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PowderReduceP2D v1

Summary

The algorithm used to process the results of powder diffraction experiments and create a ‘.p2d’ file for multidimensional Rietveld refinement.

See Also

SaveP2D, Bin2DPowderDiffraction

Properties

Name

Direction

Type

Default

Description

SampleData

Input

string

Datafile that should be used.

DoIntensityCorrection

Input

boolean

False

If set to True you have to declare a vanadium measurement for intensity correction.

VanaData

Input

string

Vanadium measurement for intensity correction.

DoVanaBackgroundCorrection

Input

boolean

False

If set to True you have to declare an empty can measurement for vanadium background correction.

VanaEmpty

Input

string

Empty measurement for vanadium data.

DoBackgroundCorrection

Input

boolean

False

If set to True you have to declare an empty can measurement for background correction.

EmptyData

Input

string

Empty measurement of the can for background correction.

CalFile

Input

string

Calibration file.

DoEdgebinning

Input

boolean

False

If set to True you have to declare a BinEdges file.

BinEdgesFile

Input

string

BinEdges file used for edgebinning.

OutputFile

Input

string

Mandatory

Output File for p2d Data.

SystemTest

Input

boolean

False

Set to True if running a system test. Greatly decreases the amount of data used.

TwoThetaMin

Input

number

50

Minimum value for 2 Theta. Everything smaller gets removed.

TwoThetaMax

Input

number

120

Maximum value for 2 Theta. Everything bigger gets removed.

LambdaMin

Input

number

0.3

Minimum value for lambda. Everything smaller gets removed. If zero it is not used and values get calculated from center wavelength.

LambdaMax

Input

number

1.1

Maximum value for lambda. Everything bigger gets removed. If zero it is not used and values get calculated from center wavelength.

DMin

Input

number

0.11

Minimum value for d. Everything smaller gets removed. If zero it is not used and values get calculated from 2 theta and lambda.

DMax

Input

number

1.37

Maximum value for d. Everything bigger gets removed. If zero it is not used and values get calculated from 2 theta and lambda.

DpMin

Input

number

0.48

Minimum value for dp. Everything smaller gets removed. If zero it is not used and values get calculated from 2 theta and lambda.

DpMax

Input

number

1.76

Maximum value for dp. Everything bigger gets removed. If zero it is not used and values get calculated from 2 theta and lambda.

Maskfile

Input

string

Maskfile that should be used. If specified, an Instrument has to be given as well.

Instrument

Input

string

Instrument used. Only needs to be specified if an Maskfile is specified.

ReturnLinearRanges

Input

boolean

False

if set to true, the algorithm would return linear detector’s ranges (dx,dy) rather then angular ranges (dAzimuthal,dPolar)

ParFile

Input

string

not_used.par

An optional file that contains of the list of angular parameters for the detectors and detectors groups; If specified, will use data from file instead of the data, calculated from the instument description. Allowed extensions: [‘.par’, ‘.phx’]

OutputParTable

Input

string

Detec

If not empty, a name of a table workspace which will contain the calculated par or phx values for the detectors.

LowerCutoff

Input

number

99.998

The percentage of the average to use as the lower bound.

Width

Input

number

150

The width of the time of flight (in microseconds) to remove from the data.

Frequency

Input

number

Optional

The frequency of the source (in Hz) used to calculate the minimum time of flight to filter.

WorkspaceName

Input

string

POWTEX

The base of the output workspace names. Names will have _group, _cal, _mask appended to them.

InstrumentName

Input

string

Optional: Name of the instrument on which to base the GroupingWorkspace.

InstrumentFilename

Input

string

Optional: Path to a file (full or relative) defining the instrument on which to base the GroupingWorkspace. The file could be an IDF or a NeXus Geometry file. Note, InstrumentFilename or InstrumentName must be specified, but not both. Allowed extensions: [‘.xml’, ‘.hdf5’, ‘.nxs’, ‘.nxs.h5’]

MakeGroupingWorkspace

Input

boolean

True

Set to true to create a GroupingWorkspace with called WorkspaceName_group.

MakeCalWorkspace

Input

boolean

True

Set to true to create a CalibrationWorkspace with called WorkspaceName_cal.

MakeMaskWorkspace

Input

boolean

True

Set to true to create a MaskWorkspace with called WorkspaceName_mask.

TofMin

Input

number

0

Minimum for TOF axis. Defaults to 0.

TofMax

Input

number

Optional

Maximum for TOF axis. Defaults to Unused.

FixConversionIssues

Input

boolean

True

Set DIFA and TZERO to zero if there is an error and the pixel is masked

MaskedWorkspace

Input

string

POWTEX_mask

If given but not as a SpecialWorkspace2D, the masking from this workspace will be copied. If given as a SpecialWorkspace2D, the masking is read from its Y values.

SpectraList

Input

int list

A list of spectra to mask

DetectorList

Input

int list

A list of detector ID’s to mask

WorkspaceIndexList

Input

unsigned int list

A list of the workspace indices to mask

ForceInstrumentMasking

Input

boolean

False

Works when ‘MaskedWorkspace’ is provided and forces to use spectra-detector mapping even in case when number of spectra in ‘Workspace’ and ‘MaskedWorkspace’ are equal

StartWorkspaceIndex

Input

number

0

If other masks fields are provided, it’s the first index of the target workspace to be allowed to be masked from by these masks, if not, its the first index of the target workspace to mask. Default value is 0 if other masking is present or ignored if not.

EndWorkspaceIndex

Input

number

Optional

If other masks are provided, it’s the last index of the target workspace allowed to be masked to by these masks, if not, its the last index of the target workspace to mask. Default is number of histograms in target workspace if other masks are present or ignored if not.

