CalculateGammaBackground does not copy the errors to the output workspace

[Martyn Gigg]

The CalculateGammaBackground algorithm implemented for Vesuvio in #8378 does not copy the errors from the input workspace to the corrected workspace and leaves them at zero. Trying to use the fitting with this then results in lots of divide by zero errors.

This test script demonstrates the problem:

from mantid.simpleapi import *

#
# Load
# 
runs = "14188-14195"
spectra = "135-142"
diff_type="SingleDifference" # Allowed values=Single,Double,Thick
ip_file = "IP0004_10.par"

raw_ws = LoadVesuvio(Filename=runs, SpectrumList=spectra,
                     Mode=diff_type,InstrumentParFile=ip_file)
raw_ws = CropWorkspace(raw_ws,XMin=50.0,XMax=562.0)


#
# Correct - Usually this string would come out of being constructed from Fit
#
mass1_str = "name=GramCharlierComptonProfile,WorkspaceIndex=0,Mass=1.007900,HermiteCoeffs=1 0 0,Width=4.226288,FSECoeff=0.498073,C_0=57.941101"
mass2_str = "name=GaussianComptonProfile,WorkspaceIndex=0,Mass=27.000000,Width=13.000000,Intensity=1.626268"
mass3_str = "name=GaussianComptonProfile,WorkspaceIndex=0,Mass=91.200000,Width=26.000000,Intensity=2.977515"
func_str = "%s;%s;%s" %(mass1_str,mass2_str,mass3_str)

background,corrected = CalculateGammaBackground(InputWorkspace=raw_ws, ComptonFunction=func_str,WorkspaceIndexList=0)

# Fit corrected
# Convert to seconds
ScaleX(InputWorkspace='corrected ',OutputWorkspace='corrected ',Operation='Multiply',Factor=1e-06)
ties_str = "f1.Width=10.000000,f2.Width=25.000000"
constraints_str = "2.000000 < f0.Width < 7.000000"

Fit(InputWorkspace='corrected ',Function=function_str,Ties=ties_str,Constraints=constraints_str,
        Output='fit', CreateOutput=True,OutputCompositeMembers=True,MaxIterations=5000,
        Minimizer="Levenberg-Marquardt,AbsError=1e-08,RelError=1e-08")
# Convert back to microseconds
ScaleX(InputWorkspace='fit_Workspace',OutputWorkspace='fit_Workspace',Operation='Multiply',Factor=1e06)
ScaleX(InputWorkspace='corrected ',OutputWorkspace='corrected ',Operation='Multiply',Factor=1e06)

[Martyn Gigg]

Formatting changes to put the methods back in the right order

Refs #9166

Changeset: 0b44233e6593a3665bbc567f912b404d571775ae

[Martyn Gigg]

Copy errors across to corrected workspace for all cases.

Refs #9166

Changeset: 72cf3d077c02584227d9a716e83b118801f7eee2

[Martyn Gigg]

Branch: ​feature/9166_errors_on_calculategammabackground

Tester: Use the script in the description to run the gamma correction. The location of the required files is described ​here

[Keith Brown]

Merge remote-tracking branch 'origin/feature/9166_errors_on_calculategammabackground'

Full changeset: ​6ea8f6edc3e054ae8e9b74486b63c3a59b193b9c

[Stuart Campbell]

This ticket has been transferred to github issue ​10009