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SofQWCentre v1

Summary

Converts a 2D workspace that has axes in units of DeltaE (energy transfer) against spectrum number to one that gives intensity as a function of DeltaE against momentum transfer

See Also

SofQW, Rebin2D

Properties

Name	Direction	Type	Default	Description
InputWorkspace	Input	MatrixWorkspace	Mandatory	Reduced data in units of energy transfer DeltaE. The workspace must contain histogram data and have common bins across all spectra.
OutputWorkspace	Output	MatrixWorkspace	Mandatory	The name to use for the q-omega workspace.
QAxisBinning	Input	dbl list	Mandatory	The bin parameters to use for the q axis (in the format used by the Rebin v1 algorithm).
EMode	Input	string	Mandatory	The energy transfer analysis mode (Direct/Indirect). Allowed values: [‘Direct’, ‘Indirect’]
EFixed	Input	number	0	The value of fixed energy: $E_i$ (EMode=Direct) or $E_f$ (EMode=Indirect) (meV). Must be set here if not available in the instrument definition.
ReplaceNaNs	Input	boolean	False	If true, all NaN values in the output workspace are replaced using the ReplaceSpecialValues algorithm.
EAxisBinning	Input	dbl list		The bin parameters to use for the E axis (optional, in the format used by the Rebin v1 algorithm).
DetectorTwoThetaRanges	Input	TableWorkspace		A table workspace use by SofQWNormalisedPolygon containing a ‘Detector ID’ column as well as ‘Min two theta’ and ‘Max two theta’ columns listing the detector’s min and max scattering angles in radians.

Description

This algorithm is for use by inelastic instruments and takes as its input a workspace where the data’s been reduced to be in units of energy transfer against spectrum number (which can be seen as equivalent to angle, with the angle being taken from the detector(s) to which the spectrum pertains). For each detector the value of momentum transfer ($Q$) is calculated, and the counts for detectors and each input energy transfer bin are added to the appropriate output $(Q;\mathrm{\Delta }E)$ bin.

The momentum transfer ($Q$-values) obtained for each detector are calculated for the detector center, so the binning algorithm uses center-point binning. This algorithm does not use the DetectorTwoThetaRanges optional input property for the $Q$ calculation. Use SofQWPolygon v1 and SofQWNormalisedPolygon v1 for more complex and precise (but slower) binning strategies.

The energy binning will not be changed by this algorithm, so the input workspace should already have the desired bins (though this axis can be rebinned afterwards if desired). The EMode and EFixed parameters are used for the calculation of $Q$.

If the input workspace is a distribution (i.e. counts/meV ) then the output workspace will similarly be divided by the bin width in both directions (i.e. will contain counts/meV/(1/Angstrom) ).

Usage

Example - simple transformation of inelastic workspace:

# create sample inelastic workspace for MARI instrument containing 1 at all spectra values
ws=CreateSimulationWorkspace(Instrument='MAR',BinParams='-10,1,10')
# convert workspace into MD workspace
ws=SofQWCentre(InputWorkspace=ws,QAxisBinning='-3,0.1,3',Emode='Direct',EFixed=12)

print("The converted X values are:")
print(ws.readX(59)[0:10])
print(ws.readX(59)[10:21])

print("The converted Y values are:")
print(ws.readY(59)[0:10])
print(ws.readY(59)[10:21])

Output:

The converted X values are:
[-10.  -9.  -8.  -7.  -6.  -5.  -4.  -3.  -2.  -1.]
[  0.   1.   2.   3.   4.   5.   6.   7.   8.   9.  10.]
The converted Y values are:
[ 12.  18.  18.  18.  18.  21.  18.  18.  21.  12.]
[ 18.  21.  24.  24.  24.  21.  24.  33.  39.  45.]

Categories: AlgorithmIndex | Inelastic\SofQW

Source

C++ header: SofQWCentre.h

C++ source: SofQWCentre.cpp