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McStas: Bender

[ Identification | Description | Input parameters | Links ]

The Bender Component

Models a curved neutron guide.


  • Site:
  • Author: Philipp Bernhardt
  • Origin: Uni. Erlangen (Germany)
  • Date: Februar 7 1999


Models a curved neutron guide with cylindrical walls.

Bender radius, entrance width and height are necessary input data. To define
the bender, you may either enter the deviation angle 'Win' or the length 'l'.
The bender may consist of 'k' vertical channels, separated by partitioning walls
of thickness 'd'. Three different reflectivity profiles can be given: for outer
walls, for inner walls and for the top and bottom walls. The partitioning walls
have the same coating as the exterior walls.

The entrance lies in the X-Y plane, centered on the Z axis. The neutrons will
also leave the bender in the X-Y plane at the z-value l=r*Win, i.e. they are
centred on (0,0,r*Win); they have an (average) flight direction along the z-axis.
Therefore, the following component is adjacent, if positioned AT (0,0,r*Win)
without rotation.
So, seen from outside, it behaves like a straight guide along the Z axis. As a
consequence, it is shown straight in 'mcdisplay'.
This behaviour results from a co-ordinate transformation inside the component.
It is done to facilitate its use. Neither rotation nor shift along the x-axis
need to be calculated; a new arm is not necessary. Internally, the bender is
bent to the negative X axis;

Bender of 120 mm height, 50 mm width, 250 m radius and 0.04 rad (or 2.292 deg) curvature
not channeled, with a standard m=2 coating on


Some users have reported potentially strange behaviours with this component.
This component does not work with gravitation on.

Input parameters

Parameters in boldface are required; the others are optional.
wmWidth at the bender entry and exit
hmHeight at the bender entry and exit
rmRadius of the bender
WinradAngle of the deflection of the whole bender0.04
k1Number of channels inside the bender1
dmThickness of one blade separating the channels0.001
lmlength of bender l=r*Win0
R0a1Low-angle reflectivity at the outer side of the bender0.99
QcaAA-1Critical scattering vector0.021
alphaaAASlope of reflectivity6.07
ma1m-value of material2
WaAA-1Width of supermirror cut-off0.003
R0i1Low-angle reflectivity at the inner side of the bender0.99
QciAA-1Critical scattering vector0.021
alphaiAASlope of reflectivity6.07
mi1m-value of material2
WiAA-1Width of supermirror cut-off0.003
R0s1Low-angle reflectivity at the top and bottom side of the bender0.99
QcsAA-1Critical scattering vector0.021
alphasAASlope of reflectivity6.07
ms1m-value of material2
WsAA-1Width of supermirror cut-off0.003


[ 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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