scholarly journals Direct phasing of nanocrystal diffraction

2013 ◽  
Vol 69 (6) ◽  
pp. 559-569 ◽  
Author(s):  
Veit Elser
Keyword(s):  
High Resolution ◽  
Free Electron ◽  
Free Electron Laser ◽  
Signal To Noise Ratio ◽  
Signal To Noise ◽  
High Resolution Data ◽  
X Ray ◽  
Particle Intensity ◽  
Very High ◽  
Resolution Data

Recent experiments at free-electron laser X-ray sources have been able to resolve the intensity distributions about Bragg peaks in nanocrystals of large biomolecules. Information derived from small shifts in the peak positions augment the Bragg samples of the particle intensity with samples of its gradients. Working on the assumption that the nanocrystal is entirely generated by lattice translations of a particle, an algorithm is developed that reconstructs the particle from intensities and intensity gradients. Unlike traditional direct phasing methods that require very high resolution data in order to exploit sparsity of the electron density, this method imposes no constraints on the contrast other than positivity and works well at low resolution. Successful reconstructions are demonstrated with simulatedP1 lysozyme nanocrystal data down to a signal-to-noise ratio of 2 in the intensity gradients.

scholarly journals The Effect of Intensity Fluctuations on Sequential X-ray Photon Correlation Spectroscopy at the X-ray Free Electron Laser Facilities

Crystals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1109
Author(s):  
Yue Cao ◽  
Dina Sheyfer ◽  
Zhang Jiang ◽  
Siddharth Maddali ◽  
Hoydoo You ◽  
...  
Keyword(s):  
Time Scales ◽  
Free Electron ◽  
Free Electron Laser ◽  
Photon Correlation Spectroscopy ◽  
Signal To Noise Ratio ◽  
Correlation Spectroscopy ◽  
Signal To Noise ◽  
Photon Correlation ◽  
X Ray ◽  
Intensity Fluctuations

How materials evolve at thermal equilibrium and under external excitations at small length and time scales is crucial to the understanding and control of material properties. X-ray photon correlation spectroscopy (XPCS) at X-ray free electron laser (XFEL) facilities can in principle capture dynamics of materials that are substantially faster than a millisecond. However, the analysis and interpretation of XPCS data is hindered by the strongly fluctuating X-ray intensity from XFELs. Here we examine the impact of pulse-to-pulse intensity fluctuations on sequential XPCS analysis. We show that the conventional XPCS analysis can still faithfully capture the characteristic time scales, but with substantial decrease in the signal-to-noise ratio of the g2 function and increase in the uncertainties of the extracted time constants. We also demonstrate protocols for improving the signal-to-noise ratio and reducing the uncertainties.

Effect of radiation damage and illumination variability on signal-to-noise ratio in X-ray free-electron laser single-particle imaging

2020 ◽  
Vol 76 (6) ◽  
pp. 664-676
Author(s):  
Timur E. Gureyev ◽  
Alexander Kozlov ◽  
Andrew J. Morgan ◽  
Andrew V. Martin ◽  
Harry M. Quiney
Keyword(s):  
Radiation Damage ◽  
Free Electron ◽  
Free Electron Laser ◽  
Signal To Noise Ratio ◽  
Signal To Noise ◽  
Incident Intensity ◽  
Temporal Behaviour ◽  
X Ray ◽  
Noise Ratio ◽  
Sample Reconstruction

The deterioration of both the signal-to-noise ratio and the spatial resolution in the electron-density distribution reconstructed from diffraction intensities collected at different orientations of a sample is analysed theoretically with respect to the radiation damage to the sample and the variations in the X-ray intensities illuminating different copies of the sample. The simple analytical expressions and numerical estimates obtained for models of radiation damage and incident X-ray pulses may be helpful in planning X-ray free-electron laser (XFEL) imaging experiments and in analysis of experimental data. This approach to the analysis of partially coherent X-ray imaging configurations can potentially be used for analysis of other forms of imaging where the temporal behaviour of the sample and the incident intensity during exposure may affect the inverse problem of sample reconstruction.

Investigation of the Chromosphere–Corona Interface with the Upgraded Very High Angular Resolution Ultraviolet Telescope (VAULT2.0)

2016 ◽  
Vol 05 (01) ◽  
pp. 1640003 ◽  
Author(s):  
Angelos Vourlidas ◽  
Samuel Tun Beltran ◽  
Georgios Chintzoglou ◽  
Kevin Eisenhower ◽  
Clarence Korendyke ◽  
...  
Keyword(s):  
High Resolution ◽  
Angular Resolution ◽  
Solar Spectrum ◽  
High Angular Resolution ◽  
High Resolution Data ◽  
Lyman Alpha ◽  
And Performance ◽  
White Sands ◽  
Very High ◽  
Resolution Data

Very high angular resolution ultraviolet telescope (VAULT2.0) is a Lyman-alpha (Ly[Formula: see text]; 1216[Formula: see text]Å) spectroheliograph designed to observe the upper chromospheric region of the solar atmosphere with high spatial ([Formula: see text]) and temporal (8[Formula: see text]s) resolution. Besides being the brightest line in the solar spectrum, Ly[Formula: see text] emission arises at the temperature interface between coronal and chromospheric plasmas and may, hence, hold important clues about the transfer of mass and energy to the solar corona. VAULT2.0 is an upgrade of the previously flown VAULT rocket and was launched successfully on September 30, 2014 from White Sands Missile Range (WSMR). The target was AR12172 midway toward the southwestern limb. We obtained 33 images at 8[Formula: see text]s cadence at arc second resolution due to hardware problems. The science campaign was a resounding success, with all space and ground-based instruments obtaining high-resolution data at the same location within the AR. We discuss the science rationale, instrument upgrades, and performance during the first flight and present some preliminary science results.

scholarly journals FELIX: an algorithm for indexing multiple crystallites in X-ray free-electron laser snapshot diffraction images

2017 ◽  
Vol 50 (4) ◽  
pp. 1075-1083 ◽  
Author(s):  
Kenneth R. Beyerlein ◽  
Thomas A. White ◽  
Oleksandr Yefanov ◽  
Cornelius Gati ◽  
Ivan G. Kazantsev ◽  
...  
Keyword(s):  
Free Electron Laser ◽  
Signal To Noise Ratio ◽  
X Ray Diffraction ◽  
Signal To Noise ◽  
Monoclinic Crystal ◽  
Slight Tendency ◽  
X Ray ◽  
Serial Crystallography ◽  
Diffraction Patterns ◽  
Novel Algorithm

A novel algorithm for indexing multiple crystals in snapshot X-ray diffraction images, especially suited for serial crystallography data, is presented. The algorithm, FELIX, utilizes a generalized parametrization of the Rodrigues–Frank space, in which all crystal systems can be represented without singularities. The new algorithm is shown to be capable of indexing more than ten crystals per image in simulations of cubic, tetragonal and monoclinic crystal diffraction patterns. It is also used to index an experimental serial crystallography dataset from lysozyme microcrystals. The increased number of indexed crystals is shown to result in a better signal-to-noise ratio, and fewer images are needed to achieve the same data quality as when indexing one crystal per image. The relative orientations between the multiple crystals indexed in an image show a slight tendency of the lysozme microcrystals to adhere on (\overline 110) facets.

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