3.9

FlatPlatePaalmanPingsCorrection v1

../_images/FlatPlatePaalmanPingsCorrection-v1_dlg.png

FlatPlatePaalmanPingsCorrection dialog.

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 Mandatory Sample chemical formula
SampleDensityType Input string Mass Density Use of Mass density or Number density. Allowed values: [‘Mass Density’, ‘Number Density’]
SampleDensity Input number 0.1 Mass density (g/cm^3) or Number density (atoms/Angstrom^3)
SampleThickness Input number 0 Sample thickness in cm
SampleAngle Input number 0 Sample angle in degrees
CanWorkspace Input MatrixWorkspace   Name for the input container workspace
CanChemicalFormula Input string   Container chemical formula
CanDensityType Input string Mass Density Use of Mass density or Number density. Allowed values: [‘Mass Density’, ‘Number Density’]
CanDensity Input number 0.1 Mass density (g/cm^3) or Number density (atoms/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 Input number 1 Analyser energy
OutputWorkspace Output WorkspaceGroup Mandatory The output corrections workspace group

Description

Calculates absorption corrections for a flat plate sample giving output in the Paalman & Pings absorption factors: A_{s,s} (correction factor for 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 workspace must have a fully defined instrument that has X axis units of wavelength.

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

Categories: Algorithms | Workflow\MIDAS | CorrectionFunctions\AbsorptionCorrections