Dr. Andrei Fluerasu Profile

Dr. Andrei Fluerasu

at Brookhaven National Lab

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Publications (9)

Proceedings Article | 7 June 2024 Presentation + Paper

Ghost imaging to see internal structure of a biological object with x-ray-based speckle illumination

Sanjit Karmakar, Justin Goodrich, Andrei Fluerasu, Kwangmin Yu, Cinzia Da Vià, Andrei Nomerotski, Elisha Siddiqui Matekole, Lonny Berman, Timothy Paape, Sean McSweeney

Proceedings Volume 13043, 130430J (2024) https://doi.org/10.1117/12.3021912

KEYWORDS: X-rays, Sensors, Speckle, Light sources and illumination, Biological samples, X-ray imaging, Speckle pattern, Nondestructive evaluation, Image restoration, Biological imaging

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Proceedings Article | 5 October 2023 Presentation + Paper

GPU accelerated simulations of time-dependent coherent x-ray scattering experiments

Himanshu Goel, Oleg Chubar, Lutz Wiegart, Andrei Fluerasu, Ruizi Li, An He, Max Rakitin, Meifeng Lin, Paul Moeller, Robert Nagler

Proceedings Volume 12697, 1269709 (2023) https://doi.org/10.1117/12.2677888

KEYWORDS: Simulations, X-rays, Laser scattering, Light sources, Synchrotron radiation, Scattering, Light scattering, Synchrotrons, Signal intensity

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Proceedings Article | 21 August 2020 Presentation + Paper

Analysis of hard x-ray focusing by 2D diamond CRL

Oleg Chubar, Lutz Wiegart, Sergey Antipov, Rafael Celestre, Rebecca Coles, Andrei Fluerasu, Maksim Rakitin

Proceedings Volume 11493, 114930M (2020) https://doi.org/10.1117/12.2568980

KEYWORDS: Diamond, X-rays, Beryllium, Hard x-rays, Scattering, Sensors, Light sources, X-ray optics, Lenses, Optical simulations

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Proceedings Article | 21 August 2020 Presentation + Paper

Simulations of coherent scattering experiments at storage ring synchrotron radiation sources in the hard x-ray range

Oleg Chubar, Lutz Wiegart, Andrei Fluerasu, Maksim Rakitin, James Condie, Paul Moeller, Robert Nagler

Proceedings Volume 11493, 1149310 (2020) https://doi.org/10.1117/12.2568833

KEYWORDS: Scattering, X-rays, Statistical modeling, Laser scattering, Light sources, X-ray imaging, Scanning electron microscopy, Optical simulations, Light scattering, X-ray optics

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Proceedings Article | 23 August 2017 Paper

Simulation of experiments with partially coherent x-rays using Synchrotron Radiation Workshop

Oleg Chubar, Maksim Rakitin, Yu-Chen Karen Chen-Wiegart, Andrei Fluerasu, Lutz Wiegart

Proceedings Volume 10388, 1038811 (2017) https://doi.org/10.1117/12.2274481

KEYWORDS: X-rays, Optical simulations, Synchrotron radiation, Laser scattering, Scattering, Light scattering, Wave propagation, Beam propagation method, Diagnostics, Light sources

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Proceedings Article | 23 August 2017 Paper

X-ray optical simulations supporting advanced commissioning of the coherent hard x-ray beamline at NSLS-II

L. Wiegart, M. Rakitin, A. Fluerasu, O. Chubar

Proceedings Volume 10388, 103880N (2017) https://doi.org/10.1117/12.2274403

KEYWORDS: Optical simulations, X-rays, Device simulation, X-ray optics, Hard x-rays, Synchrotron radiation, Laser scattering, Scattering, Lenses, X-ray diffraction

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Proceedings Article | 23 August 2017 Paper

Main functions, recent updates, and applications of Synchrotron Radiation Workshop code

