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McStas: Selector

[ Identification | Description | Input parameters | Links ]

The Selector Component

velocity selector (helical lamella type) such as V_selector component


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


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.
xminmLower x bound of entry aperture-0.015
xmaxmUpper x bound of entry aperture0.015
yminmLower y bound of entry aperture-0.025
ymaxmUpper y bound of entry aperture0.025
lengthmrotor length0.25
xwidthmWidth of entry. Overrides xmin,xmax.0
yheightmHeight of entry. Overrides ymin,ymax.0
nslit1number of absorbing subdivinding spokes/lamella72
dmwidth of spokes at beam-center0.0004
radiusmradius of beam-center0.12
alphadegangle of torsion48.298
nuHzfrequency of rotation, which is ideally 3956*alpha*DEG2RAD/2/PI/lambda/length500


[ Identification | Description | Input parameters | Links ]

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

Last Modified: Tuesday, 16-Apr-2024 20:05:20 CEST
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