Interpretation of dark-field contrast and particle-size selectivity in grating interferometers
In grating-based x-ray phase sensitive imaging, dark-field contrast refers to the extinction of the interference fringes due to small-angle scattering. For configurations where the sample is placed before the beamsplitter grating, the dark-field contrast has been quantified with theoretical wave propagation models. Yet when the grating is placed before the sample, the dark-field contrast has only been modeled in the geometric optics regime. Here we attempt to quantify the dark-field effect in the grating-before-sample geometry with first-principle wave calculations and understand the associated particle-size selectivity. We obtain an expression for the dark-field effect in terms of the sample material's complex refractive index, which can be verified experimentally without fitting parameters. A dark-field computed tomography experiment shows that the particle-size selectivity can be used to differentiate materials of identical x-ray absorption.
- OSTI ID:
- 22036686
- Journal Information:
- Applied Optics, Journal Name: Applied Optics Journal Issue: 22 Vol. 50; ISSN 0003-6935; ISSN APOPAI
- Country of Publication:
- United States
- Language:
- English
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