Polarised SANS

[sf1919]

Summary

Implement reduction for polarised SANS data so that we can reproduce and improve on the output of the current scientist-developed scripts but with much improved speed (seconds to minutes, instead of hours), reduced opportunities for mistakes, and greater traceability.

Intended outcome

The adaptation of the workflow and new algorithms will allow for a series of different efficiency corrections that need to be calculated and which cannot be accessed from the data files. This will mean users can be provided with fully corrected PA-SANS data as swiftly and efficiently as possible.

Using the technique at ISIS will enable and support research into many areas, but particularly quantum materials and research relevant to sustainability. There will be synergies with polarised reflectometry and crystalline diffraction.

Acceptance criteria

We expect to develop several new algorithms to implement each calculation. As these are produced, they can be tested against the original scripts to ensure accuracy and check performance.

The MVP is the minimum ‘experiment’ that can be done to demonstrate the required benefits. (This needs to be true before we persevere to implement the full set of features in scope.)

How will it work?

The following features are in scope

New math functions for hyperbolic trigonometry.

The following new calibration steps – potentially each to be a new algorithm:

• The periods in the run need to be examined and labelled with their appropriate spin state.
• Calculating the efficiency of the polariser.
• Calculating efficiency and transmission of the analyser based on one measurement.
• Determine the relative time between measurement
• Fitting the time-dependence of the efficiency
• Extrapolating the wavelength dependence of the efficiency
• Calculate the analyzer efficiency and transmission for arbitrary time based on fit results
• Calculating the efficiency of the two spin flippers.
• Calculating the position-dependent efficiency on the detector

Modifications to existing reduction algorithms:

• Extend the existing PolarizationCorrectionWildes algorithm as required.
• Alter the existing WavRangeReduction (the main SANS reduction) algorithm to take a Mantid workspace instead of just a file.
• Modify the existing output save formats to include required additional information.

A polarised SANS reduction will be run by passing a config file containing the parameter values to a wrapper algorithm. The wrapper algorithm will internally call the individual algorithms as required to perform the reduction.

No GUI is required as the preference is to run the reduction via scripts