ConvertToDiffractionMDWorkspace: Check on HKL transformation

[Janik Zikovsky]

Peaks from TOPAZ_3131 did not look aligned in the way you would expect when I last tried it. See the Diffraction_Workflow.py script.

To test: run the script to generate a MD workspace in HKL space. In Paraview (or the simple interface), load both the MDWorkspace and the PeaksWorkspace. A PeaksWorkspace of found peaks generated from the Q-space MDWorkspace will work too because it contains the HKL transformation too. Select that the Peaks should be viewed in HKL space. The peaks markers should overlap with the peaks in the data in HKL.

[Janik Zikovsky]

In [14925]:

Fixes #3773: event -> HKL conversion now works well. In TOPAZ_3131 (see sample diffraction workflow script) the peaks look perfectly aligned with the axes.

[Owen Arnold]

See image. Peak positions seem offset.

[Janik Zikovsky]

Hi Owen, I haven't been able to reproduce the issue (see my screenshot). You chose "HKL" in the Peaks paraview plugin?

Here is a simpler script:

# Basic parameters
filename = "TOPAZ_3131_event.nxs"
#Name of the workspaces to create
ws = "TOPAZ_3131"

# Load the original data
LoadEventNexus(Filename=filename,OutputWorkspace=ws)

# Convert to reciprocal space, in the sample frame
ConvertToDiffractionMDWorkspace(InputWorkspace=ws,OutputWorkspace=ws+'_MD',
		OutputDimensions='Q (sample frame)',LorentzCorrection='1')
		
# Find peaks
FindPeaksMD(InputWorkspace=ws+'_MD',MaxPeaks='150',OutputWorkspace=ws+'_peaks')

# Find the UB matrix using the peaks and known lattice parameters
FindUBUsingLatticeParameters(PeaksWorkspace=ws+'_peaks',a='10.3522',b='6.0768',c='4.7276',
		alpha='90',beta='90',gamma='90', NumInitial='20', Tolerance='0.12')
# And index to HKL		
IndexPeaks(PeaksWorkspace=ws+'_peaks', Tolerance='0.12')
		
# Copy the UB matrix back to the original workspace
CopySample(InputWorkspace=ws+'_peaks',OutputWorkspace=ws,
		CopyName='0',CopyMaterial='0',CopyEnvironment='0',CopyShape='0',  CopyLattice=1)
		
SaveIsawPeaks(InputWorkspace=ws+'_peaks', Filename="TOPAZ_3131_found.peaks") 

# Save the MD workspace in Q sample frame to a NXS file. 
#SaveMD(InputWorkspace=ws+'_MD', Filename='TOPAZ_3131_MD_q_sample.nxs')

# ----- Now Convert to HKL space to view in that space ----------- 

# Convert to reciprocal space, in the sample frame
ConvertToDiffractionMDWorkspace(InputWorkspace=ws,OutputWorkspace=ws+'_HKL',
		OutputDimensions='HKL',LorentzCorrection='1')

# Save that for later viewing in paraview
SaveMD(InputWorkspace=ws+'_HKL', Filename='TOPAZ_3131_MD_HKL.nxs')

[Owen Arnold]

Followed the script above. Produces properly aligned peaks. They looked off in my earlier tests probably because I had too many events in my splatter plot and a truncated coloring range.

Please mark this ticket as accepted -> verified and I will mark it as completed.

[Stuart Campbell]

This ticket has been transferred to github issue ​4613