Abstract
A new correction algorithm for closed orbit distortion based on an adaptive feedforward control (AFC) has been developed. At SPring-8, two helicity-switching twin-helical undulators (THUs) had been implemented with conventional feedforward corrections. However, the validity of these corrections turned out to be expiring due to unforeseen variation in the error magnetic fields with time. The developed AFC system has been applied to the THUs dynamically updating the feedforward table without stopping the helicity switching amid user experiments. The error sources in the two THUs are successfully resolved and corrected even while the two THUs are switching simultaneously with the same repetition period. The actual operation of the new AFC system enables us to keep the orbit variations suppressed with an accuracy at the sub-micrometre level in a transparent way for light source users.
Highlights
Storage-ring-based light sources are essential platforms for photon sciences and related applications including industrial purposes
Instead of a conventional fast orbit feedback, a new closed orbit distortion (COD) correction algorithm based on adaptive feedforward control (AFC), in which the feedforward tables are dynamically updated
Assuming that the error kicks at ID23 and ID25 are very small after the modifications, the residual kicks before the modifications can be approximately regarded as the differences between the correction patterns before and after the change
Summary
Storage-ring-based light sources are essential platforms for photon sciences and related applications including industrial purposes. In the modern light sources, the pointing stability of light should be significantly smaller than the beam size This can be achieved by the closed orbit correction and other feedback controls (Rehm, 2013). Instead of a conventional fast orbit feedback, a new closed orbit distortion (COD) correction algorithm based on adaptive feedforward control (AFC), in which the feedforward tables are dynamically updated. In our AFC system, we employ newly developed fast BPMs based on MTCA. (Maesaka et al, 2019) to extract the orbit fluctuations from each ID with a high resolution and derive counter-kick patterns for updating the feedforward tables.
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