Oleg Chubar, Maksim Rakitin, Yu-Chen Karen Chen-Wiegart, Yong Chu, Andrei Fluerasu, Dean Hidas, Lutz Wiegart

Proceedings Volume 10388, 1038805 (2017) https://doi.org/10.1117/12.2274285

KEYWORDS: X-rays, Optical simulations, Synchrotron radiation, X-ray optics, Wavefronts, Light wave propagation, Light sources, Device simulation, Wave propagation, Electron beams

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Proceedings Article | 23 September 2011 Paper

Analysis of the optical design of the NSLS-II coherent hard x-ray beamline

Andrei Fluerasu, Oleg Chubar, Konstantine Kaznatcheev, Jana Baltser, Lutz Wiegart, Kenneth Evans-Lutterodt, Mary Carlucci-Dayton, Lonny Berman

Proceedings Volume 8141, 81410J (2011) https://doi.org/10.1117/12.894129

KEYWORDS: X-rays, Visibility, Laser scattering, Scattering, Optical design, Wavefronts, Hard x-rays, Sensors, Signal to noise ratio, Wave propagation

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Ultra-low emittance third-generation synchrotron radiation sources such as the NSLS-II offer excellent opportunities for the development of experimental techniques exploiting x-ray coherence. Coherent light scattered by a heterogeneous sample produces a speckle pattern characteristic for the specific arrangement of the scatterers. This may vary over time, and the resultant intensity fluctuations can be measured and analyzed to provide information about the sample dynamics. X-ray photon correlation spectroscopy (XPCS) extends the capability of dynamic light scattering to opaque and turbid samples and extends the measurements of time evolution to nanometer length scales. As a consequence XPCS became crucial in the study of dynamics in systems including, but not being limited to, colloids, polymers, complex fluids, surfaces and interfaces, phase ordering alloys, etc. In this paper we present the conceptual optical design and the theoretical performance of the Coherent Hard X-ray (CHX) beamline at NSLS-II, dedicated to XPCS and other coherent scattering techniques. For the optical design of this beamline, there is a tradeoff between the coherence needed to distinguish individual speckles and the phase acceptance (high intensity) required to measure fast dynamics with an adequate signal-to-noise level. As XPCS is a "photon hungry" technique, the beamline optimization requires maximizing the signal-to-noise ratio of the measured intensity-intensity autocorrelation function. The degree of coherence, as measured by a two-slit (Young) experiment, is used to characterize the speckle pattern visibilities. The beamline optimization strategy consists of maximization of the on-sample intensity while keeping the degree of coherence within the 0.1-0.5 range. The resulted design deviates substantially from an ad-hoc modification of a hard x-ray beamline for XPCS measurements. The CHX beamline will permit studies of complex systems and measurements of bulk dynamics down to the microsecond time scales. In general, the 10-fold increase in brightness of the NSLS-II, compared to other sources, will allow for measurements of dynamics on time-scales that are two orders of magnitude faster than what is currently possible. We also conclude that the common approximations used in evaluating the transverse coherence length would not be sufficiently accurate for the calculation of the coherent properties of an undulator-based beamline, and a thorough beamline optimization at a low-emittance source such as the NSLS-II requires a realistic wave-front propagation analysis.

Proceedings Article | 23 September 2011 Paper

Development of partially-coherent wavefront propagation simulation methods for 3rd and 4th generation synchrotron radiation sources

Oleg Chubar, Lonny Berman, Yong Chu, Andrei Fluerasu, Steve Hulbert, Mourad Idir, Konstantine Kaznatcheev, David Shapiro, Qun Shen, Jana Baltser

Proceedings Volume 8141, 814107 (2011) https://doi.org/10.1117/12.892812

KEYWORDS: Wavefronts, Wave propagation, Optical components, Electron beams, Synchrotron radiation, Electrons, Optical simulations, X-rays, Synchrotrons, Intelligence systems

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Showing 5 of 9 publications

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