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PolDiffILLReduction dialog.
Table of Contents
Performs polarized diffraction and spectroscopy data reduction for the D7 instrument at the ILL.
| Name | Direction | Type | Default | Description |
|---|---|---|---|---|
| Run | Input | list of str lists | Mandatory | File path of run(s). Allowed values: [‘nxs’] |
| ProcessAs | Input | string | Sample | Choose the process type. Allowed values: [‘Cadmium’, ‘EmptyBeam’, ‘BeamWithCadmium’, ‘Transmission’, ‘Empty’, ‘Quartz’, ‘Vanadium’, ‘Sample’] |
| OutputWorkspace | Output | WorkspaceGroup | Mandatory | The output workspace based on the value of ProcessAs. |
| CadmiumInputWorkspace | Input | WorkspaceGroup | The name of the cadmium workspace group. | |
| BeamInputWorkspace | Input | MatrixWorkspace | The name of the empty beam input workspace. | |
| CadmiumTransmissionInputWorkspace | Input | MatrixWorkspace | The name of the cadmium transmission input workspace. | |
| TransmissionInputWorkspace | Input | MatrixWorkspace | The name of the transmission input workspace. | |
| EmptyInputWorkspace | Input | WorkspaceGroup | The name of the empty (container) workspace. | |
| QuartzInputWorkspace | Input | WorkspaceGroup | The name of the polarisation efficiency correction workspace. | |
| OutputTreatment | Input | string | Individual | Which treatment of the provided scan should be used to create output. Allowed values: [‘Individual’, ‘Average’, ‘Sum’] |
| ClearCache | Input | boolean | True | Whether or not to clear the cache of intermediate workspaces. |
| AbsoluteNormalisation | Input | boolean | True | Whether or not to perform normalisation to absolute units. |
| SelfAttenuationMethod | Input | string | None | Which approach to calculate (or not) the self-attenuation correction factors to be used. Allowed values: [‘None’, ‘Numerical’, ‘MonteCarlo’, ‘User’] |
| SampleGeometry | Input | string | None | Sample geometry for self-attenuation correction to be applied. Allowed values: [‘None’, ‘FlatPlate’, ‘Cylinder’, ‘Annulus’, ‘Custom’] |
| SampleAndEnvironmentProperties | Input | Dictionary | dict() | Dictionary for the information about sample and its environment. |
| SampleSelfAttenuationFactors | Input | WorkspaceGroup | The name of the workspace group containing self-attenuation factors of the sample. | |
| ScatteringAngleBinSize | Input | number | 0.5 | Scattering angle bin size in degrees used for expressing scan data on a single TwoTheta axis. |
| InstrumentCalibration | Input | string | The path to the calibrated Instrument Parameter File. Allowed extensions: [‘.xml’] |
This algorithm performs polarised diffraction reduction for the D7 instrument at the ILL. With each call, this algorithm processes one type of data which is a part of the whole experiment. The logic is resolved by the property ProcessAs, which governs the reduction steps based on the requested type. It can be one of the 8: cadmium, empty beam, beam-with-cadmium, transmission, empty, quartz, vanadium, and sample. The full data treatment of the complete experiment should be build up as a chain with multiple calls of this algorithm over various types of acquisitions. The sequence should be logical, typically as enumerated above, since the later processes need the outputs of earlier processes as input. The common mandatory input is a run file (numor), or a list of them. In case a list is provided, coming for example from a scan over twoTheta angle, the data is treated individually up to the point of background subtraction, and then can be either left as a list, each detector can averaged over the scan, or all data from the scan can summed.
Most of the corrections, such as background subtraction or polarisation correction, are optional and their inclusion depends on the provided inputs and set flags. However, it is mandatory to provide basic information about the vanadium and sample, such as mass, chemical formula, and either density or number density.
The common mandatory output is a workspace, but up to which step it is processed, depends on ProcessAs.
Different input properties can be specified depending on the value of ProcessAs, as summarized in the table:
| ProcessAs | Input Workspace Properties | Other Input Properties |
|---|---|---|
| BeamWithCadmium | ||
| EmptyBeam |
|
|
| Transmission |
|
|
| Cadmium | ||
| Empty | ||
| Quartz |
|
|
| Vanadium |
|
|
| Sample |
|
|
All the input workspace properties above are optional, unless bolded. For example, if processing as sample, if a empty container and cadmium absorber inputs are specified, subtraction will be performed, if not, the step will be skipped. The rare exceptions are when processing as transmission, when beam input workspace is mandatory, and to calculate polarising efficiencies, where input from transmission is indispensable.
This property is a dictionary containing all of the information about the sample and its environment. This information is used in self-attenuation calculations and in normalisation.
The complete list of keys can is summarised below:
Sample-only keys:
The SampleMass needs to be defined, as well as FormulaUnitMass and FormulaUnits, even when the self-attenuation is not taken into account. The other parameters are required when the self-attenuation is calculated.
Container-only keys:
Beam-only keys:
These do not have to be defined, and by default will be set to be larger than the sample size.
Then, depending on the chosen sample geometry, additional parameters need to be defined:
Optional keys:
In the flowcharts below the yellow ovals represent the inputs, the grey parallelograms are the outputs for each process type.
