Create wrapper algorithm for Polarised SANS reduction at ISIS

[rbauststfc]

A wrapper/workflow algorithm is required for the Polarised SANS reduction at ISIS. This algorithm will call relevant calibration and correction algorithms before passing the workspace into the normal SANS WavRangeReduction algorithm. The workflow algorithm should take a config file (expected to be TOML format) containing the relevant parameters for the reduction.

The config file is required to help manage the large number of parameters that the reduction will require. The Polarised SANS reduction will be run via a script and providing a wrapper algorithm will simplify these scripts, as the individual steps should always remain the same.

Further requirements still need to be gathered for this.

Considerations

The current implementation of the workflow (in the scientist scripts) involves some movement of instrument components on the workspaces. The ReductionCore algorithm will reset these so it's important to be clear that any adjustments made in this algorithm will also need to be present in the UserFile to ensure compatibility and correct calculations.

[rbauststfc]

The expected workflow is as follows (still under discussion):

• Convert TOF workspace to wavelength. This should replicate the wavelength conversion steps from the WavRangeReduction algorithm, which should be the following:
  - Read IDF
  - Read userfile
  - Move instrument components as necessary
  - Convert units to wavelength
• Calculate the depolarised transmission of the 3He gas in the analyser cell (Algorithm required for calculating transmission of the analyser #36383)
• Calculate the polarised efficiency of the 3He analyser cell
  - Call algorithm to calculate efficiency (Algorithm required for calculating ISIS SANS analyser efficiencies #36140)
  - Interpolate points (Algorithm required for interpolating the efficiency wavelength dependence #36143)
  - Apply position dependent efficiency correction (Algorithm required to calculate the position-dependent efficiency on the detector #36145)
• Calculate the efficiency of the flipper
  - Read in flipper efficiency file (specified in userfile)
  - Interpolate points (Algorithm required for interpolating the efficiency wavelength dependence #36143)
• Calculate the polarised efficiency of the supermirror polariser
  - Read in supermirror efficiency reference file (specified in userfile)
  - Call algorithm to calculate efficiency from experiment measurements (Algorithm required for calculating efficiency of ISIS SANS polariser #36139)
  - Pause the reduction and display a plot of the calculated efficiency against the reference file values. The user will assess this and indicate whether the reduction should continue (if all is OK) or if it should stop (if there is an issue). The user will correct the userfile to use a different polariser efficiency file, if needed. This part of the workflow should have further discussion to confirm how best to support this requirement, which is essentially to be able to compare the experiment stats against the known good reference file and decide on the fly which to use in the reduction.
  - Interpolate points (Algorithm required for interpolating the efficiency wavelength dependence #36143)
• Pass the analyser, flipper and polariser efficiencies into PolarizationCorrectionWildes to apply the correction.
• Convert the corrected workspace back into TOF and pass it into the standard SANS reduction algorithm (note as part of Alter WavRangeReduction algorithm to take a Mantid workspace #35875 we will consider if it's necessary to perform the conversion back into TOF).