\(\renewcommand\AA{\unicode{x212B}}\)

PaalmanPingsMonteCarloAbsorption v1¶

Summary ¶

Calculates absorption corrections in Paalman & Pings formalism for a given sample and optionally its environment using a Monte Carlo simulation.

Properties ¶

Name	Direction	Type	Default	Description
InputWorkspace	Input	Workspace	Mandatory	Workspace with the measurement of the sample [in a container].
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
SparseInstrument	Input	boolean	False	Whether to spatially approximate the instrument for faster calculation.
NumberOfDetectorRows	Input	number	3	Number of detector rows in the detector grid of the sparse instrument.
NumberOfDetectorColumns	Input	number	2	Number of detector columns in the detector grid of the sparse instrument.
BeamHeight	Input	number	1	Height of the beam (cm)
BeamWidth	Input	number	1	Width of the beam (cm)
Shape	Input	string	Preset	Geometric shape of the sample environment. Allowed values: [‘Preset’, ‘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)
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).
ContainerFrontThickness	Input	number	0	Front thickness of the container environment (cm)
ContainerBackThickness	Input	number	0	Back thickness of the container environment (cm)
ContainerRadius	Input	number	0	Outer radius of the sample environment (cm)
ContainerInnerRadius	Input	number	0	Inner radius of the container environment (cm)
ContainerOuterRadius	Input	number	0	Outer radius of the container environment (cm)
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).
CorrectionsWorkspace	Output	WorkspaceGroup	corrections	Name of the workspace group to save correction factors

Description ¶

This algorithm calculates the attenuation factors in the Paalman Pings formalism using a Monte Carlo simulation.

Three simple shapes are supported: FlatPlate, Cylinder, and Annulus. Each shape is defined by the corresponding set of geometric parameters.

If the Preset shape option is chosen, the algorithm will use the sample and container shapes defined in the workspace.

Inelastic, quasielastic and elastic measurements are supported, both for direct and indirect geometry instruments.

Height is a common property for the sample and container regardless the shape.

Below are the required properties for each specific shape:

FlatPlate ¶

SampleThickness
SampleWidth
SampleCenter
SampleAngle
ContainerFrontThickness
ContainerBackThickness

Cylinder ¶

SampleRadius
ContainerRadius stands for the outer radius of the annular container, inner radius of which is the same as the radius of the sample.

Annulus ¶

ContainerInnerRadius
SampleInnerRadius
SampleOuterRadius
ContainerOuterRadius

The sample and container shapes and materials are set by SetSample.

The actual calculations are performed using MonteCarloAbsorption for each individual correction term.

The corrections should be applied by the ApplyPaalmanPingsCorrection, where you can find further documentation on the signification of the correction terms and the method.

Note

When container is specified, it is assumed to be tightly wrapping the sample of corresponding shape; that is, there is no gap between the sample and the container.

Note

All the shape arguments are supposed to be in centimeters.

Usage ¶

Example - FlatPlate

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')

corrections = PaalmanPingsMonteCarloAbsorption(
        InputWorkspace=sample_ws,
        Shape='FlatPlate',
        BeamHeight=2.0,
        BeamWidth=2.0,
        Height=2.0,
        SampleWidth=2.0,
        SampleThickness=0.1,
        SampleChemicalFormula='H2-O',
        SampleDensity=1.0,
        ContainerFrontThickness=0.02,
        ContainerBackThickness=0.02,
        ContainerChemicalFormula='V',
        ContainerDensity=6.0,
        CorrectionsWorkspace='flat_plate_corr'
    )

ass_ws = corrections[0]
assc_ws = corrections[1]
acsc_ws = corrections[2]
acc_ws = corrections[3]

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

Y-Unit Label of flat_plate_corr_ass: Attenuation factor
Y-Unit Label of flat_plate_corr_assc: Attenuation factor
Y-Unit Label of flat_plate_corr_acsc: Attenuation factor
Y-Unit Label of flat_plate_corr_acc: Attenuation factor

