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: Test_Sqw_monitor

[ Identification | Description | Input parameters | Links ]

The Test_Sqw_monitor Instrument

A simple ToF with cylindrical/spherical sample, and furnace/cryostat/container. The sample can be hollow.


  • Site: Tests_samples
  • Author: E. Farhi
  • Origin: ILL
  • Date: Feb 2014


This instrument models a generic, tunable, neutron time-of-flight spectrometer.

The incoming flux at the sample brings neutrons with 'beam_wavelength_Angs' wavelength.
The energy resolution at the sample is given as 'beam_resolution_meV'.
The beam size at the sample is set to the sample cross section (e.g. ~2 x 5 cm).

The sample geometry is either cylindrical ('sample_radius_m' and 'sample_height_m')
or spherical ('sample_height_m=0'). The sample can be hollow when given a thickness
'sample_thickness_m', or filled ('sample_thickness_m=0'). When in cylindrical geometry,
it is surrounded by a container with thickness 'container_thickness_m'. The container
material is specified as a powder file name 'container' in the McStas Sqw or PowderN format,
e.g. 'Al.laz' or 'Nb.laz'. Setting 'container=0' removes the container.

The sample scattering is characterised by its coherent and incoherent contributions
given as 'sample_coh' and 'sample_inc' file names in McStas Sqw or PowderN format.
Setting the 'sample_coh=sample_inc=0' removes the sample, e.g. to study the container or
environment only contribution.

The sample and its container are located inside a cylindrical shield with radius
'environment_radius_m' and thickness 'environment_thickness_m'. The material is set from
the 'environment' file name in the McStas Sqw or PowderN format (e.g. 'Al.laz').
This way, it is possible to estimate the contribution of a cryostat or furnace.
Setting 'environment=0' removes the environment.

The detector has a cylindrical geometry, with a radius 'sample_detector_distance_m'
and tubes with height 'detector_height_m'. The detector covers a -30 to 140 deg angular range
with 2.54 cm diameter tubes (the number of tubes is computed from the distance).
The direct beam (non scattered neutrons) is discarded.

The detector produces both (angle,tof) and (q,w) data sets, for:
total scattering
coherent single scattering from sample
incoherent single scattering from sample
multiple scattering from sample
scattering from the container and sample environment
The (angle,tof) results are corrected for the parallax effect from the detector height.

Known configurations:
beam_wavelength_Angs=2, beam_resolution_meV=0.5,
sample_detector_distance_m=2.0, detector_height_m=0.3
beam_wavelength_Angs=5, beam_resolution_meV=0.1,
sample_detector_distance_m=4.0, detector_height_m=3.0
beam_wavelength_Angs=4.1, beam_resolution_meV=0.1,
sample_detector_distance_m=2.48, detector_height_m=1.2
beam_wavelength_Angs=4.1, beam_resolution_meV=0.1,
sample_detector_distance_m=2.5, detector_height_m=1.2
beam_wavelength_Angs=3.0, beam_resolution_meV=0.3,
sample_detector_distance_m=4.0, detector_height_m=2.0
beam_wavelength_Angs=1.0, beam_resolution_meV=3.0,
sample_detector_distance_m=5.5, detector_height_m=1.2
beam_wavelength_Angs=0.3, beam_resolution_meV=20.0,
sample_detector_distance_m=3.0, detector_height_m=1.46
beam_wavelength_Angs=3.0, beam_resolution_meV=0.2,
sample_detector_distance_m=4.0, detector_height_m=1.2
beam_wavelength_Angs=1.0, beam_resolution_meV=2.4,
sample_detector_distance_m=2.5, detector_height_m=3.0
beam_wavelength_Angs=4.0, beam_resolution_meV=0.1,
sample_detector_distance_m=3.5, detector_height_m=4.0

Input parameters

Parameters in boldface are required; the others are optional.
beam_wavelength_AngsAngsincident neutron beam wavelength2
beam_resolution_meVmeVincident energy range full width0.1
sample_cohstrsample coherent Sqw data file or NULL"Rb_liq_coh.sqw"
sample_incstrsample incoherent Sqw data file or NULL"Rb_liq_inc.sqw"
sample_thickness_mmthickness of sample. 0=filled1e-3
sample_height_mmheight of sample. 0=sphere0.03
sample_radius_mmradius of sample (outer)0.005
containerstrcontainer material or NULL"Al.laz"
container_thickness_mmcontainer thickness50e-6
environmentstr sample environment material or NULL"Al.laz"
environment_radius_mmsample environment outer radius0.025
environment_thickness_mmsample environment thickness2e-3
detector_height_mmdetector tubes height3
sample_detector_distance_mmdistance from sample to detector4.0


[ Identification | Description | Input parameters | Links ]

Generated on 2024-01-03 11:47:43

Last Modified: Tuesday, 16-Apr-2024 20:05:22 CEST
Search website mailinglist archive GitHub repos