Rapid in situ X‐ray position stabilization via extremum seeking feedback. (19th February 2016)

• Record Type: Journal Article
• Authors: Zohar, S.; Venugopalan, N.; Kissick, D.; Becker, M.; Xu, S.; Makarov, O.; Stepanov, S.; Ogata, C.; Sanishvili, R.; Fischetti, R. F.
• Is Part Of: Journal of synchrotron radiation. Volume 23:Part 2(2016)
• Page Start: 443
• Page End: 447
• Publication Date: 2016-02-19
• Subjects: extremum seeking -- stabilization -- feedback -- X‐rays; Synchrotron radiation -- Periodicals; Free electron lasers -- Periodicals; 539.73505
• DOI: 10.1107/S1600577516000679
• Languages: English
• ISSNs: 0909-0495

Abstract

Abstract : A novel extremum seeking feedback method for stabilizing the X‐ray beam position at the sample is demonstrated. This method uses existing oscillations that are already present in the beam. Abstract : X‐ray beam stability is crucial for acquiring high‐quality data at synchrotron beamline facilities. When the X‐ray beam and defining apertures are of similar dimensions, small misalignments driven by position instabilities give rise to large intensity fluctuations. This problem is solved using extremum seeking feedback control (ESFC) for in situ vertical beam position stabilization. In this setup, the intensity spatial gradient required for ESFC is determined by phase comparison of intensity oscillations downstream from the sample with pre‐existing vertical beam oscillations. This approach compensates for vertical position drift from all sources with position recovery times <6 s and intensity stability through a 5 µm aperture measured at 1.5% FWHM over a period of 8 hours.