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PreprocessDetectorsToMD v1¶

../_images/ImageNotFound.png — Enable screenshots using DOCS_SCREENSHOTS in CMake¶

Summary ¶

Its a helper algorithm, used to make common part of transformation from real to reciprocal space. It is used by ConvertToMD v1 and ConvertToMDMinMaxLocal v1 algorithms to save time spent on this transformation when the algorithm used multiple times for multiple measurements on the same instrument.

Properties ¶

Name	Direction	Type	Default	Description
InputWorkspace	Input	MatrixWorkspace	Mandatory	Name of an input Matrix Workspace with instrument.
OutputWorkspace	Output	TableWorkspace		Name of the output Table workspace with pre-processed detectors data. If the workspace exists, it will be replaced.
GetMaskState	Input	boolean	True	Returns masked state of the detectors. If this option is false, the masked detectors are just dropped from the resulting workspace and spectra-to detectors map has to be used to analyse the spectra. This is temporary parameter and logic necessary until Mantid masks signal by 0 rather then NaN.
UpdateMasksInfo	Input	boolean	False	If target workspace already exists as the result of previous deployment of this algorithm, the algorithm just updated masks states column instead of calculating the whole target workspace. The target workspace has to be appropriate for the source workspace This is temporary parameter and logic necessary until Mantid masks signal by 0 rather then NaN.
GetEFixed	Input	boolean	False	This option makes sense for Indirect instrument, where each detector can have its own energy, defined by correspondent crystal-analyzer position. If this option is selected for other instrument types, the value of eFixed is taken from workspace property Ei or eFixed if Ei is missing and is set to NaN if no such properties are defined on the input workspace.

Description ¶

The algorithm calculates expensive part of the transformation from real to reciprocal space, calculating namely, detector positions, sample-detector distances, angular detectors positions, etc. These values can be slow to calculate for composite detectors and other algorithms can substantially benefit from using preprocessed values.

The algorithm places processed values into a table workspace with the following columns:

Column Name :	Type	Description:
DetDirections	V3D	unit 3D vector directed from sample to detector
L2	double	sample-detector distance
TwoTheta	double	Composite detectors Polar angle
Azimuthal	double	Composite detectors Azimutal angle
DetectorID	int	Unique detector number
detIDMap	size_t	index of the detector in the detector’s array
detMask [1]	int	1 if masked and 0 if not
efixed [2]	double	energy of the detector (intirect only)

In addition to the preprocessed detectors intofmation, the following log entries are added to the table workspace:

Ei – Incident neurtorns energy if such log value is attached to input workspace.
L1 – Source-sample distance.
ActualDetectorsNum – total number of existing preprocessed detectors (number of rows in the table above).
InstrumentName – the name of the source instrument.
FakeDetectors – if detectors posisions were not actually preprocessed but fake detectros were used instead
(InstrumentName==*FakeInstrument* in this case).

Notes

Usage ¶

Example - Find min-max values for |Q| transformation :

# Simulates Load of a workspace with all necessary parameters #################
detWS = CreateSimulationWorkspace(Instrument='MAR',BinParams=[-50,5,50],UnitX='DeltaE')
AddSampleLog(detWS,LogName='Ei',LogText='52.',LogType='Number');
#
preprDetWS = PreprocessDetectorsToMD(InputWorkspace=detWS,GetMaskState=1,GetEFixed=1)
# Look at sample results:
print("The resulting table has the following columns:")
print(preprDetWS.keys())
print("The number of rows in the workspace is :  {}".format(len(preprDetWS.column('L2'))))
polar = preprDetWS.column('TwoTheta')
print("The polar angle for detector N {0} is {1:5f} rad".format(10,polar[10]))
print("The table workspace logs (properties) are currently not available from python")

Output:

The resulting table has the following columns:
['DetDirections', 'L2', 'TwoTheta', 'Azimuthal', 'DetectorID', 'detIDMap', 'spec2detMap', 'detMask', 'eFixed', 'DIFA', 'DIFC', 'TZERO']
The number of rows in the workspace is :  918
The polar angle for detector N 10 is 0.314159 rad
The table workspace logs (properties) are currently not available from python

Categories: AlgorithmIndex | MDAlgorithms\Utility