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Theoretical analysis of the background intensity distribution in X-ray Birefringence Imaging using synchrotron bending-magnet radiation

DOI: 10.1063/1.4918925 DOI Help

Authors: John Sutter (Diamond Light Source) , Igor Dolbnya (Diamond Light Source) , Steve Collins (Diamond Light Source) , Kenneth .d.m. Harris (University of Cardiff) , Gregory Edwards-gau (Cardiff University) , Benjamin Palmer (University of Cardiff)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Applied Physics , VOL 117 (16) , PAGES 164902

State: Published (Approved)
Published: April 2015
Diamond Proposal Number(s): 8323

Open Access Open Access

Abstract: In the recently developed technique of X-ray Birefringence Imaging, molecular orientational order in anisotropic materials is studied by exploiting the birefringence of linearly polarized X-rays with energy close to an absorption edge of an element in the material. In the experimental setup, a vertically deflecting high-resolution double-crystal monochromator is used upstream from the sample to select the appropriate photon energy, and a horizontally deflecting X-ray polarization analyzer, consisting of a perfect single crystal with a Bragg reflection at Bragg angle of approximately 45°, is placed downstream from the sample to measure the resulting rotation of the X-ray polarization. However, if the experiment is performed on a synchrotron bending-magnet beamline, then the elliptical polarization of the X-rays out of the electron orbit plane affects the shape of the output beam. Also, because the monochromator introduces a correlation between vertical position and photon energy to the X-ray beam, the polarization analyzer does not select the entire beam, but instead selects a diagonal stripe, the slope of which depends on the Bragg angles of the monochromator and the polarization analyzer. In the present work, the final background intensity distribution is calculated analytically because the phase space sampling methods normally used in ray traces are too inefficient for this setup. X-ray Birefringence Imaging data measured at the Diamond Light Source beamline B16 agree well with the theory developed here.

Journal Keywords: Absorption; Anisotropy; Approximations; Birefringence; Bragg Reflection; Correlations; Electrons; Magnets; Monocrystals; Phase Space; Photons; Polarization; Rotation; Synchrotron Radiation; X Radiation

Subject Areas: Physics, Materials

Instruments: B16-Test Beamline