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MRGetTheta v1

../_images/MRGetTheta-v1_dlg.png

MRGetTheta dialog.

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