3.13

ReflectometryILLSumForeground v1

../_images/ReflectometryILLSumForeground-v1_dlg.png

ReflectometryILLSumForeground dialog.

Summary

Sums foreground pixels in selected summation mode, optionally converting to reflectivity.

Properties

Name Direction Type Default Description
InputWorkspace Input MatrixWorkspace Mandatory An input workspace (units wavelength) to be integrated.
OutputWorkspace Output MatrixWorkspace Mandatory The integrated foreground divided by the summed direct beam.
SubalgorithmLogging Input string Logging OFF Enable or disable child algorithm logging. Allowed values: [‘Logging OFF’, ‘Logging ON’]
Cleanup Input string Cleanup ON Enable or disable intermediate workspace cleanup. Allowed values: [‘Cleanup ON’, ‘Cleanup OFF’]
SummationType Input string SumInLambda Type of summation to perform. Allowed values: [‘SumInLambda’, ‘SumInQ’]
FlatSample Input string Flat Sample For SumInQ option, determines if the summation should be done for a flat or bent sample. Allowed values: [‘Flat Sample’, ‘Bent Sample’]
DirectForegroundWorkspace Input MatrixWorkspace   Summed direct beam workspace if output in reflectivity is required.
Foreground Input int list 2147483647,2147483647,2147483647 A three element array of foreground start, centre and end workspace indices.
WavelengthRange Input dbl list 0 The wavelength bounds when summing in Q.

Description

This algorithm is typically the second step in the reflectometry reduction workflow. It consumes the output of ReflectometryILLPreprocess, producing

  • the summed foreground if only InputWorkspace is given. This should be used for the direct beam.
  • the reflectivity if both InputWorkspace and DirectForegroundWorkspace are given. DirectForegroundWorkspace should be the output of the above case, i.e. the summed direct foreground.

The reflectivity output of this algorithm can be forwarded to ReflectometryILLConvertToQ or, in case of polarization analysis, ReflectometryILLPolarizationCor.

The following diagram gives an overview of the algorithm:

../_images/ReflectometryILLSumForeground-v1_wkflw.png

Summation type

The SummationType property controls how the foreground pixels are summed.

SumInLambda
extracts the centre pixel histogram using ExtractSingleSpectrum and adds the intensities of the rest of the foreground pixels. Errors are summed in squares. The summed data is subsequently divided by the direct beam.
SumInQ
sums the pixels using ReflectometrySumInQ. Before summation, the data is divided by the direct beam.

Foreground pixels

If InputWorkspace has been processed by ReflectometryILLPreprocess, the foreground information is available in the sample logs under the entries starting with foreground.. By default these are used automatically.

The sample logs can be overriden using the Foreground property. It is a list of three integers defining the range and centre pixels as workspace indices: [start, centre, end]. The start and end values are inclusive.

Usage

Note

To run these usage examples please first download the usage data, and add these to your path. In MantidPlot this is done using Manage User Directories.

Example - Sum in wavelength

# Use same foreground and background settings for direct and reflected
# beams.
# Python dictionaries can be passed to algorithms as 'keyword arguments'.
settings = {
    'ForegroundHalfWidth':[5],
    'LowAngleBkgOffset': 10,
    'LowAngleBkgWidth': 20,
    'HighAngleBkgOffset': 10,
    'HighAngleBkgWidth': 50,
}

# Direct beam
direct = ReflectometryILLPreprocess(
    Run='ILL/D17/317369.nxs',
    OutputBeamPositionWorkspace='direct_beam_pos',  # For reflected angle calibration.
    **settings
)
# We need the summed direct beam for the reflectivity
directFgd = ReflectometryILLSumForeground(direct.OutputWorkspace)

# Reflected beam
reflected = ReflectometryILLPreprocess(
    Run='ILL/D17/317370.nxs',
    DirectBeamPositionWorkspace='direct_beam_pos',
    **settings
)
reflectivity = ReflectometryILLSumForeground(
    InputWorkspace=reflected,
    DirectForegroundWorkspace=directFgd,
    WavelengthRange=[2, 15],
)

# Reflectivity is a single histogram
print('Histograms in reflectivity workspace: {}'.format(reflectivity.getNumberHistograms()))
# The data is still in wavelength
print('Reflectivity X unit: ' + reflectivity.getAxis(0).getUnit().unitID())

Output:

Histograms in reflectivity workspace: 1
Reflectivity X unit: Wavelength

Example - Sum in momentum transfer

# Use same foreground and background settings for direct and reflected
# beams.
# Python dictionaries can be passed to algorithms as 'keyword arguments'.
settings = {
    'ForegroundHalfWidth':[5],
    'LowAngleBkgOffset': 10,
    'LowAngleBkgWidth': 20,
    'HighAngleBkgOffset': 10,
    'HighAngleBkgWidth': 50,
}

# Direct beam
direct = ReflectometryILLPreprocess(
    Run='ILL/D17/317369.nxs',
    OutputBeamPositionWorkspace='direct_beam_pos',  # For reflected angle calibration.
    **settings
)
# We need the summed direct beam for the reflectivity
directFgd = ReflectometryILLSumForeground(direct.OutputWorkspace)

# Reflected beam
reflected = ReflectometryILLPreprocess(
    Run='ILL/D17/317370.nxs',
    DirectBeamPositionWorkspace='direct_beam_pos',
    **settings
)
reflectivity = ReflectometryILLSumForeground(
    InputWorkspace=reflected,
    DirectForegroundWorkspace=directFgd,
    SummationType='SumInQ',
    WavelengthRange=[0., 14.]
)

# Reflectivity is a single histogram
print('Histograms in reflectivity workspace: {}'.format(reflectivity.getNumberHistograms()))
# The data is still in wavelength
print('Reflectivity X unit: ' + reflectivity.getAxis(0).getUnit().unitID())

Output:

Histograms in reflectivity workspace: 1
Reflectivity X unit: Wavelength

Categories: Algorithms | ILL\Reflectometry | Workflow\Reflectometry

Source

Python: ReflectometryILLSumForeground.py (last modified: 2018-06-21)