Observation of a tilted Gaussian beam on the 7ID beamline of the advanced photon source

An experimenter using an undulator beamline expects a Gaussian beam profile in two dimensions. Using a pinhole camera, one can measure the source size and orientation. With a camera placed far away from the source, one can measure the beam profile and estimate the source divergence. The camera can also reveal a possible tilt of the beam. In late 2005, we observed a tilt of 70 on the beam profile of the 7ID beamline, 51.5 m from the source at the Advanced Photon Source (APS). A pinhole camera measurement revealed a source tilt of only about 10. These two separate measurements implied a tilt in the divergence of the beam. The source and divergence tilts may vary for each source point of the APS. We will discuss the implication of these tilts on the performance of an insertion device beamline at the APS