Example - Cylinder

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')

corrections = PaalmanPingsMonteCarloAbsorption(
        InputWorkspace=sample_ws,
        Shape='Cylinder',
        BeamHeight=2.0,
        BeamWidth=2.0,
        Height=2.0,
        SampleRadius=0.2,
        SampleChemicalFormula='H2-O',
        SampleDensity=1.0,
        ContainerRadius=0.22,
        ContainerChemicalFormula='V',
        ContainerDensity=6.0,
        CorrectionsWorkspace='cylinder_corr'
    )

ass_ws = corrections[0]
assc_ws = corrections[1]
acsc_ws = corrections[2]
acc_ws = corrections[3]

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

Y-Unit Label of cylinder_corr_ass: Attenuation factor
Y-Unit Label of cylinder_corr_assc: Attenuation factor
Y-Unit Label of cylinder_corr_acsc: Attenuation factor
Y-Unit Label of cylinder_corr_acc: Attenuation factor

Example - Annulus

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')

corrections = PaalmanPingsMonteCarloAbsorption(
        InputWorkspace=sample_ws,
        Shape='Annulus',
        BeamHeight=2.0,
        BeamWidth=2.0,
        Height=2.0,
        SampleInnerRadius=0.2,
        SampleOuterRadius=0.4,
        SampleChemicalFormula='H2-O',
        SampleDensity=1.0,
        ContainerInnerRadius=0.19,
        ContainerOuterRadius=0.41,
        ContainerChemicalFormula='V',
        ContainerDensity=6.0,
        CorrectionsWorkspace='annulus_corr'
    )

ass_ws = corrections[0]
assc_ws = corrections[1]
acsc_ws = corrections[2]
acc_ws = corrections[3]

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

Y-Unit Label of annulus_corr_ass: Attenuation factor
Y-Unit Label of annulus_corr_assc: Attenuation factor
Y-Unit Label of annulus_corr_acsc: Attenuation factor
Y-Unit Label of annulus_corr_acc: Attenuation factor

Example - Preset Shape

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')

# define example geometries for the Sample and Container
SetSample(sample_ws, Geometry={'Shape': 'Cylinder', 'Height': 4.0, 'Radius': 2.0, 'Center': [0.,0.,0.]},
            Material={'ChemicalFormula': 'Ni', 'MassDensity': 7.0},
            ContainerGeometry={'Shape': 'HollowCylinder', 'Height': 4.0, 'InnerRadius': 2.0,
            'OuterRadius': 3.5},
            ContainerMaterial={'ChemicalFormula': 'V'})

corrections = PaalmanPingsMonteCarloAbsorption(
        InputWorkspace=sample_ws,
        Shape='Preset',
        BeamHeight=2.0,
        BeamWidth=2.0,
        CorrectionsWorkspace='annulus_corr'
    )

# alternatively, run the corrections with the sample material overridden but preset shape used
corrections = PaalmanPingsMonteCarloAbsorption(
        InputWorkspace=sample_ws,
        Shape='Preset',
        BeamHeight=2.0,
        BeamWidth=2.0,
        SampleChemicalFormula='H2-O',
        SampleDensity=1.0,
        CorrectionsWorkspace='annulus_corr'
    )

ass_ws = corrections[0]
assc_ws = corrections[1]
acsc_ws = corrections[2]
acc_ws = corrections[3]

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

Y-Unit Label of annulus_corr_ass: Attenuation factor
Y-Unit Label of annulus_corr_assc: Attenuation factor
Y-Unit Label of annulus_corr_acsc: Attenuation factor
Y-Unit Label of annulus_corr_acc: Attenuation factor

References ¶

H. H. Paalman, and C. J. Pings. Numerical Evaluation of X‐Ray Absorption Factors for Cylindrical Samples and Annular Sample Cells, Journal of Applied Physics 33.8 (1962) 2635–2639 doi: 10.1063/1.1729034

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

Source ¶

Python: PaalmanPingsMonteCarloAbsorption.py