Beam-Based Calibration of the Linear Optics Model of ELSA

The Electron Stretcher Accelerator (ELSA) of Bonn University is used to provide an external electron beam of high duty factor in the energy range from 0.5–3.5 GeV for fixed target experiments. In the near future polarized electron beams will be accelerated up to the highest energies. In order to avoid depolarization of the beam by imperfection and intrinsic resonances the control of the closed orbit and the symmetry of the ring lattice has to be improved. For calibration of the optics model of ELSA the orbit response matrix has been measured and fitted with help of the program CALIF. The strengths of the two quadrupole families and the relative scaling factors for the beam position monitors and corrector magnets have been determined this way. The results of the fits and a comparison with measurements of the optical functions of ELSA will be presented.