This module supports the evaluation of the simulated inelastic scattering data for general prototypes of instruments:
The integral is written by this module to the log file (shown automatically in the Xcontrol window) as "INTEGRAL INTENSITY".
For the simulation of Triple Axis Spectroscopy or
monochromator-analyser backscattering instruments, the user has to scan the
incident and/or scattered neutron wavevectors, and to collect the integral
intensity data for each single point (q,w),
as in real experiments. For this case only the integral written to the log
file is the output of interest, therefore no names for the 'TOF and energy
spectrum files' should be given as an input, in order not to create them .
All other input values or options excepting 'angle' and 'angle range' are
not considered for calculating the "Integral Intensity", i.e. you can give
some dummy values (e.g. 'divide by Bose factor' is not considered although
if it is activated in the GUI).
B.+C. Monochromator + TOF or TOF + Analyser
These two cases comprise direct and inverted geometry instruments in which either the initial or the final average wavelength is selected by a crystal, chopper or other selector system. This wavelength has to be given in the input as "reference wavelength".
1. The input parameters are:
number of bins
[-] |
The number of time and energy channels to be considered; |
primary and secondary flight path
[cm] |
Distance from the moderator to sample and from sample to detector. |
reference wavelength
[Å] |
Initial or final wavelength of the neutrons which is known from the experimental setup. |
time offset
[ms] |
If nonzero, start time at moderator is shifted: TOF' = TOF time offset. |
minimal and maximal time
[ms] |
The TOF range in which the user is interested to bin intensities. |
gradient of timebins
[-] |
Derivative s of the time channel width in function of TOF (as described in the help manual, sec. 4) . |
temperature [K] | Temperature according to the temperature of the sample (only used for the case 'divide by Bose factor'). |
angle and angle range
[-] |
The user can select those neutrons which cross a smaller area on the detector surface by giving the angular position ( 'angle' relative to the X-axis) and width ('angle range') of a window in horizontal direction. In vertical direction no restriction is possible. |
2. Options:
geometry: direct or inverted | Choose geometry type of TOF instrument. |
divide by Bose Factor | Choose whether the energy spectrum shall be normalised or not by the Bose Factor. |
3. Files:
TOF spectrum file | Filename for the TOF spectrum datafile. |
energy spectrum file | Filename for the energy spectrum datafile. |
4. Expressions for TOF binning
For the case of constant channel-width spectra (number of bins: N), the TOF channel boundaries can be calculated in a simple way:
5. Expressions for energy binning
This module also transforms constant angle TOF data into constant angle energy spectra.
Generally in TOF measurements, the total flight time of the neutrons is measured. By knowing the primary, secondary flight path (L1,2) and the average neutron velocity either before (direct geometry) or after (inverted geometry) interacting with the sample, both the primary and secondary TOF can be calculated. The kinetic energies E1,2 before or after the scattering can be calculated from the reference (known) wavelength l (given in Å):
In order to obtain a correct intensity distribution in energy, one has to take into account the derivative resulting from the TOF-energy transformation
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Last modified: Thu Jan 29 15:23:30 MET 2004, G. Zs.Tuesday, 03-Jul-2007 16:14:08 CEST