Module Elliptical Mirror

# VITESS Module Elliptical Mirror

The module mirror_elliptical simulates the neutron flight path through a ellipsoidal mirror calculating the intensity loss for each reflection (in dependence of the neutron wavelength and the incident angle). One needs to give three semi axes to describe the ellipsoid (please see the well known mathematical ellipsoid equation). One also has to give the center position of the ellipsoid. The ellipsoid can be rotated about one of the coordinate axis. Please choose X, Y and Z limits for the elliptical mirror. In this case, the ellipsoid will be cut by 6 planes X=Xmin, X=Xmax, Y=Ymin, Y=Ymax, Z=Zmin, Z=Zmax. So it is possible to create one or two mirrors or even an elliptical guide. The position of the origin for the next module has to be given as well.
Spin-up and spin-down neutrons can have different reflectivity curves. In this way, also polarisation can be treated. Additionally, the attenuation of the neutron beam in air of a certain humidity can be taken into account. Surface waviness is also considered. A visualization of the trajectories is possible (see figure).

Figure: Elliptical mirror

### Parameters for module 'quadr_field'

Parameter Unit | Description | Range or Values | Command Option
semi axis X, Y, Z [cm] | semi axes of the elliptic mirror in x-direction (beam), y-direction (left) and z-direction (up) | >0 | -a -b -c
Center position main X, Y, Z [cm] | x-, y- and z-component of the center of the ellipsoid | any | -d -e -k
Rotation angle [deg] | angle of rotation of the ellipsoid | [-90°,90°] | -g
Rotate around the axisfield range file | axis about which the ellipsoid is rotated | 'OX' 'OY' 'OZ' | -g
X_MIN, X_MAX [cm] | range (over which the mirror exists) in beam direction (x-axis) | -Axis_x<XMIN<XMAX<Axis_x | -A -C
Y_MIN, Y_MAX [cm] | range (over which the mirror exists) in horizontal direction perpendiculat to the beam (y-axis) | -Axis_y<YMIN<YMAX<Axis_y | -D -E
Z_MIN, Z_MAX [cm] | range (over which the mirror exists) in vertical direction (z-axis) | -Axis_z<ZMIN<ZMAX<Axis_z | -H -K
output X, Y, Z [cm] | x-, y- and z-component of the origin of the output frame (in the input frame) | any | -s -t -w
Activate visualisation | activation of visualisation of the neutron trajectories (see figure) | 'yes' 'no' | -y
Type of visualisation | plane to which the trajectories are projected for visualisation | 'XZ' 'XY' 'YZ' | -Y
Full visualisation | yes: visualisation of all neutrons paths no: only reflected neutrons are shown | 'yes' 'no' | -v
Output device | for Unix only: choice of output format | 'x-windows' 'ps file' | -l
Spin_up-/down reflectivity file | input data file containing the reflectivity curve R(Q) for spin-up and for spin-down neutrons resp. (in the same form as it is used in the guide module) | - | -i -I
surface waviness [deg] | amplitude of waviness of a rectangular distribution this value is the maximal angle of deviation of the surface normal from the ideal normal. | >=0 | -q
Reflected neutrons | yes: only reflected neutrons are treated further on no : all neutrons are treated further on | 'yes' 'no' | -u
Ideal reflection | yes: ideal reflection (R=1) no: reflectivity from files | 'yes' 'no' | -R
polarisation | yes: split into spin-down and spin-up reflectivity no: spin-up reflectivity for all neutrons | 'yes' 'no' | -p
neutron spin axis | axis for spin quantization | 'OX' 'OY' 'OZ' | -V
air humidity [%] | for 'air attenuation'='yes': relative air humidiy (at 293 K), used to calculate beam attenuation in air | [0,100] | -r
air attenuation | no: no attenuation of the neutron beam in air yes: activation of attenuation of the neutron beam in air for T=293 K and the given humidity | 'no' 'yes' | -z

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Last modified: Tue May 8 17:08:06 MET DST 2001