6.4

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CalculateMonteCarloAbsorption v1

../_images/CalculateMonteCarloAbsorption-v1_dlg.png

CalculateMonteCarloAbsorption dialog.

Summary

Calculates indirect absorption corrections for a given sample shape, using a MonteCarlo simulation.

Properties

Name Direction Type Default Description
SampleWorkspace Input Workspace Mandatory Sample Workspace
SampleChemicalFormula Input string   Chemical formula for the sample material
SampleCoherentXSection Input number 0 The coherent cross-section for the sample material in barns. To be used instead of Chemical Formula.
SampleIncoherentXSection Input number 0 The incoherent cross-section for the sample material in barns. To be used instead of Chemical Formula.
SampleAttenuationXSection Input number 0 The absorption cross-section for the sample material in barns. To be used instead of Chemical Formula.
SampleDensityType Input string Mass Density Use of Mass density or Number density for the sample. Allowed values: [‘Mass Density’, ‘Number Density’]
SampleNumberDensityUnit Input string Atoms Choose which units SampleDensity refers to. Allowed values: [Atoms, Formula Units]. Allowed values: [‘Atoms’, ‘Formula Units’]
SampleDensity Input number 0 The value for the sample Mass density (g/cm^3) or Number density (1/Angstrom^3).
BeamHeight Input number 1 Height of the beam (cm)
BeamWidth Input number 1 Width of the beam (cm)
NumberOfWavelengthPoints Input number 10 Number of wavelengths for calculation
EventsPerPoint Input number 1000 Number of neutron events
Interpolation Input string Linear Type of interpolation. Allowed values: [‘Linear’, ‘CSpline’]
MaxScatterPtAttempts Input number 5000 Maximum number of tries made to generate a scattering point
ContainerWorkspace Input Workspace   Container Workspace
ContainerChemicalFormula Input string   Chemical formula for the container material
ContainerCoherentXSection Input number 0 The coherent cross-section for the can material in barns. To be used instead of Chemical Formula.
ContainerIncoherentXSection Input number 0 The incoherent cross-section for the can material in barns. To be used instead of Chemical Formula.
ContainerAttenuationXSection Input number 0 The absorption cross-section for the can material in barns. To be used instead of Chemical Formula.
ContainerDensityType Input string Mass Density Use of Mass density or Number density for the container. Allowed values: [‘Mass Density’, ‘Number Density’]
ContainerNumberDensityUnit Input string Atoms Choose which units ContainerDensity refers to. Allowed values: [Atoms, Formula Units]. Allowed values: [‘Atoms’, ‘Formula Units’]
ContainerDensity Input number 0 The value for the container Mass density (g/cm^3) or Number density (1/Angstrom^3).
Shape Input string FlatPlate Geometric shape of the sample environment. Allowed values: [‘FlatPlate’, ‘Cylinder’, ‘Annulus’]
Height Input number 0 Height of the sample environment (cm)
SampleWidth Input number 0 Width of the sample environment (cm)
SampleThickness Input number 0 Thickness of the sample environment (cm)
SampleCenter Input number 0 Center of the sample environment
SampleAngle Input number 0 Angle of the sample environment with respect to the beam (degrees)
SampleRadius Input number 0 Radius of the sample environment (cm)
SampleInnerRadius Input number 0 Inner radius of the sample environment (cm)
SampleOuterRadius Input number 0 Outer radius of the sample environment (cm)
ContainerFrontThickness Input number 0 Front thickness of the container environment (cm)
ContainerBackThickness Input number 0 Back thickness of the container environment (cm)
ContainerInnerRadius Input number 0 Inner radius of the container environment (cm)
ContainerOuterRadius Input number 0 Outer radius of the container environment (cm)
CorrectionsWorkspace Output WorkspaceGroup corrections Name of the workspace group to save correction factors

Warning

This algorithm is deprecated in favour of PaalmanPingsMonteCarloAbsorption.

Description

This algorithm calculates the absorption factors, required for the Paalman Pings method of absorption corrections, using a Monte Carlo procedure. Currently only the acc and ass factors are calculated.

CalculateMonteCarloAbsorption subsequently calls the SimpleShapeMonteCarloAbsorption v1 algorithm for the calculation of each absorption factor.

There are three existing Shape Options: Flat Plate, Annulus and Cylinder. Each shape is defined by a different set of geometric parameters.

Flat Plate parameters: SampleThickness and SampleWidth for the Sample, ContainerFrontThickness and ContainerBackThickness for the container. Annulus parameters: SampleInnerRadius and SampleOuterRadius for the Sample, ContainerInnerRadius and ContainerOuterRadius for the container. Cylinder parameters: SampleRadius for the sample, ContainerInnerRadius and ContainerOuterRadius for the container.

The location and orientation of the sample can be defined with SampleCenter and SampleAngle.

When container is defined, the corrections are calculated for the inner and outer walls of the container and then they are multiplied together, which is an approximation.

Usage

Example - CalculateMonteCarloAbsorption

sample_ws = CreateSampleWorkspace(Function="Quasielastic",
                                  XUnit="Wavelength",
                                  XMin=-0.5,
                                  XMax=0.5,
                                  BinWidth=0.01)
# Efixed is generally defined as part of the IDF for real data.
# Fake it here
inst_name = sample_ws.getInstrument().getName()
SetInstrumentParameter(sample_ws, ComponentName=inst_name,
    ParameterName='Efixed', ParameterType='Number', Value='4.1')

container_ws = CreateSampleWorkspace(Function="Quasielastic",
                                     XUnit="Wavelength",
                                     XMin=-0.5,
                                     XMax=0.5,
                                     BinWidth=0.01)
SetInstrumentParameter(container_ws, ComponentName=inst_name,
    ParameterName='Efixed', ParameterType='Number', Value='4.1')

corrections = CalculateMonteCarloAbsorption(SampleWorkspace = sample_ws,
                                            SampleChemicalFormula = 'H2-O',
                                            SampleDensityType = 'Mass Density',
                                            SampleDensity = 1.0,
                                            ContainerWorkspace = container_ws,
                                            ContainerChemicalFormula = 'Al',
                                            ContainerDensityType = 'Mass Density',
                                            ContainerDensity = 1.0,
                                            EventsPerPoint = 200,
                                            BeamHeight = 3.5,
                                            BeamWidth = 4.0,
                                            Height = 2.0,
                                            Shape = 'FlatPlate',
                                            SampleWidth = 1.4,
                                            SampleThickness = 2.1,
                                            ContainerFrontThickness = 1.2,
                                            ContainerBackThickness = 1.1)

ass_ws = corrections[0]
acc_ws = corrections[1]

print("Workspaces: " + str(ass_ws.getName()) + ", " + str(acc_ws.getName()))
print("Y-Unit Label of " + str(ass_ws.getName()) + ": " + str(ass_ws.YUnitLabel()))
print("Y-Unit Label of " + str(acc_ws.getName()) + ": " + str(acc_ws.YUnitLabel()))

Output:

Workspaces: corrections_ass, corrections_acc
Y-Unit Label of corrections_ass: Attenuation factor
Y-Unit Label of corrections_acc: Attenuation factor

Categories: AlgorithmIndex | Workflow\Inelastic | CorrectionFunctions\AbsorptionCorrections | Workflow\MIDAS