[ Identification | Description | Input parameters | Links ]

The Filter_gen Component

This components may either set the flux or change it (filter-like), using an external data filename.

Identification

• Site:
• Author: E. Farhi
• Origin: ILL
• Date: Dec, 15th, 2002

Description

This component changes the neutron flux (weight) in order to match
a reference table in a filename.
Typically you may set the neutron flux (source-like), or multiply it
using a transmission table (filter-like).
The component may be placed after a source, in order to e.g.
simulate a real source from a reference table, or used as a filter (BeO)
or as a window (Al). The behaviour of the component is
specified using the 'options' parameter, or from the filename itself (see below)
If the thickness for the transmission data filename D was t0, and a different
thickness t1 would be required, then the resulting transmission is:
D^(t1/t0).
You may use the 'thickness' and 'scaling' parameter for that purpose.

File format:
This filename may be of any 2-columns free format (k[Angs-1],p), (omega[meV],p)
and (lambda[Angs],p) where p is the weight. The type of the filename may be
written explicitely in the filename, as a comment, or using the 'options'
parameter.
Non mumerical content in filename is treated as comment (e.g. lines starting
with '#' character).
A table rebinning and linear interpolation are performed.

EXAMPLE : in order to simulate a PG filter, using the lib/data/HOPG.trm file
Filter_gen(xwidth=.1 yheight=.1, filename="HOPG.trm")
A Sapphire filter, using the lib/data/Al2O3_sapphire.trm file
Filter_gen(xwidth=.1 yheight=.1, filename="Al2O3_sapphire.trm")
A Berylium filter, using the lib/data/Be.trm file
Filter_gen(xwidth=.1 yheight=.1, filename="Be.trm")
an other possibility to simulate a Be filter is to use the PowderN component:
PowderN(xwidth=.1, yheight=.1, zdepth=.1, reflections="Be.laz", p_inc=1e-4)

in this filename, the comment line
# wavevector multiply
sets the behaviour of the component. One may as well have used
options="wavevector multiply"
in the component instance parameters.

Input parameters

Parameters in boldface are required; the others are optional.

Name	Unit	Description	Default
filename	str	name of the filename to look at (first two columns data). Data D should rather be sorted (ascending order) and monotonic filename may contain options (see below) as comment	0
options	str	string that can contain: "[ k p ]" or "wavevector" for filename type, "[ omega p]" or "energy", "[ lambda p ]" or "wavelength", "set" to set the weight according to the table,"multiply" to multiply (instead of set) the weight by factor,"add" to add to current flux,"verbose" to display additional informations.	0
xmin	m	dimension of filter	-0.05
xmax	m	dimension of filter	0.05
ymin	m	dimension of filter	-0.05
ymax	m	dimension of filter	0.05
xwidth	m	Width/diameter of filter). Overrides xmin,xmax.	0
yheight	m	Height of filter. Overrides ymin,ymax.	0
thickness	1	relative thickness. D = D^(thickness).	1
scaling	1	scaling factor. D = D*scaling.	1
verbose			0

AT (	,	,		) RELATIVE		Generate
ROTATED (	,	,		) RELATIVE

Links

• Source code for Filter_gen.comp.
• HOPG.trm filename as an example.

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[ Identification | Description | Input parameters | Links ]

Generated on 2025-05-08 13:31:31

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Last Modified: Monday, 30-Jun-2025 11:05:10 CEST