ComponentList

Input

str list

A list names of components to mask

AttenuationXSection

Input

number

5.08

The ABSORPTION cross-section, at 1.8 Angstroms, for the sample material in barns. Column 8 of a table generated from http://www.ncnr.nist.gov/resources/n-lengths/.

ScatteringXSection

Input

number

5.1

The (coherent + incoherent) scattering cross-section for the sample material in barns. Column 7 of a table generated from http://www.ncnr.nist.gov/resources/n-lengths/.

SampleNumberDensity

Input

number

0.07192

The number density of the sample in number of atoms per cubic angstrom if not set with SetSampleMaterial.

CylinderSampleHeight

Input

number

4

The height of the cylindrical sample in centimetres.

CylinderSampleRadius

Input

number

0.4

The radius of the cylindrical sample in centimetres.

NumberOfSlices

Input

number

10

The number of slices into which the cylinder is divided for the calculation.

NumberOfAnnuli

Input

number

10

The number of annuli into which each slice is divided for the calculation.

ScatterFrom

Input

string

Sample

The component to calculate the absorption for (default: Sample). Allowed values: [‘Sample’, ‘Container’, ‘Environment’]

NumberOfWavelengthPoints

Input

number

Optional

The number of wavelength points for which the numerical integral is calculated (default: all points)

ExpMethod

Input

string

Normal

Select the method to use to calculate exponentials, normal or a fast approximation (default: Normal). Allowed values: [‘Normal’, ‘FastApprox’]

EMode

Input

string

Elastic

The energy mode (default: elastic). Allowed values: [‘Elastic’, ‘Direct’, ‘Indirect’]

EFixed

Input

number

0

The value of the initial or final energy, as appropriate, in meV. Will be taken from the instrument definition file, if available.

CylinderAxis

Input

dbl list

0,1,0

A 3D vector specifying the cylindrical sample’s orientation

dSpaceBinning

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.

dPerpendicularBinning

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.

NormalizeByBinArea

Input

boolean

False

Normalize the binned workspace by the bin area.

FWHM

Input

number

2

The number of points covered, on average, by the fwhm of a peak. Passed through to FindPeaks. Default 7.

Tolerance

Input

number

2

A measure of the strictness desired in meeting the condition on peak candidates. Passed through to FindPeaks.Default 4.

PeakPositionTolerance

Input

number

0.05

Tolerance on the found peaks positions against the input peak positions. A non-positive value turns this option off.

BackgroundType

Input

string

Quadratic

The type of background of the histogram. Allowed values: Linear, Quadratic

HighBackground

Input

boolean

True

Flag whether the input data has high background compared to peak heights.

WorkspaceIndex

Input

number

Optional

If set, will remove peaks only in the given spectrum of the workspace. Otherwise, all spectra will be searched.

Filter

Input

string

Butterworth

The type of the applied filter. Allowed values: [Zeroing, Butterworth]

Params

Input

string

20,2

The filter parameters: For Zeroing, 1 parameter: n - an integer greater than 1 meaning that the Fourier coefficientswith frequencies outside the 1/n of the original range will be set to zero. For Butterworth, 2 parameters: n and order, giving the 1/n truncation and the smoothing order.

IgnoreXBins

Input

boolean

True

Ignores the requirement that X bins be linear and of the same size. Set this to true if you are using log binning.The output X axis will be the same as the input either way.

AllSpectra

Input

boolean

True

Smooth all spectra.

WorkspaceIndexSmooth

Input

number

0

Workspace index for smoothing

AddMinimum

Input

boolean

True

If set to True, adds the most negative intensity to all intensities.

ResetValue

Input

number

0

Set negative intensities to the specified value (default=0).

AddMinimumVana

Input

boolean

True

If set to True, adds the most negative intensity to all intensities.

ResetValueVana

Input

number

1

Set negative intensities to the specified value (default=1).

Description

Input

This algorithm can be used for one run of sample data. For correction and background reduction additional measurements of Vanadium(VanaData) and an empty can(EmptyData) can be specified but are not necessary. If an empty measurement is specified, it is substracted from the sample measurement. If a Vanadium measurement is specified, the sample measurement is divided by the vanadium measurement. If either or both are not specified these steps are skipped. It is highly recommended to specify both. Additionally, an empty vanadium measurement can be supplied.

Calibration, Grouping, Masking

The calibration is done using the Calibration File(CalFile). Additionally three implicit workspaces (<instrument>_group, <instrument>_cal, <instrument>_mask) are created during the algorithms execution if they do not exist already. Masking can be applied by an xml file as well.

Binning

The recommended binning (edgebinning) requires an edgebinning file to be specified. If no edgebinning file is specified, logarithmic binning (standard values: x1=-0.008, x2=0.01) is used.

Manipulating data with constants

The reduced data are checked for negative intensities. If any are found, they are removed either by adding the most negative valueor by setting the intensity to a specified value. This is done, because negative values cannot be processed in multidimensional Rietveld refinement.

Output

The output of this Workflow algorithm is a p2d file. The p2d file contains values for 2Theta and lambda (columns 1 and 2) as well as d and dperp (columns 3 and 4). Column 5 contains the intensity data.

Workflow

../_images/PowderReduceP2D.svg ../_images/PowderReduceP2D_ProcessSampleRun.svg ../_images/PowderReduceP2D_ProcessCanRun.svg ../_images/PowderReduceP2D_ProcessVanadiumRun.svg

Usage

This is a workflow algorithm to process the results of powder diffraction experiments and create a p2d file for multidimensional Rietveld refinement. The algorithm is currently tested for the Instruments POWGEN, SNAP and PTXatPG3 (POWTEX detector at POWGEN instrument).

Categories: AlgorithmIndex | Diffraction\Reduction

Source

Python: PowderReduceP2D.py