limits of COFB stability. Comparisons with simulations for SIS18 of GSI and experiments at the cooler synchrotron (COSY) in the Forschungzentrum Jülich (FZJ) are presented.

• Received 16 March 2020
• Accepted 22 May 2020

DOI:https://doi.org/10.1103/PhysRevAccelBeams.23.072801

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Published by the American Physical Society