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: Selector Component

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

The Selector Component

velocity selector (helical lamella type) such as V_selector component


  • Author: Peter Link, Andreas Ostermann
  • Origin: Uni. Gottingen (Germany)
  • Date: MARCH 1999
  • Version:(Unknown)


Velocity selector consisting of rotating Soller-like blades
defining a helically twisted passage.
Geometry is defined by two identical apertures at 12 o'clock position,
The origin is at the ENTRANCE of the selector.

Example: Selector(xmin=-0.015,  xmax=0.015,  ymin=-0.025, ymax=0.025, length=0.25,
           nslit=72,d=0.0004, radius=0.12, alpha=48.298, nu=500)
These are values for the D11@ILL Dornier 'Dolores' Velocity Selector (NVS 023)

Jun 2005: extensive external test, one minor problem
Jan 2006: problem solved (for McStas-1.9.1)
Validated by: K. Lieutenant

for transmission calculation, each neutron is supposed to be in the guide centre

Input parameters

Parameters in boldface are required; the others are optional.
Name Unit Description Default
xmin m Lower x bound of entry aperture -0.015
xmax m Upper x bound of entry aperture 0.015
ymin m Lower y bound of entry aperture -0.025
ymax m Upper y bound of entry aperture 0.025
length m rotor length 0.25
xwidth m Width of entry. Overrides xmin,xmax. 0
yheight m Height of entry. Overrides ymin,ymax. 0
nslit 1 number of absorbing subdivinding spokes/lamella 72
d m width of spokes at beam-center 0.0004
radius m radius of beam-center 0.12
alpha deg angle of torsion 48.298
nu Hz frequency of rotation, which is ideally 3956*alpha*DEG2RAD/2/PI/lambda/length 500


[ 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
Search website mailinglist archive GitHub repos