Geometrical Optics Formalism to Model Contrast in Dark-Field X-ray Microscopy

Poulsen, Henning Friis; Dresselhaus-Marais, Leora E.; Carlsen, Mads; Detlefs, C.; Winther, Grethe

doi:10.48550/arxiv.2007.09475

Cited by 3 publications

(24 citation statements)

References 2 publications

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“…The relation between reciprocal space and strain components and between micromechanical models and DFXM images are discussed in detail in Ref. [26]. The vicinity of Q 0 in reciprocal space can be probed in three orthogonal directions by scanning φ, χ and a combination of φ and 2θ, respectively.…”

Section: Dfxm Geometry and Contrastmentioning

confidence: 99%

“…A formalism for forward simulation of DFXM images based on geometrical optics is described in Ref. [26]. The input is a voxelized version of a displacement gradient tensor field -which in our case is readily provided by the 1D strain wave model above.…”

Section: Geometrical Optics Formalismmentioning

confidence: 99%

“…The simulations below were performed by a slightly revised version of the code provided as Supplementary Information to Ref. [26] that also now takes into account counting noise. This is based on a model of the counts per pixel for the strain-free single crystal in the optimised "strong-beam" condition, the latter term meaning that the crystal's orientation with respect to the incident beam is centered on the Bragg condition, i.e.…”

Section: Geometrical Optics Formalismmentioning

confidence: 99%

“…The number of photons detected in each pixel is then determined by sampling from a Poisson distribution with mean given by the pixel values in raw simulated images, N simulated, raw (i, j) (as in Ref. [26]) scaled by the ratio of the estimated to the simulated strong-beam value for the diffracted photon count,…”

Section: Geometrical Optics Formalismmentioning

confidence: 99%

“…We simulate longitudinal sound wave propagation in a diamond single crystal using the thermomechanical Python modeling package udkm1Dsim [24,25]. Forward simulations of DFXM data are performed using both geometrical optics [26] and wavefront propagation optics [27] to explore the DFXM parameter-space and optimize the experimental configuration. Using a setup relevant for an experiment at the XCS instrument at the Linac Coherent Light Source (LCLS) as an example, the simulations show the propagation of a longitudinal strain wave with both a clear contrast and a good signalto-noise from a single pulse, thereby opening the door to investigating the materials science entailed in dynamic imaging of phonon propagation [28][29][30].…”

Section: Introductionmentioning

confidence: 99%

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X-ray Free Electron Laser based Dark-Field X-ray Microscopy

Holstad¹,

Ræder²,

Carlsen³

et al. 2021

Preprint

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Dark-field X-ray microscopy (DFXM) is a nondestructive full-field imaging technique providing three dimensional mapping of microstructure and local strain fields in deeply embedded crystalline elements. This is achieved by placing an objective lens in the diffracted beam, giving a magnified projection image. So far, the method has been applied with a time resolution of milliseconds to hours. In this work, we consider the feasibility of DFXM at the picosecond time scale using an X-ray free electron laser source and a pump-probe scheme. We combine thermomechanical strain wave simulations with geometrical optics and wavefront propagation optics to simulate DFXM

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Section: Dfxm Geometry and Contrastmentioning

confidence: 99%

Section: Geometrical Optics Formalismmentioning

confidence: 99%

Section: Geometrical Optics Formalismmentioning

confidence: 99%

Section: Geometrical Optics Formalismmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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X-ray Free Electron Laser based Dark-Field X-ray Microscopy

Holstad¹,

Ræder²,

Carlsen³

et al. 2021

Preprint

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In situ visualization of long-range defect interactions at the edge of melting

et al. 2021

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Connecting a bulk material’s microscopic defects to its macroscopic properties is an age-old problem in materials science. Long-range interactions between dislocations (line defects) are known to play a key role in how materials deform or melt, but we lack the tools to connect these dynamics to the macroscopic properties. We introduce time-resolved dark-field x-ray microscopy to directly visualize how dislocations move and interact over hundreds of micrometers deep inside bulk aluminum. With real-time movies, we reveal the thermally activated motion and interactions of dislocations that comprise a boundary and show how weakened binding forces destabilize the structure at 99% of the melting temperature. Connecting dynamics of the microstructure to its stability, we provide important opportunities to guide and validate multiscale models that are yet untested.

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Simultaneous Dark- and Bright-Field X-ray Microscopy at X-ray Free Electron Lasers

Howard¹,

Breckling²,

Gonzalez³

2022

Preprint

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The structures, strain fields, and defect distributions in solid materials underlie the mechanical and physical properties across numerous applications. Many modern microstructural microscopy tools characterize crystal grains, domains and defects required to map lattice distortions or deformation, but are limited to studies of the (near) surface. Generally speaking, such tools cannot probe the structural dynamics in a way that is representative of bulk behavior. Synchrotron X-ray diffraction based imaging has long mapped the deeply embedded structural elements, and with enhanced resolution, Dark Field X-ray Microscopy (DFXM) can now map those features with the requisite nm-resolution. However, these techniques still suffer from the required integration times due to limitations from the source and optics. This work extends DFXM to X-ray free electron lasers, showing how the 10 12 photons per pulse available at these sources offer structural characterization down to 100 fs resolution (orders of magnitude faster than current synchrotron images). We introduce the XFEL DFXM setup with simultaneous bright field microscopy to probe density changes within the same volume. This work presents a comprehensive guide to the multi-modal ultrafast high-resolution X-ray microscope that we constructed and tested at two XFELs, and shows initial data demonstrating two timing strategies to study associated reversible or irreversible lattice dynamics.

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Geometrical Optics Formalism to Model Contrast in Dark-Field X-ray Microscopy

Cited by 3 publications

References 2 publications

X-ray Free Electron Laser based Dark-Field X-ray Microscopy

X-ray Free Electron Laser based Dark-Field X-ray Microscopy

In situ visualization of long-range defect interactions at the edge of melting

Simultaneous Dark- and Bright-Field X-ray Microscopy at X-ray Free Electron Lasers

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