McStas logo McStas - A neutron ray-trace simulation package ILL; PSI; ESS Niels Bohr Institute DTU Physics NEXMAP


About McStas
 Conditions of use
 Project funding

 Other Downloads (share)

Mailing list

Search web/mailinglist

 Wiki (GitHub)
 McStas manual


Report bugs (GitHub)

Code-repository (GitHub)

McStas: SANS_spheres2

[ Identification | Description | Input parameters | Links ]

The SANS_spheres2 Component


  • Site:
  • Author: P. Willendrup, derived from H. Frielinghaus SANS_benchmark2
  • Origin:
  • Date: 16.12.2019


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.
xwidthmWidth of sample volume0.01
yheightmHeight of sample volume0.01
zthickmThickness of sample volume0.001
dsdw_inccm^-1The 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 D2O0.02
sc_aim1The fraction of neutron paths used to represent the scattered neutrons (including everything: incoherent and coherent). rest is transmission.0.97
sans_aim1The 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
RAARadius of dilute, monodisperse spheres150
phi1Volume-ratio of the spheres wrt. solution1e-3
drhocm^-2Scattering length density6e10
singlesp1Switches 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
QmindAA^-1Lower limit of "SANS" scattering0.0001
QmaxdAA^-1Upper limit of "SANS" scattering2.1544346900319


[ Identification | Description | Input parameters | Links ]

Generated on 2023-09-19 20:01:36

Last Modified: Tuesday, 16-Apr-2024 20:05:21 CEST
Search website mailinglist archive GitHub repos