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.