Non Linear Error Analysis from Orbit Measurements in SPS and RHIC

Recently, an” action and phase” analysis of SPS orbits measurements proved to be sensitive to sextupole components intentionally activated at specific locations in the ring. In this paper we attempt to determine the strength of such sextupoles from the measured orbits and compare them with the set values. Action and phase analysis of orbit trajectories generated by RHIC models with non linearities will also be presented and compare with RHIC experiments.