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AlignAndFocusPowder v1

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Summary

Algorithm to focus powder diffraction data into a number of histograms according to a grouping scheme defined in a CalFile.

See Also

AlignAndFocusPowderFromFiles

Properties

Name	Direction	Type	Default	Description
InputWorkspace	Input	MatrixWorkspace	Mandatory	The input workspace
OutputWorkspace	Output	MatrixWorkspace	Mandatory	The result of diffraction focussing of InputWorkspace
UnfocussedWorkspace	Output	MatrixWorkspace		Treated data in d-spacing before focussing (optional). This will likely need rebinning.
CalFileName	Input	string		The name of the calibration file with offset, masking, and grouping data. Allowed extensions: [‘.h5’, ‘.hd5’, ‘.hdf’, ‘.cal’]
GroupFilename	Input	string		Overrides grouping from CalFileName. Allowed extensions: [‘.xml’, ‘.cal’]
GroupingWorkspace	InOut	GroupingWorkspace		Optional: A GroupingWorkspace giving the grouping info.
CalibrationWorkspace	InOut	TableWorkspace		Optional: A Workspace containing the calibration information. Either this or CalibrationFile needs to be specified.
OffsetsWorkspace	Input	OffsetsWorkspace		Optional: An OffsetsWorkspace giving the detector calibration values.
MaskWorkspace	InOut	MaskWorkspace		Optional: A workspace giving which detectors are masked.
MaskBinTable	Input	TableWorkspace		Optional: A workspace giving pixels and bins to mask.
Params	Input	dbl list		A comma separated list of first bin boundary, width, last bin boundary. Optionally this can be followed by a comma and more widths and last boundary pairs. Negative width values indicate logarithmic binning.
ResampleX	Input	number	0	Number of bins in x-axis. Non-zero value overrides “Params” property. Negative value means logarithmic binning.
Dspacing	Input	boolean	True	Bin in Dspace. (True is Dspace; False is TOF)
DMin	Input	dbl list		Minimum for Dspace axis. (Default 0.)
DMax	Input	dbl list		Maximum for Dspace axis. (Default 0.)
DeltaRagged	Input	dbl list		Step parameter for rebin
TMin	Input	number	Optional	Minimum for TOF axis. Defaults to 0.
TMax	Input	number	Optional	Maximum for TOF or dspace axis. Defaults to 0.
PreserveEvents	Input	boolean	True	If the InputWorkspace is an EventWorkspace, this will preserve the full event list (warning: this will use much more memory!).
RemovePromptPulseWidth	Input	number	0	Width of events (in microseconds) near the prompt pulse to remove. 0 disables
ResonanceFilterUnits	Input	string	Wavelength	Units for resonances to be filtered in. The data will be converted to these units temporarily to filter. Allowed values: [‘Energy’, ‘Wavelength’]
ResonanceFilterLowerLimits	Input	dbl list		Minimum values to filter absorption resonance. This must have same number of values as ResonanceFilterUpperLimits. Default behavior is to not filter.
ResonanceFilterUpperLimits	Input	dbl list		Maximum values to filter absorption resonance. This must have same number of values as ResonanceFilterLowerLimits. Default behavior is to not filter.
CompressTolerance	Input	number	1e-05	Compress events (in microseconds) within this tolerance. (Default 1e-5)
CompressWallClockTolerance	Input	number	Optional	The tolerance (in seconds) on the wall-clock time for comparison. Unset means compressing all wall-clock times together disabling pulsetime resolution.
CompressStartTime	Input	string		An ISO formatted date/time string specifying the timestamp for starting filtering. Ignored if WallClockTolerance is not specified. Default is start of run
LorentzCorrection	Input	boolean	False	Multiply each spectrum by sin(theta) where theta is half of the Bragg angle
UnwrapRef	Input	number	0	Reference total flight path for frame unwrapping. Zero skips the correction
LowResRef	Input	number	0	Reference DIFC for resolution removal. Zero skips the correction
CropWavelengthMin	Input	number	0	Crop the data at this minimum wavelength. Overrides LowResRef.
CropWavelengthMax	Input	number	Optional	Crop the data at this maximum wavelength. Forces use of CropWavelengthMin.
PrimaryFlightPath	Input	number	-1	If positive, focus positions are changed. (Default -1)
SpectrumIDs	Input	int list		Optional: Spectrum Nos (note that it is not detector ID or workspace indices).
L2	Input	dbl list		Optional: Secondary flight (L2) paths for each detector
Polar	Input	dbl list		Optional: Polar angles (two thetas) for detectors
Azimuthal	Input	dbl list		Azimuthal angles (out-of-plain) for detectors
LowResSpectrumOffset	Input	number	-1	Offset on spectrum No of low resolution spectra from high resolution one. If negative, then all the low resolution TOF will not be processed. Otherwise, low resolution TOF will be stored in an additional set of spectra. If offset is equal to 0, then the low resolution will have same spectrum Nos as the normal ones. Otherwise, the low resolution spectra will have spectrum IDs offset from normal ones.
ReductionProperties	Input	string	__powdereduction

