Measurement of the Orbit Response Matrix for the SIS18 Doublet Optics

This report describes the setup and results of a 2024 experiment on beam-based measurement of the Orbit Response Matrix (ORM) for the GSI Heavy Ion Synchrotron SIS18, characterising the standard doublet optics at extraction energy. The measured ORM is explicitly presented for reference. As an important outcome of this study, an effective linear machine model based on a MAD-X lattice could be established by employing the LOCO algorithm (Linear Optics from Closed Orbit), which fits free parameters in the model to match the measured ORM. The discussion compares the findings to previous measurements.