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3.2 The Source_flat McXtrace Component
Release: McXtrace 0.1_alpha
A flat rectangular or circular surface emitting x-rays
Identification
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Author: Erik Knudsen
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Origin: Risoe
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Date: September 25, 2009
Description
A circular or rectangular xray source. Spectrum may be either gaussian or uniform around a central wavelength/energy or read from a datafile. Xrays are considered emitted uniformly into 4pi, but a square target retricts the beam to that window and scales the beam intensity accordingly. If an input spectrum datafile (spectrum_file) is not specified, the beam is restricted to emit photons between E0+-dE keV, or lambda0+-dlambda Å, whichever is given. The input spectrum file should be formatted such that x-ray energy/wavelength is in the first column and the intensity in the second. Any preceding lines starting with # are considered part of the file header. If a datafile is given, a nonzero E0 value indicates that is is parametrized by energy (in keV) as opposed to wavelength (in Å). Wavelength is the default. Flux is set in the unit photons/s
Example: Source_flat(xwidth=1e-3,yheight=1e-3, focus_xw=0.5e-2, focus_yh=0.45e-2,dist=1, E0=E0, dE=DE)
Input parameters
Parameters in boldface are required; the others are optional.
|
Name |
Unit |
Description |
Default |
|
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|
radius |
m |
Radius of circle in (x,y,0) plane where x-rays are generated. |
0 |
|
yheight |
m |
Height of rectangle in (x,y,0) plane where x-rays are generated. |
0 |
|
xwidth |
m |
Width of rectangle in (x,y,0) plane where x-rays are generated. Overrides xmin and xmax. |
0 |
|
xmin |
m |
Lower bound of x-interval where photons are generated. |
0 |
|
xmax |
m |
Upper bound of x-interval where photons are generated. |
0 |
|
dist |
m |
Distance to target along z axis. |
0 |
|
focus_xw |
m |
Width of target |
.045 |
|
focus_yh |
m |
Height of target |
.12 |
|
E0 |
keV |
Mean energy of xrays. |
0 |
|
dE |
keV |
Energy half spread of x-rays (flat or gaussian sigma). |
0 |
|
lambda0 |
Å |
Mean wavelength of x-rays. |
0 |
|
dlambda |
Å |
Wavelength half spread of x-rays. |
0 |
|
flux |
pht/s |
Total flux radiated from the source |
0 |
|
gauss |
1 |
Gaussian (1) or Flat (0) energy/wavelength distribution |
0 |
|
randomphase |
|
If nonzero, the phase of the emotted photon is random, i.e. source is fully incoherent. otherwise the value of phase is used. |
1 |
|
phase |
rad |
Set phase to something given. |
0 |
|
spectrum_file |
string |
Filename for optional spectrum-file |
”” |
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Links
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Component source code found in file Source_flat.comp.
A flat surface emitting photons with a spectrum either uniform, gaussian or generated from a datafile
A simple source model, with a flat surface emitting photons. The surface in the \(xy\)-plane is specified as a rectangle with dimensions \(\mathit {xwidth}\times \mathit {yheight}\) \(\mathrm {m}^{2}\), or as a circle with radius \(\mathrm {m}\). The initial x-ray position is chosen randomly in the source surface — its wavevector is chosen randomly (exactly as in the case of Source_pt) (section 3.1) in the defining aperture with height focus_yh and width focus_xw placed at \((0,0,\mathit {dist})\).
Just as for Source_pt the aperture is for efficiency purposes and, if misused, may cause biasing.
With the exception of source size related parameters, all other parameters are identical to Source_pt Note that this also applies to coherence and photon phase. If randomphase\(=0\) then a photon emitted from \((x_0,y_0,0)\) will in phase with a photon emitted from \((x_1,y_1,0)\). I.e. full transversal coherence.
