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PolarizationCorrectionFredrikze v1¶

Summary ¶

Makes corrections for polarization efficiencies of the polarizer and analyzer in a reflectometry neutron spectrometer.

Properties ¶

Name	Direction	Type	Default	Description
InputWorkspace	Input	WorkspaceGroup	Mandatory	An input workspace to process.
PolarizationAnalysis	Input	string	PA	What Polarization mode will be used? PNR: Polarized Neutron Reflectivity mode PA: Full Polarization Analysis PNR-PA. Allowed values: [‘PA’, ‘PNR’]
Efficiencies	Input	MatrixWorkspace	Mandatory	A workspace containing the efficiency factors Pp, Ap, Rho and Alpha as histograms
OutputWorkspace	Output	WorkspaceGroup	Mandatory	An output workspace.

Description ¶

Performs wavelength polarization correction on a TOF reflectometer spectrometer.

Algorithm is based on the the paper Fredrikze, H, et al. “Calibration of a polarized neutron reflectometer” Physica B 297 (2001).

Polarizer and Analyzer efficiencies are calculated and used to perform an intensity correction on the input workspace. The input workspace(s) are in units of wavelength inverse angstroms.

In the ideal case \(P_{p} = P_{a} = A_{p} = A_{a} = 1\)

\(\rho = \frac{P_{a}}{P_{p}}\) where rho is bounded by, but inclusive of 0 and 1. Since this ratio is wavelength dependent, rho is a polynomial, which is expressed as a function of wavelength. For example: \(\rho(\lambda) =\sum\limits_{i=0}^{i=2} K_{i}\centerdot\lambda^i\), can be provided as \(K_{0}, K_{1}, K_{2}\)

\(\alpha = \frac{A_{a}}{A_{p}}\) where alpha is bounded by, but inclusive of 0 and 1. Since this ratio is wavelength dependent, alpha is a polynomial, which is expressed as a function of wavelength. For example: \(\alpha(\lambda) =\sum\limits_{i=0}^{i=2} K_{i}\centerdot\lambda^i\), can be provided as \(K_{0}, K_{1}, K_{2}\)

Output from Full Polarization Analysis ¶

The output of this algorithm, as we can see in the table of properties, is a WorkspaceGroup. If the algorithm has been executed with “PA” as the Polarization mode then the resulting WorkspaceGroup will have 4 entries and should be in the format: