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# FlatPlatePaalmanPingsCorrection v1¶

## Summary¶

Calculates absorption corrections for a flat plate sample using Paalman & Pings format.

## Properties¶

Name

Direction

Type

Default

Description

SampleWorkspace

Input

MatrixWorkspace

Mandatory

Name for the input sample workspace

SampleChemicalFormula

Input

string

Sample chemical formula

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

0.1

The value for the sample Mass density (g/cm^3) or Number density (1/Angstrom^3).

SampleThickness

Input

number

0

Sample thickness in cm

SampleAngle

Input

number

0

Angle between incident beam and normal to flat plate surface

CanWorkspace

Input

MatrixWorkspace

Name for the input container workspace

CanChemicalFormula

Input

string

Container chemical formula

CanCoherentXSection

Input

number

0

The coherent cross-section for the can material in barns. To be used instead of Chemical Formula.

CanIncoherentXSection

Input

number

0

The incoherent cross-section for the can material in barns. To be used instead of Chemical Formula.

CanAttenuationXSection

Input

number

0

The absorption cross-section for the can material in barns. To be used instead of Chemical Formula.

CanDensityType

Input

string

Mass Density

Use of Mass density or Number density for the can. Allowed values: [‘Mass Density’, ‘Number Density’]

CanNumberDensityUnit

Input

string

Atoms

Choose which units CanDensity refers to. Allowed values: [Atoms, Formula Units]. Allowed values: [‘Atoms’, ‘Formula Units’]

CanDensity

Input

number

0.1

The value for the can Mass density (g/cm^3) or Number density (1/Angstrom^3).

CanFrontThickness

Input

number

0

Container front thickness in cm

CanBackThickness

Input

number

0

Container back thickness in cm

NumberWavelengths

Input

number

10

Number of wavelengths for calculation

Interpolate

Input

boolean

True

Interpolate the correction workspaces to match the sample workspace

Emode

Input

string

Elastic

Energy transfer mode. Allowed values: [‘Elastic’, ‘Indirect’, ‘Direct’, ‘Efixed’]

Efixed

Input

number

0

Analyser energy (mev). By default will be read from the instrument parameters. Specify manually to override. This is used only in Efixed energy transfer mode.

OutputWorkspace

Output

WorkspaceGroup

Mandatory

The output corrections workspace group

## Description¶

Calculates absorption corrections for an infinite flat plate sample giving output in the Paalman and Pings absorption factors: $$A_{s,s}$$ (scattering and absorption in sample), $$A_{s,sc}$$ (scattering in sample and absorption in sample and container), $$A_{c,sc}$$ (scattering in container and absorption in sample and container) and $$A_{c,c}$$ (scattering and absorption in container).

Details of the analytical method used to calculate the correction factors is available in RAL Technical Report 74-103.

### Restrictions on the input workspace¶

• The input workspaces must have a fully defined instrument.

• In the energy transfer modes other than Efixed they have to have X axis units of wavelength.

### Efixed mode¶

• In Efixed mode, the correction will be computed for a single wavelength number derived from the analyser or monochromator energy, which by default will be attempted to be read from the instrument parameters (named Efixed), but can also be overridden in the Efixed input property. In this case, the NumberWavelengths and Interpolate options will be ignored.

## Usage¶

Example:

# Create a sample workspace
sample = CreateSampleWorkspace(NumBanks=1, BankPixelWidth=1,
XUnit='Wavelength',
XMin=6.8, XMax=7.9,
BinWidth=0.1)

# Copy and scale it to make a can workspace
can = CloneWorkspace(InputWorkspace=sample)
can = Scale(InputWorkspace=can, Factor=1.2)

# Calculate absorption corrections
corr = FlatPlatePaalmanPingsCorrection(SampleWorkspace=sample,
SampleChemicalFormula='H2-O',
SampleThickness=0.1,
SampleAngle=45,
CanWorkspace=can,
CanChemicalFormula='V',
CanFrontThickness=0.01,
CanBackThickness=0.01,
Emode='Indirect',
Efixed=1.845)

print('Correction workspaces: %s' % (', '.join(corr.getNames())))


Output:

Correction workspaces: corr_ass, corr_assc, corr_acsc, corr_acc