Beamline 4.0.2 is the first undulator beamline at the Advanced Light Source equipped with a Sasaki-type elliptically polarizing undulator (EPU). The EPU allows full control of the polarization of the x rays. Variable linear polarization from linear horizontal to linear vertical as well as 100% circular polarization are possible. The undulator in combination with a plane-grating-variable-included-angle monochromator is designed to provide high flux photon beams from 50 eV to 2000 eV, fully covering the L@sub 3,2@ edges of important magnetic transition metals (Fe, Co, Ni, ...) and also the M@sub 5,4@ edges of magnetic rare earth elements of interest (Gd, Tb, ...). We will present first experimental results that illustrate the ability of the beamline to detect small dichroism effects in dilute systems and materials which show only weak magnetic effects (<0.3%), giving us confidence in the suitability of the set up to study novel magnetic systems with high precision.