Description

This is a workflow algorithm that does the bulk of the work for time focusing diffraction data. This is done by executing several sub-algorithms as listed below. The way that algorithms are connected together is better described in the workflow diagram

• ApplyDiffCal v1

• CompressEvents v1 (event workspace only)

• ConvertDiffCal v1 to convert legacy offsets workspace to difcal table

• ConvertUnits v1

• DiffractionFocussing v2

• EditInstrumentGeometry v1

• LoadDetectorsGroupingFile v1 when grouping file is specified without a calibration file

• LoadDiffCal v1

• AppendSpectra v1 only used when LowResRef is specified

• LorentzCorrection v1

• MaskBins v1 for filtering out absorption resonances

• MaskBinsFromTable v1 for filtering out single crystal peaks from powder data

• MaskDetectors v1

• Rebin v1

• ResampleX v1

• RebinRagged v1

• RemoveLowResTOF v1 CropWavelengthMin and CropWavelengthMax are prefered

• RemovePromptPulse v1

• SortEvents v1 (event workspace only)

• UnwrapSNS v1

Workflow

The main workflow of the algorithm can be described in following diagram. In this diagram, the CalibrationWorkspace, MaskWorkspace, and GroupingWorkspace are abstractions of the many ways that this information can be provided (see below).

diagram generation was disabled

Calibration

The way that calibration is supplied can be confusing. This section will attempt to clarify it.

Workspaces provided: If the GroupingWorkspace, CalibrationWorkspace, or MaskWorkspace are supplied as parameters they are used. If the OffsetsWorkspace is supplied it is converted to a CalibrationWorkspace using ConvertDiffCal v1. The values of CalFileName and GroupFilename will be ignored

Filenames provided, Workspaces not: Assuming the instrument short-name is <INSTR> (replace with the actual instrument short-name), the algorithm will look for the workspaces <INSTR>_group, <INSTR>_cal (falling back to <INSTR>_offsets), and <INSTR>_mask and use them without consulting the files. This behavior is to reduce the amount of overhead in processing a collection of input data. When loading information from a file, all 3 workspaces can be read from either type of calibration file (.h5 or .cal) and will get the default names. If the GroupFilename is provided, that will override the grouping information in the CalFilename.

Note

If the user wishes to force reading the supplied calibration file(s), they must delete the workspaces <INSTR>_group, <INSTR>_cal, <INSTR>_offsets, and <INSTR>_mask.

Usage

Example: A simple Powgen example

The files needed for this example are not present in our standard usage data download due to their size. They can however be downloaded using these links: PG3_9830_event.nxs and pg3_mantid_det.cal.

You will have to rename pg3_mantid_det.cal manually, as its name in the link above is a list of random characters.

PG3_9830_event = Load('PG3_9830_event.nxs')
PG3_9830_event = AlignAndFocusPowder(PG3_9830_event,
                                     CalFileName='pg3_mantid_det.cal', Params='100')

Categories: AlgorithmIndex | Workflow\Diffraction

Source

C++ header: AlignAndFocusPowder.h

C++ source: AlignAndFocusPowder.cpp