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MRGetTheta v1

Summary

Get the theta scattering angle for the Magnetism Reflectometer (radians).

Properties

Name	Direction	Type	Default	Description
Workspace	Input	Workspace	Mandatory	Workspace containing MR data
AngleOffset	Input	number	0	Angle offset (rad)
UseSANGLE	Input	boolean	False	If True, use SANGLE as the scattering angle. If False, use DANGLE.
SpecularPixel	Input	number	0	Pixel position of the specular reflectivity [optional]
DirectPixelOverwrite	Input	number	Optional	DIRPIX overwrite value
DAngle0Overwrite	Input	number	Optional	DANGLE0 overwrite value (degrees)
Theta	Output	number		Scattering angle theta (rad)

Description

Calculates the reflection angle theta for a Magnetism Reflectometer workspace. There are two options:

Use SANGLE

This option simply reads in the SANGLE value and returns it in radians. SANGLE is read from an encoder on the sample stage.

Use DANGLE

Used when UseSANGLE is set to false. DANGLE tracks the angle between the incoming beam and the detector relative to an offset (DANGLE0). When everything is aligned, \(\theta=(DANGLE-DANGLE0)/2\).

The reflected beam should be aligned to fall on the detector pixel stored in the DIRPIX log. When it’s not the case, the theta angle will be corrected accordingly. If the SpecularPixel property is set, the reflection angle will be given by:

\(\theta=(DANGLE-DANGLE0)/2 + (DIRPIX - SpecularPixel) * W / 2L\)

where W is the pixel width (0.7 mm) and L is the sample-to-detector distance.

With both options, an offset can be added to the resulting angle by setting the AngleOffset property.

Categories: AlgorithmIndex | Reflectometry\SNS

Source

Python: MRGetTheta.py