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McStas: Collimator_radial Component

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

The Collimator_radial Component

A radial Soller collimator.

Identification

  • Author: Emmanuel Farhi
  • Origin: ILL
  • Date: July 2005
  • Version: $Revision$

Description

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.

Example: 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.
Name Unit Description Default
xwidth m Soller window width, filled with nslit slits. Use 0 value for continuous collimator. 0
yheight m Collimator height. .3
length m Length/Distance between inner and outer slits. .35
divergence min of arc Divergence angle. May also be specified with the nslit parameter. A zero value unactivates component. 0
transmission 1 Maximum transmission of Soller (0<=t<=1). 1
theta_min deg Minimum Theta angle for the radial setting. 5
theta_max deg Maximum Theta angle for the radial setting. 165
nchan 1 Number of Soller channels in the theta range. Use 0 value for continuous collimator. 0
radius m Radius of the collimator (to entry window). 1.3
nslit 1 Number of blades composing each Soller. Overrides the divergence parameter. 0
roc deg Amplitude of oscillation of collimator. 0=fixed. 0
verbose 0/1 Gives additional information. 0
approx 0/1 Use Soller triangular transmission approximation. 0

Output parameters

Name Unit Description Default
width_of_slit  
width_of_Soller  
slit_theta  

Links


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

Generated automatically by McDoc, Peter Willendrup <peter.willendrup@risoe.dk> / Fri Mar 17 20:40:06 2017


Last Modified: Friday, 17-Mar-2017 21:40:06 CET
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