CalculateGammaBackground does not copy the errors to the output workspace

[martyngigg]

The CalculateGammaBackground algorithm implemented for Vesuvio in http://trac.mantidproject.org/mantid/ticket/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:

#!python
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)

[martyngigg]

This issue was originally trac ticket 9166