EPIC: Polarised reflectivity reduction in NR GUI

[gemmaguest]

Some changes are required to be able to run Polref experiments in the ISIS Reflectometry GUI. This would be particularly useful for soft matter users, who are more familiar with the GUI than with the scripts that Polref currently uses. Some of the additional steps used/required for Polref would also be useful for the other instruments, so there is benefit in consolidating the workflows.

A brief summary of the main steps required, in order of priority, is:

Perform polarisation correction:

• Allow to specify polarisation correction workspace file in the GUI similar to a flood workspace instead of using the parameters file - the remaining work needed for this is detailed in Improve the GUI Functionality of the Polarization Efficiencies Combobox In the Refl GUI #34812 .
• Support time slicing of workspace groups in ISIS Reflectometry GUI #35525
• Add algorithm for creating POLREF polarisation correction workspaces #35682 - We would need to be well-documented to make it transparent to users exactly what the algorithm is doing, as users have commented that they currently find this difficult to establish, particularly if trying to read the code.
• Need to be able to customise the order of the flippers to match the workspace (Polref does not use the order currently assumed) - Allow bespoke flipper configurations and output spin state in PolarizationCorrectionWildes #35067
• Labelling of Wildes output workspaces is inverted #34940

Additional steps required for Polref reduction:

• Calibration step for POLREF reductions #34934 - change theta-in based on the calibration file. For summing in Q, need to do full pixel adjustment from the calibration. Review requirements against the algorithm we have already added for INTER, as POLREF should be similar but they measure positions in angles rather than mm.
• Fit the specular peak using Bumps or similar.

General improvements:

• There are currently some bugs in producing the workspace history from the workflow algorithms used by the GUI, in particular when the input is a workspace group. We should fix this so we can fully reproduce the reduction, and it would also aid with transparency.
• Add output stitch options to parameters file #34843 - Adding output stitch options to the parameters file.
• Improving stitched group child workspace names. Also polarization workspace names have been mentioned.

New features:

• Get the error on the fitted peak from the fitter. Bayesian analysis preferred, but would want to be able to turn this off because it's very slow.
• Add diagnostic tools to the GUI to be able to view the flood workspace, background subtraction workspace etc. Using these tools, it should be possible to auto-populate ROIs from fitting performed using the diagnostic tools to speed up the process of entering all the required settings by hand. It should then be possible to manually change these settings, while preventing any further diagnostic fitting from overwriting them.
• Polref run experiments where each sample is very different and requires all the cropping lambda/Q ranges etc. to be adjusted for every run. This is currently quite cumbersome in the GUI because it requires clicking on boxes in different tabs to edit each start and end value. It would be good to think about how we might streamline this.

[rbauststfc]

We have now written an epic to cover this work. The following issues are included in the epic:

• Add polarisation spin state to ISIS ORSO file metadata #36685
• Include multiple datasets in ISIS Reflectometry ORSO ASCII file #36396
• Extend SaveISISReflectometryORSO to output as ORSO Nexus file #37162
• Allow bespoke flipper configurations and output spin state in PolarizationCorrectionWildes #35067
• Allow bespoke input and output spin state in PolarizationCorrectionFredrikze #36981
• Support changes to polarization correction inputs in the ISIS Reflectometry GUI and ReflectometryISISLoadAndProcess #37617
• Add algorithm for creating POLREF polarisation correction workspaces #35682
• Support time slicing of workspace groups in ISIS Reflectometry GUI #35525
• Add algorithm to create a pixel map for POLREF calibration #36978
• Add angle calibration algorithm for POLREF data reduction #36979
• Provide data visualisation tools for POLREF data reduction #36980
• Investigate missing parent algorithm history for workspace groups #36983
• Add pixel masking as step in ISIS Reflectometry reduction #36984
• Review history produced by POLREF GUI reduction #36985
• Angle correction algorithm for ISIS Reflectometry reduction #37065