Full treatment is built by stacking up unary reductions with corresponding ProcessAs. The diagram below illustrates the flow of processing. Letters denote beam with absorber (AT), beam (B), transmission (T), cadmium (A), empty (C), quartz (Q), vanadium (V), sample (S). AT is processed first, and passed to all the other processes. B takes only AT as optional input, and the output of B is needed by all transmisison calculations. T takes AT and B as inputs, and the calculated transmission is used by Q, V, and S respectively. C and A are supplied to Q, V, and S respectively. Q takes A, C, its T, and the output is provided to V and S. V takes A, C, its T, and Q as inputs and the output can used to normalise S S takes A, C, its T, as well as Q as inputs. The output of S is reduced sample in desired units.
This example below performs a complete reduction for D7 data.
Note
For transmission calculation, the beam run and the transmission run have to be recorded at the same instrument configuration. For container subtraction, the container and the sample run have to be recorded at the same configuration.
Note
To run these usage examples please first download the usage data, and add these to your path. In Mantid this is done using Manage User Directories.
Example - full treatment of a sample
vanadium_dictionary = {'SampleMass':8.54,'SampleDensity':0.2,'FormulaUnits':1,'FormulaUnitMass':50.94}
sample_dictionary = {'SampleMass':2.932,'SampleDensity':0.1,'FormulaUnits':1, 'FormulaUnitMass':182.56}
# Beam with cadmium absorber, used for transmission
PolDiffILLReduction(
Run='396991',
OutputWorkspace='cadmium_transmission_ws',
ProcessAs='BeamWithCadmium'
)
# Beam measurement for transmisison
PolDiffILLReduction(
Run='396983',
OutputWorkspace='beam_ws',
CadmiumTransmissionInputWorkspace='cadmium_transmission_ws_1',
ProcessAs='EmptyBeam'
)
print('Cadmium absorber transmission is {0:.3f}'.format(mtd['cadmium_transmission_ws_1'].readY(0)[0] / mtd['beam_ws_1'].readY(0)[0]))
# Quartz transmission
PolDiffILLReduction(
Run='396985',
OutputWorkspace='quartz_transmission',
CadmiumTransmissionInputWorkspace='cadmium_transmission_ws_1',
BeamInputWorkspace='beam_ws_1',
ProcessAs='Transmission'
)
print('Quartz transmission is {0:.3f}'.format(mtd['quartz_transmission_1'].readY(0)[0]))
# Empty container
PolDiffILLReduction(
Run='396917',
OutputWorkspace='empty_ws',
ProcessAs='Empty'
)
# Cadmium absorber
PolDiffILLReduction(
Run='396928',
OutputWorkspace='cadmium_ws',
ProcessAs='Cadmium'
)
# Polarisation correction
PolDiffILLReduction(
Run='396939',
OutputWorkspace='pol_corrections',
CadmiumInputWorkspace='cadmium_ws',
EmptyInputWorkspace='empty_ws',
TransmissionInputWorkspace='quartz_transmission_1',
OutputTreatment='Average',
ProcessAs='Quartz'
)
# Vanadium transmission
PolDiffILLReduction(
Run='396990',
OutputWorkspace='vanadium_transmission',
CadmiumTransmissionInputWorkspace='cadmium_transmission_ws_1',
BeamInputWorkspace='beam_ws_1',
ProcessAs='Transmission'
)
print('Vanadium transmission is {0:.3f}'.format(mtd['vanadium_transmission_1'].readY(0)[0]))
# Vanadium reduction
PolDiffILLReduction(
Run='396993',
OutputWorkspace='vanadium_ws',
CadmiumInputWorkspace='cadmium_ws',
EmptyInputWorkspace='empty_ws',
TransmissionInputWorkspace='vanadium_transmission_1',
QuartzInputWorkspace='pol_corrections',
OutputTreatment='Sum',
SampleGeometry='None',
SampleAndEnvironmentProperties=vanadium_dictionary,
ProcessAs='Vanadium'
)
# Sample transmission
PolDiffILLReduction(
Run='396986',
OutputWorkspace='sample_transmission',
CadmiumTransmissionInputWorkspace='cadmium_transmission_ws_1',
BeamInputWorkspace='beam_ws_1',
ProcessAs='Transmission'
)
print('Sample transmission is {0:.3f}'.format(mtd['sample_transmission_1'].readY(0)[0]))
# Sample reduction
PolDiffILLReduction(
Run='397004',
OutputWorkspace='sample_ws',
CadmiumInputWorkspace='cadmium_ws',
EmptyInputWorkspace='empty_ws',
TransmissionInputWorkspace='sample_transmission_1',
QuartzInputWorkspace='pol_corrections',
OutputTreatment='Individual',
SampleGeometry='None',
SampleAndEnvironmentProperties=sample_dictionary,
ProcessAs='Sample'
)
Output:
Cadmium absorber transmission is 0.011
Quartz transmission is 0.700
Vanadium transmission is 0.886
Sample transmission is 0.962
Categories: AlgorithmIndex | ILL\Diffraction
Python: PolDiffILLReduction.py (last modified: 2021-04-30)