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: SEMSANS_Delft

[ Identification | Description | Input parameters | Links ]

The SEMSANS_Delft Instrument

Idealised SESANS instrument using magnetised foil flippers with realistic sample


  • Site: Reactor_Institute_Delft
  • Author: Wim Bouwman (, Peter Willendrup and Erik Knudsen
  • Origin: Delft University of Technology
  • Date: December 2019


A full description of the instrument can be found in J. Appl. Cryst. (2021) V. 54
The instrument has the bare essentials to simulate the Larmor precession of the neutron spins in the foil flippers and the
geometry and wavelength distribution of a version of SEMSANS that can be made from the SESANS in Delft as described in
Physica B 406(2011)2357–2360
An essential component is the realistic SANS sample, describing both the scattered and transmitted neutron, including multiple scattering.
For a full SEMSANS scan the applied magnetic field By has to be scanned.
It is best to run it twice with the analyser in up and down orientation.
In principle the sample can be removed to study the empty beam instrument, which with this idealised setup have perfect polarisation.
It is possible to monitor the evolution of the polarisation with several polarisation monitors that have beeen commented in this version.
The foil-angle, thickness and wavelength yield now matched parameters to have the SESANS working.
These parameter and the sphere radius match now with the magnetic fields below to get a good measurement range.
A pretty high number of neutrons is needed to get good statistics in the fine position sensitive detector.

SESANS_Delft -n 100000000 -N 31 L0=2.165 DL=0.02 By=0,0.0468 AnaSign=1
SESANS_Delft -n 100000000 -N 31 L0=2.165 DL=0.02 By=0,0.0468 AnaSign=-1

Input parameters

Parameters in boldface are required; the others are optional.
L0AAnominal wavelength2.165
DLAAwavelength band width0.02
ByTApplied magnetic field in foil flippers4.68e-3
AnaSignDirection of analyser (-1 or 1)1


[ Identification | Description | Input parameters | Links ]

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

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