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McStas: SANS_spheres2 Component

[ Identification | Description | Input parameters | Output parameters | Links ]

The SANS_spheres2 Component


  • Author: P. Willendrup, derived from H. Frielinghaus SANS_benchmark2
  • Origin: DTU
  • Date: 16.12.2019
  • Version:(Unknown)


Sample for Small Angle Neutron Scattering - hard spheres in thin solution, mono disperse.

For the scattering simulation a high fraction of neutron paths is directed to the scattering (exact fraction is sc_aim).
The remaining paths are used for the transmitted beams. The absolute intensities are treated accordingly, and the p-parameter is set accordingly.

For the scattering probability, the integral of the scattering function between Q = 0.0001 and 1.0 AA-1 is calculated.
This is used in terms of transmisson, and of course for the scattering probability.
In this way, multiple scattering processes could be treated as well.

The typical SANS range was considered to be between 0.0001 and 1.0 AA-1.
This means that the scattered neutrons are equally distributed in this range on logarithmic Q-scales.

Example: SANS_spheres2(xwidth=0.01, yheight=0.01, zthick=0.001, model=1.0, dsdw_inc=0.02, sc_aim=0.97, sans_aim=0.95, R-150)

Input parameters

Parameters in boldface are required; the others are optional.
Name Unit Description Default
xwidth m Width of sample volume 0.01
yheight m Height of sample volume 0.01
zthick m Thickness of sample volume 0.001
dsdw_inc cm^-1 The incoherent background from the overall sample, should read ca. 1.0 for water, 0.5 for half D2O, half H2O, and ca. 0.02 for D2O 0.02
sc_aim 1 The fraction of neutron paths used to represent the scattered neutrons (including everything: incoherent and coherent). rest is transmission. 0.97
sans_aim 1 The fraction of neutron paths used to represent the scattered neutrons in the sans-range (up to 1.0AA-1). rest is incoherent with Q>1AA-1. 0.95
R AA Radius of dilute, monodisperse spheres 150
phi 1 Volume-ratio of the spheres wrt. solution 1e-3
drho cm^-2 Scattering length density 6e10
singlesp 1 Switches between multiple scattering (parameter zero 0.0) and single scattering (parameter 1.0). The sc_aim directs a fraction of paths to the first scattering process accordingly. The no. of paths for the second scattering process is derived from the real probability. Up to 10 scattering processes are considered. 1
Qmind AA^-1 Lower limit of "SANS" scattering 0.0001
Qmaxd AA^-1 Upper limit of "SANS" scattering 2.1544346900319

Output parameters

Name Unit Description Default


[ Identification | Description | Input parameters | Output parameters | Links ]

Generated automatically by McDoc, Peter Willendrup <> / Wed Jan 12 15:13:31 2022

Last Modified: Wednesday, 12-Jan-2022 16:13:31 CET
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