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3.4 The Source_gaussian McXtrace Component
Gaussian cross-section source
Identification
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Author: Jana Baltser & Erik Knudsen
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Origin: NBI
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Date: April, 2011.
Description
A simple source model emitting photons from a gaussian distribution in the X-Y plane with the specified standard deviations and divergence. A square target centered on the beam (Z-axis) may be used to restrict the beam to that aperture. If no target aperture is given the full gaussian cross-section is used. Further, the beam is restricted to emit photons between E0+-dE keV, or lambda0+-dlambda, whichever is given, if a spectrum_file is not specified, in which case the contents of the file dictates the emitted spectrum.
Example: Source_gaussian(sig_x=10e-6,sig_y=10e-6,dist=15,sigPr_x=9e-6, sigPr_y=9e-6,E0=12.5, dE=0.1)
Input parameters
Parameters in boldface are required; the others are optional.
|
Name |
Unit |
Description |
Default |
|
|
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|
spectrum_file |
|
File from which to read the spectral intensity profile |
”NULL” |
|
sig_x |
m |
Horizontal standard deviation of source (rms source size). |
1 |
|
sig_y |
m |
Vertical standard deviation of source (rms source size). |
0 |
|
sigPr_x |
rad |
Angular horizontal divergence |
0 |
|
sigPr_y |
rad |
Angular vertical divergence Optional Parameters: |
0 |
|
flux |
|
Scaling factor to set the total emitted unrestricted flux. |
1 |
|
brilliance |
|
Unit in spectrum_file is Brilliance - apply corrections to get to raw flux. |
0 |
|
dist |
m |
Distance from source plane to sampling window. |
1 |
|
gauss |
0/1 |
Gaussian (1) or uniform (0) spectrum profile. |
0 |
|
focus_xw |
m |
Width of sampling window dist m downstream from source to allow focused sampling. |
0 |
|
focus_yh |
m |
Height of sampling window dist m downstream from source to allow focused sampling. |
0 |
|
E0 |
keV |
Centre of emitted energy spectrum (overrides spectrum_file) |
0 |
|
dE |
kev |
Half-width (or std. dev.) of emitted energy spectrum. |
0 |
|
lambda0 |
Å |
Centre of emitted wavelength spectrum. |
0 |
|
dlambda |
Å |
Half-width (or std. dev.) of emitted wavelength spectrum. |
-1 |
|
phase |
rad |
The initial phase of the photons. |
0 |
|
randomphase |
rad |
If nonzero phase is random (incoherent radiation), otherwise it is set to the value of phase |
1 |
|
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Links
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Component source code found in file Source_gaussian.comp.
the model has a gaussian distribution of intensity
A simplified version of a completely incoherent source of horizontal and vertical sizes sig_x and sig_y respectively with angular divergence sigPr_x and sigPr_y. Can be used to model an undulator source emitting a photon beam that has gaussian distribution. This naturally generates a larger Gaussian profile at a distance. A sampling window at \((0,0,\mathit {dist})\) may be specified by the parameters focus_xw and focus_yh, which restricts the sampling phases space of the emitted photons (See section 3.1 for details).
The energy spectrum emitted by Source_gaussian source is completely analogous to Source_pt, as is its photon phase functionality.
