[Requirement] Simple powder diffraction data reduction workflow

[jl-wynen]

Executive summary

Implement a powder diffraction data reduction workflow for DREAM using McStas/GEANT4 simulation of a powder sample in a container.

Context and background knowledge

This development is a first step for powder data reduction workflow specific to DREAM.

References

See SNSPowderReduction

Environment

Assumptions

The input files are from McStas/GEANT4 simulations of different samples:

• Two runs of a powder Diamond sample in a container. Note that 2 runs are used in order to implement the summation of runs during reduction
• A run with the container only
• A vanadium run (for normalisation)

These simulations were run in a High Flux configuration of the instrument.

Use-cases

The diagram below shows the reduction workflow with all samples

Legend:

• Oval with dashed contour: algorithms to be implemented in Scipp & co
• Grey background: reduction steps common to all types of samples
• Non-grey colored background: steps specific to the sample whose cell is of the same color

Preconditions

Algorithms to be implemented in Scipp

• WFM stitching [Requirement] WFM stitching #26
• Lorentz correction Implement Lorentz correction #18
• Remove low-TOF resolution [Requirement] Remove low resolution ToF #23
• Normalize by current [Requirement] Normalisation by current #30
• Strip Vanadium peaks for the Vanadium run only [Requirement] Strip vanadium peaks #24

Inputs

csv files for Sample in container (2 files), container alone and Vanadium.

The csv files are stored at link. There are 2 Vanadium runs that could be used for normalization:

• data_dream_vanadium_inc_coh.csv.zip contains coherent and incoherent scattering. The algorithm StripVanadiumPeaks needs to be applied to extract the background
• data_dream_vanadium.csv.zip contains only the incoherent scattering. No filtering of Bragg peaks is necessary.

Note that the NeXus files are not available yet.

Methodology

Sciline

Outputs

Reduced dataset and xye file to be loaded in analysis software

Which interfaces are required?

Jupyter notebook

Test cases

Meaningful xye file of reduced data (sample in container, vanadium and container)

Comments

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