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McStas: Collimator_radial

[ Identification | Description | Input parameters | Links ]

The Collimator_radial Component

A radial Soller collimator.


  • Site:
  • Author: Emmanuel Farhi
  • Origin: ILL
  • Date: July 2005


Radial Soller collimator with rectangular opening and specified length.
The collimator is made of many rectangular channels stacked radially.
Each channel is a set of transmitting layers (nslit), separated by an absorbing
material (infinitely thin), the whole stuff is inside an absorbing housing.

When specifying the number of channels (nchan), each channel has a total
entrance width=radius*fabs(theta_max-theta_min)/nchan, but only the central
portion 'xwidth' accepts neutrons. When xwidth=0, it is set to the full
apperture so that all neutrons enter the channels (all walls are infinitely thin).

When using zero as the number of channels (nchan), the collimator is continuous,
whithout shadowing effect.

The component should be positioned at the radius center.
The component can be made oscillating (usual on diffractometers and TOF
machines) with the 'roc' parameter.
The neutron beam outside the collimator angular area is transmitted unaffected.

Channelled radial collimator with shadow parts
Collimator_radial(xwidth=0.015, yheight=.3, length=.35, divergence=40,transmission=1, theta_min=5, theta_max=165, nchan=128, radius=0.9)
A continuous radial collimator
Collimator_radial(yheight=.3, length=.35, divergence=40,transmission=1, theta_min=5, theta_max=165, radius=0.9)

Input parameters

Parameters in boldface are required; the others are optional.
xwidthmSoller window width, filled with nslit slits. Use 0 value for continuous collimator.0
yheightmCollimator height..3
lengthmLength/Distance between inner and outer slits..35
divergencemin of arcDivergence angle. May also be specified with the nslit parameter. A zero value unactivates component.0
transmission1Maximum transmission of Soller (0<=t<=1).1
theta_mindegMinimum Theta angle for the radial setting.5
theta_maxdegMaximum Theta angle for the radial setting.165
nchan1Number of Soller channels in the theta range. Use 0 value for continuous collimator.0
radiusmRadius of the collimator (to entry window).1.3
nslit1Number of blades composing each Soller. Overrides the divergence parameter.0
rocdegAmplitude of oscillation of collimator. 0=fixed.0
verboseGives additional information.0
approxUse Soller triangular transmission approximation.0


[ Identification | Description | Input parameters | Links ]

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

Last Modified: Tuesday, 16-Apr-2024 20:05:22 CEST
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