The `Collimator_radial` Component

A radial Soller collimator.

Identification

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

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.

When used as a focusing collimator, the focusing parameter should be set to 1.

An example of a instrument that uses this collimator can be found in the SALSA instrument,
in the example folder

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. If yheight_inner is specified, then this is the outer cylinders 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		Gives additional information.	0
approx		Use Soller triangular transmission approximation.	0
focusing	1	When set allows you to use the collimators for focusing, rather than dispersing.	0
yheight_inner			0

AT (	,	,		) RELATIVE
ROTATED (	,	,		) RELATIVE

The Collimator_radial Component

Identification

Description

Input parameters

Links

The `Collimator_radial` Component