Action and phase analysis to determine sextupole errors in RHIC and the SPS

Success in the application of the action and phase analysis to find linear errors at RHIC Interaction Regions has encouraged the creation of a technique based on the action and phase analysis to find nonlinear errors. In this paper we show the first attempt to measure the sextupole components at RHIC interaction regions using the action and phase method. Experiments done by intentionally activating sextupoles in RHIC and in SPS will also be analyzed with this method. First results have given values for the sextupole errors that at least have the same order of magnitude as the values found by an alternate technique during the RHIC 2001 run.