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3.3 The Source_div McXtrace Component
Release: McXtrace 0.1
X-ray source with Gaussian or uniform divergence
Identification
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Author: Erik Knudsen
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Origin: Risoe
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Date: November 11, 2009
Description
A flat rectangular surface source with uniform or Gaussian divergence profile and focussing. If the parametere gauss is not set (the default) the divergence profile is flat in the range [-focus_ax,focus_ay]. If gauss is set, the focux_ax,focus_ay is considered the standard deviation of the gaussian profile. Currently focussing is only active for flat profile. The ”focus window” is defined by focus_xw,focus_yh and dist. The spectral intensity profile is uniformly distributed in the energy interval defined by e0+-dE/2 or by wavelength lambda0+-dlambda/2
Example: Source_div(xwidth=0.1, yheight=0.1, focus_aw=2, focus_ah=2, E0=14, dE=2, gauss=0)
Input parameters
Parameters in boldface are required; the others are optional.
|
Name |
Unit |
Description |
Default |
|
|
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|
spectrum_file |
string |
File from which to read the spectral intensity profile |
”NULL” |
|
xwidth |
m |
Width of source. |
0 |
|
yheight |
m |
Height of source. |
0 |
|
dist |
m |
Downstream distance to place sampling target window |
0 |
|
focus_xw |
m |
Width of sampling window |
0 |
|
focus_yh |
m |
Height of sampling window |
0 |
|
focus_aw |
rad |
Standard deviation (Gaussian) or maximal (uniform) horz. width divergence. |
0 |
|
focus_ah |
rad |
Standard deviation (Gaussian) or maximal (uniform) vert. height divergence. |
0 |
|
focus_ar |
rad |
Standard deviation (Gaussian) or maximal (uniform) radial divergence. |
0 |
|
radius |
m |
Radius of circular source |
0 |
|
E0 |
keV |
Mean energy of X-rays. |
0 |
|
dE |
keV |
Energy half spread of X-rays. If gauss==0 dE is the half-spread, i.e. E∖in[E0-dE,E0+dE], if gauss!=0 it’s interpreted as the standard dev. |
0 |
|
lambda0 |
Å |
Mean wavelength of X-rays (only relevant for E0=0). |
0 |
|
dlambda |
Å |
Wavelength half spread of X-rays. |
0 |
|
flux |
1/(s * mm**2 *mrad**2 * energy unit) |
flux per energy unit, Å or keV. |
0 |
|
gauss |
1 |
Criterion: 0: uniform, 1: Gaussian distribution of energy/wavelength. |
0 |
|
gauss_a |
1 |
Criterion: 0: uniform, 1: Gaussian divergence distribution. |
0 |
|
randomphase |
1 |
If !=0 the photon phase is chosen randomly. |
1 |
|
phase |
1 |
Value of the photon phase (if randomphase==0). |
0 |
|
verbose |
0/1 |
Show more information |
0 |
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Links
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Component source code found in file Source_div.comp.
A continuous source with specified divergence
Source_div is a rectangular source, \(w \times h\), which emits a beam of a specified divergence around the direction of the \(z\)-axis.
Just as for Source_pt, if a spectrum_file is not supplied, the xray is given a weight which is the total wavelength-integrated intensity downscaled by the solid angle subtended by the defining aperture and the energy/wavlength spectrum is centered around E0 or \(\lambda 0\) with width dE or \(d\lambda \) respectively. The profile is Gaussian if gauss\(\neq 0\), uniform if gauss\(=0\), If a spectrum_file is supplied, a slightly different strategy is adopted. In this case the wavelength/energy range implied by the datafile is sampled unformly and each ray is assigned a weight corresponding to the intensity indicated by linear interpolation between datapoints at that wavelength. This implies an oversampling of weak parts of the intensity spectrum.
The beam intensity is uniform over the whole of the source and the source divergences are focus_ah and focus_aw in degrees. Unless gauss_a\(\neq =0\) the individual photons are sampled from a uniform divergence distribution, otherwise a Gaussian is used.
