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14.71 The GISANS_sample McStas Component
Sample for GISANS
Identification
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Author: H. Frielinghaus
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Origin: FZJ
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Date: March 2023
Description
The idea of this sample goes back to the real sample studied in the publication https://doi.org/10.1063/1.4723634 This is a sandwich of a sapphire and silicon slab through which the neutrons impinge and the sample in between where the scattering emerges from. The sample consist of spherical polystyrene colloids in heavy water that form aligned crystallites at the solid-liquid interface, while in the middle of the volume the crytallites are orientationally averaged in the polar angle that points in the lateral direaction. The crystallites of the current verision are not highly realistic because they are monoclinic with a 60° angle mimicking a fraction of a hexagonal structure with hexagonal planes stacked in the z-direction. Inside the routine one can change between 2 or 3 different planes. Also the total crystallite size can be changed. Especially the parallelogram with 60° angle is unrealistic because one usually would assume the crystallites to have a hexagonal shape. However, the finite crystallites mimic the final correlation length inside the sample. The sample works for neutrons impingin from the sapphire, the silicon at grazing angles and in transmission in the sense of a SANS sample. If the neutrons impinge through the other layers (sample and silicon oxide) - the responses are not so realistic and need further development. Also multiple scattering would be needed to be implemented still - but could be done.
What this sample component covers relatively well is the fact that damping of the intensity by scattering and absorption is also covered. That means that even at larger angles than the critical angle the intensity is damped inside the sample and so only a certain near surface layer scatters neutrons. This effect is not covered by BornAgain.
I see this as a start for further developments.
Information extracted from malformatted docstrings follow:
the total thickness of the sandwich is zsapph+zsamp+zsilicon the thicknesses zsampsurf and zsiliconsurf are parts of the total sample/silicon thicknesses
(scattering length densitites, reciprocal total cross section of absorption, reciprocal total cross section of incoherent scattering) units rho... [A-2], abslen... [cm], inclen... [cm]
rhosapph, abslensapph, inclensapph for sapphire rhoD2O, abslenD2O, inclenD2O for D2O as solvent in sample rhoPS, abslenPS, inclenPS for polystyrene as colloids in sample
rhosiliconsurf, abslensiliconsurf, inclensiliconsurf for silicon surface (oxide layer)
rhosilicon, abslensilicon, inclensilicon for silicon
Input parameters
Parameters in boldface are required; the others are optional.
|
Name |
Unit |
Description |
Default |
|
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|
xwidth |
m |
Width of sample volume |
0.05 |
|
yheight |
m |
Height of sample volume |
0.15 |
|
zsapph |
m |
Thickness of the sapphire layer on one side |
0.02 |
|
zsamp |
m |
Thickness of the overall sample between sapphire and silicon |
0.002 |
|
zsampsurf |
m |
Thickness from the total of zsamp on either side of sapphire/silicon that is oriented |
0.000001 |
|
zsilicon |
m |
Thickness of the silicon layer on the other side |
0.02 |
|
zsiliconsurf |
m |
Thickness from the total of zsilicon on the sample side (oxidization layer) |
5e-9 |
|
rhosapph |
Å\(^{-2}\) |
Scattering length density of sapphire |
5.773e-6 |
|
abslensapph |
cm |
Absorption length of sapphire for 1 Å neutrons (scales with wavelength) |
163.708 |
|
inclensapph |
cm |
Incoherent scattering attenuation length of sapphire |
49.815 |
|
rhoD2O |
Å\(^{-2}\) |
Scattering length density of D2O |
6.364e-6 |
|
abslenD2O |
cm |
Absorption length of D2O for 1 Å neutrons (scales with wavelength) |
44066.347 |
|
inclenD2O |
cm |
Incoherent scattering attenuation length of D2O |
7.258 |
|
rhoPS |
Å\(^{-2}\) |
Scattering length density of the polystyrene colloids |
1.358e-6 |
|
abslenPS |
cm |
Absorption length of the polystyrene colloids for 1 Å neutrons (scales with wavelength) |
114.502 |
|
inclenPS |
cm |
Incoherent scattering attenuation length of the polystyrene colloids |
0.24588 |
|
rhosiliconsurf |
Å\(^{-2}\) |
Scattering length density of the silicon surface (oxidation) layer |
4.123e-6 |
|
abslensiliconsurf |
cm |
Absorption length of the silicon surface (oxide) layer for 1 Å neutrons (scales with wavelength) |
401.051 |
|
inclensiliconsurf |
cm |
Incoherent scattering attenuation length of the silicon surface (oxide) layer |
169.11 |
|
rhosilicon |
Å\(^{-2}\) |
Scattering length density of silicon |
2.079e-6 |
|
abslensilicon |
cm |
Absorption length of silicon for 1 Å neutrons (scales with wavelength) |
209.919 |
|
inclensilicon |
cm |
Incoherent scattering attenuation length of silicon |
9901.6 |
|
phiPS |
1 |
Concentration vol/vol of colloids in D2O |
0.1 |
|
Rad |
A |
Radius of colloids in Aangstroem |
370.0 |
|
phirot |
rad |
angle of the ordered (aligned) crytallites at the two surfaces towards sapphire/silicon |
0.0 |
|
sc_aim |
1 |
how much is scattered versus transmitted |
0.98 |
|
sans_aim |
1 |
how much goes to the small angle range versus wide angles |
0.98 |
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Links
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Component source code found in file GISANS_sample.comp.
