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CalculateMonteCarloAbsorption v1¶

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)

Input

number

0

Radius of the sample environment (cm)

Input

number

0

Inner radius of the sample environment (cm)

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)

Input

number

0

Inner radius of the container environment (cm)

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