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Proceedings Paper

Optimization of a coherent soft x-ray beamline for coherent scattering experiments at NSLS-II
Author(s): David A. Shapiro; Oleg Chubar; Konstantine Kaznatcheev; Ruben Reininger; Cecilia Sanchez-Hanke; Shengyu Wang
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Paper Abstract

The coherent soft x-ray and full polarization control (CSX) beamline at the National Synchrotron Light Source - II (NSLS-II) will deliver 1013 coherent photons per second in the energy range of 0.2-2 keV with a resolving power of 2000. The source, a dual elliptically polarizing undulator (EPU), and beamline optics should be optimized to deliver the highest possible coherent flux in a 10-30 μm spot for use in coherent scattering experiments. Using the computer code Synchrotron Radiation Workshop (SRW), we simulate the photon source and focusing optics in order to investigate the conditions which provide the highest usable coherent intensity on the sample. In particular, we find that an intermediate phasing magnet is needed to correct for the relative phase between the two EPUs and that the optimum phase setting produces a spectrum in which the desired wavelength is slightly red-shifted thus requiring a larger aperture than originally anticipated. This setting is distinct from that which produces an on-axis spectrum similar to a single long undulator. Furthermore, partial coherence calculations, utilizing a multiple electron approach, indicate that a high degree of spatial coherence is still obtained at the sample location when such an aperture is used. The aperture size which maximizes the signal-to-noise ratio of a double-slit experiment is explored. This combination of high coherence and intensity is ideally suited for x-ray ptychography experiments which reconstruct the scattering density from micro-diffraction patterns. This technique is briefly reviewed and the effects on the image quality of proximity to the beamline focus are explored.

Paper Details

Date Published: 23 September 2011
PDF: 6 pages
Proc. SPIE 8141, Advances in Computational Methods for X-Ray Optics II, 81410I (23 September 2011); doi: 10.1117/12.894008
Show Author Affiliations
David A. Shapiro, Brookhaven National Lab. (United States)
Oleg Chubar, Brookhaven National Lab. (United States)
Konstantine Kaznatcheev, Brookhaven National Lab. (United States)
Ruben Reininger, Brookhaven National Lab. (United States)
Cecilia Sanchez-Hanke, Brookhaven National Lab. (United States)
Shengyu Wang, Brookhaven National Lab. (United States)

Published in SPIE Proceedings Vol. 8141:
Advances in Computational Methods for X-Ray Optics II
Manuel Sanchez del Rio; Oleg Chubar, Editor(s)

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