This components may either set the flux or change it (filter-like), using
an external data filename.
Author: E. Farhi
Date: Dec, 15th, 2002
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:
You may use the 'thickness' and 'scaling' parameter for that purpose.
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'
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
in the component instance parameters.
Parameters in boldface are required;
the others are optional.
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
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.