The module evaluation-elast refers always to the detector output
(i.e. the previous VITESS module must be the detector module, the detector
output contains angle definitions which differ from the conventions used by
other modules) and transforms it to presentable data files with reference to
typical physical parameters of interest. The data of these files can be
visualised by appropriate means, e.g. 'Origin', or one can try to use the
plot facilities of the VITESS GUI. This module should be used for elastic
scattering (e.g. powder diffraction, SANS).
The spectra file will contain the neutron probabilities counted for each
segment of the evaluation interval (with respect to the evaluation parameter
of interest).
The following information has to be given as an input:
evaluation parameter: choose between d-spacing, momentum transfer Q,
scattering angle, and difference between wavelength from TOF and true
wavelength.
spectra file: the name of the spectra file which will contain
the evaluated data has to be given.
number of bins: number of bins determines the segmentation of the d-spacing,
momentum transfer, scattering angle, or wavelength difference and therewith
the number of values written to the spectra file.
minimum, maximum: the bounds of the interval for the evaluation parameter.
increase to next bin: for a logarithmic binning the percentage has to be given
by which the upper limit of each bin exceeds its lower limit.
If this value is set, the given 'number of bins' is ignored
dead-spot: only needed if the direct beam points to the detector
(as in the case of SANS).
All neutrons with a scattering angle(2 theta) between 0 and dead-spot [deg]
will therefore not be considered in the evaluation.
probability weight: if one deactivates the probability weight each
neutron is considered with the weight 1, otherwise (default)
the attributed probabilities (due to the operations of the modules before)
are considered.
time of flight: if the wavelength of the neutrons shall be
determined by time of flight analysis (i.e. each wavelength is
calculated from the flight path and the flight time)
this option must be activated.
flight path [cm]: length of total neutron flight path,
needed only for time of flight analysis.
time offset [ms]: global shift of the neutron time t t-TimeOffset [ms],
useful to shift the temporal reference point for the time of flight analysis
reference wavelength [A]: needed only for conventional evaluation
(non-time of flight case), i.e. a crystal monochromator or velocity
selector was used. In this case one must know which ideal wavelength
should be assumed in the evaluation.
begin, end of evaluation: the bounds of the time interval for the evaluation.
Only neutrons arriving in that time interval are considered in the
evaluation
The following input parameters refer to a special application which is
useful especially for integrating the peak intensities of a powder
spectrum within the evaluation interval.
intensity file: it will contain the integrated intensities for certain
ranges within the evaluation interval defined above.
The ranges and the range centres have to be defined in the info file.
If no intensity file name is given this special application will
not be activated.
info file:
it is needed if one wants to generate an intensity file!
The info file then has to be defined before running this module
simply as a data file as follows:
each integration range is defined with two numbers. The first number gives
the centre of the integration interval (this corresponds e.g. to a powder
peak), the second number defines the width of the integration interval.
For each integration range a new line must be used.
Example:
0.1 0.2
0.3 0.1
First line means: integration between 0.0 and 0.2, the result of the
integration refers to the interval centre 0.1.
Second line means integration between 0.22 and 0.35, the result of the
integration refers to the interval centre 0.3.
Maybe one needs information from the spectra file to define the info
file appropriately. Then first a run only to generate the spectra
file is recommended
!!!! Note: the info file ranges must be defined appropriately
that they lie within the evaluation interval !!!!
Last modified: Tuesday, 03-Jul-2007 16:14:08 CEST