TransformToIqt v1¶
Summary¶
Transforms an inelastic reduction to I(Q, t)
Properties¶
Name |
Direction |
Type |
Default |
Description |
---|---|---|---|---|
SampleWorkspace |
Input |
Mandatory |
Name for the sample workspace. |
|
ResolutionWorkspace |
Input |
Mandatory |
Name for the resolution workspace. |
|
EnergyMin |
Input |
number |
-0.5 |
Minimum energy for fit. |
EnergyMax |
Input |
number |
0.5 |
Maximum energy for fit. |
BinReductionFactor |
Input |
number |
10 |
Decrease total number of spectrum points by this ratio through merging of intensities from neighbouring bins. |
NumberOfIterations |
Input |
number |
50 |
Number of randomised simulations for monte-carlo error calculation. |
SeedValue |
Input |
number |
89631139 |
Seed for pseudo-random number generator in monte-carlo error calculation. |
ParameterWorkspace |
Output |
Table workspace for saving TransformToIqt properties |
||
OutputWorkspace |
Output |
Output workspace |
||
DryRun |
Input |
boolean |
False |
Only calculate and output the parameters |
CalculateErrors |
Input |
boolean |
True |
Calculate monte-carlo errors. |
EnforceNormalization |
Input |
boolean |
True |
Normalization to enforce I(t=0) |
Description¶
This algorithm transforms either a reduced (_red) or S(Q, w) (_sqw) workspace to a I(Q, t) workspace.
Theory¶
The measured spectrum
In general, the origin in energy for the sample run and the resolution run need
not necessarily be the same or indeed be exactly zero in the conversion of the
RAW data from time-of-flight to energy transfer. This will depend, for example,
on the sample and vanadium shapes and positions and whether the analyser
temperature has changed between the runs. The procedure takes this into account
automatically, without using an arbitrary fitting procedure, in the following
way. From the general properties of the FT, the transform of an offset
Lorentzian has the form
The interpretation of the data must also take into account the propagation of
statistical errors (counting statistics) in the measured data as discussed by
Wild et al [1]. If the count in channel
Note that
References¶
U P Wild, R Holzwarth & H P Good, Rev Sci Instr 48 1621 (1977)
Workflow¶
By default, the above workflow is executed. If EnforceNormalization is set to False, the LHSWorkspace from the output from ExtractFFTSpectrum v1 is used in both branches to perform the final workspace division and the two intermediate workspace divisions are skipped.
Usage¶
Example - TransformToIqt with IRIS data.
sample = Load('irs26176_graphite002_red.nxs')
can = Load('irs26173_graphite002_red.nxs')
params, iqt = TransformToIqt(SampleWorkspace=sample,
ResolutionWorkspace=can,
EnergyMin=-0.5,
EnergyMax=0.5,
BinReductionFactor=10,
EnableLogging=True)
print('Number of output bins: %d' % (params.cell('SampleOutputBins', 0)))
print('Resolution bins: %d' % (params.cell('ResolutionBins', 0)))
Output:
Number of output bins: 172
Resolution bins: 6
Categories: AlgorithmIndex | Workflow\Inelastic | Workflow\MIDAS
Source¶
Python: TransformToIqt.py