Small x-ray beam sizes necessary for probing nanoscale phenomena require exquisite stability to prevent\ndata corruption by noise. One source of instability at synchrotron radiation x-ray beamlines is the slow\ndetuning of x-ray optics to marginal alignment where the onset of clipping increases the beamâ��s\nsusceptibility to higher frequency position oscillations. In this article, we show that a 1 �¼m amplitude\nhorizontal x-ray beam oscillation driven by power line harmonic leakage into the electron storage ring can\nbe used as perturbation for horizontal position extremum seeking feedback. Feedback performance is\ncharacterized by convergence to 1.5% away from maximum intensity at optimal alignment.
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