Characterization of the X‐ray coherence properties of an undulator beamline at the Advanced Photon Source. (13th June 2018)

• Record Type: Journal Article
• Authors: Ju, Guangxu; Highland, Matthew J.; Thompson, Carol; Eastman, Jeffrey A.; Fuoss, Paul H.; Zhou, Hua; Dejus, Roger; Stephenson, G. Brian
• Is Part Of: Journal of synchrotron radiation. Volume 25:Part 4(2018)
• Page Start: 1036
• Page End: 1047
• Publication Date: 2018-06-13
• Subjects: coherence -- divergence -- brightness; Synchrotron radiation -- Periodicals; Free electron lasers -- Periodicals; 539.73505
• DOI: 10.1107/S1600577518006501
• Languages: English
• ISSNs: 0909-0495

Abstract

Abstract : Methods are described to measure divergence by imaging the apparent source size using either slits to form a pinhole camera or a compound refractive lens. The values of brightness and coherent flux obtained are compared with those calculated for the undulator source, to evaluate the effects of beamline optics. Abstract : In anticipation of the increased use of coherent X‐ray methods and the need to upgrade beamlines to match improved source quality, here the coherence properties of the X‐rays delivered by beamline 12ID‐D at the Advanced Photon Source have been characterized. The measured X‐ray divergence, beam size, brightness and coherent flux at energies up to 26 keV are compared with the calculated values from the undulator source, and the effects of beamline optics such as a mirror, monochromator and compound refractive lenses are evaluated. Diffraction patterns from slits as a function of slit width are analyzed using wave propagation theory to obtain the beam divergence and thus coherence length. Imaging of the source using a compound refractive lens was found to be the most accurate method for determining the vertical divergence. While the brightness and coherent flux obtained without a monochromator (`pink beam') agree well with those calculated for the source, those measured with the monochromator were a factor of three to six lower than the source, primarily because of vertical divergence introduced by the monochromator. The methods described herein should be widely applicable for measuring the X‐ray coherence properties of synchrotron beamlines.