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10.7 The DivPos_monitor McStas Component
Divergence/position monitor (acceptance diagram).
Identification
-
Author: Kristian Nielsen
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Origin: Risoe
-
Date: 1999
Description
2D detector for intensity as a function of position and divergence, either horizontally or vertically (depending on the flag vertical). This gives information similar to an aceptance diagram used eg. to investigate beam profiles in neutron guides.
Example: DivPos_monitor(nh=20, ndiv=20, filename="Output.dip", xmin=-0.1, xmax=0.1, ymin=-0.1, ymax=0.1, maxdiv_h=2)
Input parameters
Parameters in boldface are required; the others are optional.
|
Name |
Unit |
Description |
Default |
|
|
|||
|
nb |
1 |
Number of bins in position. |
20 |
|
ndiv |
1 |
Number of bins in divergence. |
20 |
|
filename |
string |
Name of file in which to store the detector image. |
0 |
|
xmin |
m |
Lower x bound of detector opening |
-0.05 |
|
xmax |
m |
Upper x bound of detector opening |
0.05 |
|
ymin |
m |
Lower y bound of detector opening |
-0.05 |
|
ymax |
m |
Upper y bound of detector opening |
0.05 |
|
xwidth |
m |
Width of detector. Overrides xmin,xmax. |
0 |
|
yheight |
m |
Height of detector. Overrides ymin,ymax. |
0 |
|
maxdiv |
degrees |
Maximal divergence detected. |
2 |
|
restore_neutron |
1 |
If set, the monitor does not influence the neutron state. |
0 |
|
nx |
1 |
x-component of the "forward" direction vector (see ny) |
0 |
|
ny |
1 |
Vector definition of "forward" direction wrt. divergence, to be used e.g. when the monitor is rotated into the horizontal plane |
0 |
|
nz |
1 |
z-component of the "forward" direction vector (see ny) |
1 |
|
vertical |
1 |
Monitor intensity as a function of vertical divergence and position. |
0 |
|
nowritefile |
1 |
If set, monitor will skip writing to disk CALCULATED PARAMETERS: |
0 |
|
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Links
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Component source code found in file DivPos_monitor.comp.
A divergence and position sensitive monitor
DivPos_monitor is a two-dimensional monitor component, which is sensitive to both horizontal position (\(x\)) and horizontal divergence defined by \(\eta _\textrm {h} = \tan ^{-1}(v_x/v_z)\). The detector window is set by the \(x\) and \(y\) input coordinates.
The neutron counts are being histogrammed into \(n_x \times n_\textrm {h}\) pixels. The horizontal divergence range accepted is \([-\eta _\textrm {h,max}; \eta _\textrm {h,max}]\), and the horizontal position range is the size of the detector.
The output from PSD_monitor is the integrated counts, \(n, I, M_2\), as well as three two-dimensional arrays of counts: \(n(x,\eta _\textrm {h}), I(x,\eta _\textrm {h}), M_2(x,\eta _\textrm {h})\). The arrays are written to a file and can be read e.g. by the tool mcplot, see the system manual.
This component can be used for measuring acceptance diagrams [Cus03]. PSD_monitor can easily be changed into being sensitive to \(y\) and vertical divergence by a 90 degree rotation around the \(z\)-axis.
