BEAM BASED MACHINE MODELLING FOR ORBIT CONTROL AND FEEDBACK AT DELTA

The 1.5 GeV electron storage ring Delta uses quadrupole magnets with integrated sextupoles and steerers to obtain a compact lattice. However, saturation and hysteresis effects result in nonlinear interactions between the magnet components. Therefore, optic models have so far failed to reproduce the observed optics with the required precision. We thus used beam based methods to obtain a heuristic machine model. Beam based calibration has been used to measure offsets between the signal centers of the beam position monitors and the magnetic centers of their close-by quadrupoles. Measured response matrices are used as basis for orbit feedback and local orbit bumps. These steps have significantly improved machine stability and reliability.