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Progress in HAXPES performance combining full-field k-imaging with time-of-flight recording.

ABSTRACT: An alternative approach to hard-X-ray photoelectron spectroscopy (HAXPES) has been established. The instrumental key feature is an increase of the dimensionality of the recording scheme from 2D to 3D. A high-energy momentum microscope detects electrons with initial kinetic energies up to 8?keV with a k-resolution of 0.025?Å-1, equivalent to an angular resolution of 0.034°. A special objective lens with k-space acceptance up to 25?Å-1 allows for simultaneous full-field imaging of many Brillouin zones. Combined with time-of-flight (ToF) parallel energy recording this yields maximum parallelization. Thanks to the high brilliance (1013?h??s-1 in a spot of <20?µm diameter) of beamline P22 at PETRA?III (Hamburg, Germany), the microscope set a benchmark in HAXPES recording speed, i.e. several million counts per second for core-level signals and one million for d-bands of transition metals. The concept of tomographic k-space mapping established using soft X-rays works equally well in the hard X-ray range. Sharp valence band k-patterns of Re, collected at an excitation energy of 6?keV, correspond to direct transitions to the 28th repeated Brillouin zone. Measured total energy resolutions (photon bandwidth plus ToF-resolution) are 62?meV and 180?meV FWHM at 5.977?keV for monochromator crystals Si(333) and Si(311) and 450?meV at 4.0?keV for Si(111). Hard X-ray photoelectron diffraction (hXPD) patterns with rich fine structure are recorded within minutes. The short photoelectron wavelength (10% of the interatomic distance) `amplifies' phase differences, making full-field hXPD a sensitive structural tool.

SUBMITTER: Medjanik K

PROVIDER: S-EPMC6853377 | biostudies-literature | 2019 Nov

REPOSITORIES: biostudies-literature

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Progress in HAXPES performance combining full-field k-imaging with time-of-flight recording.

Medjanik K K Babenkov S V SV Chernov S S Vasilyev D D Schönhense B B Schlueter C C Gloskovskii A A Matveyev Yu Y Drube W W Elmers H J HJ Schönhense G G

Journal of synchrotron radiation 20191101 Pt 6

An alternative approach to hard-X-ray photoelectron spectroscopy (HAXPES) has been established. The instrumental key feature is an increase of the dimensionality of the recording scheme from 2D to 3D. A high-energy momentum microscope detects electrons with initial kinetic energies up to 8 keV with a k-resolution of 0.025 Å<sup>-1</sup>, equivalent to an angular resolution of 0.034°. A special objective lens with k-space acceptance up to 25 Å<sup>-1</sup> allows for simultaneous full-field imagi ...[more]

PMID: 31721745

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Project description:Quantitative stiffness information can be a powerful aid for tumor or fibrosis diagnosis. Currently, very promising elastography approaches developed for non-contact biomedical imaging are based on transient shear-waves imaging. Transient elastography offers quantitative stiffness information by tracking the propagation of a wave front. The most common method used to compute stiffness from the acquired propagation movie is based on shear-wave time-of-flight calculations. We introduce an approach to transient shear-wave elastography with spatially coherent sources, able to yield full-field quantitative stiffness maps with reduced artifacts compared to typical artifacts observed in time-of-flight. A noise-correlation algorithm developed for passive elastography is adapted to spatially coherent narrow or any band sources. This noise-correlation-inspired (NCi) method is employed in parallel with a classic time-of-flight approach. Testing is done on simulation images, experimental validation is conducted with a digital holography setup on controlled homogeneous samples, and full-field quantitative stiffness maps are presented for heterogeneous samples and ex-vivo biological tissues. The NCi approach is first validated on simulations images. Stiffness images processed by the NCi approach on simulated inclusions display significantly less artifacts than with a time-of-flight reconstruction. The adaptability of the NCi algorithm to narrow or any band shear-wave sources was tested successfully. Experimental testing on homogeneous samples demonstrates similar values for both the time-of-flight and the NCi approach. Soft inclusions in agarose sample could be resolved using the NCi method and feasibility on ex-vivo biological tissues is presented. The presented NCi approach was successful in computing quantitative full-field stiffness maps with narrow and broadband source signals on simulation and experimental images from a digital holography setup. Results in heterogeneous media show that the NCi approach could provide stiffness maps with less artifacts than with time-of-flight, demonstrating that a NCi algorithm is a promising approach for shear-wave transient elastography with spatially coherent sources.

Dataset Information

Progress in HAXPES performance combining full-field k-imaging with time-of-flight recording.

Publications

Progress in HAXPES performance combining full-field k-imaging with time-of-flight recording.

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