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VesuvioTOFFit v1¶

../_images/ImageNotFound.png — Enable screenshots using DOCS_SCREENSHOTS in CMake¶

Summary ¶

Processes runs for Vesuvio at ISIS

Properties ¶

Name	Direction	Type	Default	Description
InputWorkspace	Input	MatrixWorkspace	Mandatory	Input TOF workspace
Masses	Input	dbl list	Mandatory	Mass values for fitting
MassProfiles	Input	string	Mandatory	Functions used to approximate mass profile. The format is function=Function1Name,param1=val1,param2=val2;function=Function2Name,param3=val3,param4=val4
WorkspaceIndex	Input	long	0	Workspace index for fit. [Default=0]
Background	Input	string		Function used to fit the background. The format is function=FunctionName,param1=val1,param2=val2
IntensityConstraints	Input	string		A semi-colon separated list of intensity constraints defined as lists e.g [0,1,0,-4];[1,0,-2,0]
Ties	Input	string		A string representing the ties to be applied to the fit
FitMode	Input	string	bank	Fit either bank-by-bank or detector-by-detector. Allowed values: [‘bank’, ‘spectrum’]
MaxIterations	Input	long	5000	Maximum number of fitting iterations
Minimizer	Input	string	Levenberg-Marquardt,AbsError=1e-08,RelError=1e-08	String defining the minimizer
OutputWorkspace	Output	MatrixWorkspace	Mandatory	The name of the fitted workspaces.
FitParameters	Output	TableWorkspace	Mandatory	The name of the fitted parameter workspaces.
Chi2	Output	number		The value of the Chi-Squared.

Description ¶

Runs a Time of Flight (TOF) fit for preprocessed Vesuvio data. This algorithm also constructs the constraints, ties, function strings for the fit based on the inputs.

Usage ¶

Example - VesuvioTOFFit

###### Simulates LoadVesuvio with spectrum number 135-136 #################
tof_ws = CreateSimulationWorkspace(Instrument='Vesuvio',BinParams=[50,0.5,562],UnitX='TOF')
tof_ws = CropWorkspace(tof_ws,StartWorkspaceIndex=134,EndWorkspaceIndex=135) # index one less than spectrum number
tof_ws = ConvertToPointData(tof_ws)
SetInstrumentParameter(tof_ws, ParameterName='t0',ParameterType='Number',Value='0.5')
SetInstrumentParameter(tof_ws, ParameterName='sigma_l1', ParameterType='Number', Value='0.021')
SetInstrumentParameter(tof_ws, ParameterName='sigma_l2', ParameterType='Number', Value='0.023')
SetInstrumentParameter(tof_ws, ParameterName='sigma_tof', ParameterType='Number', Value='0.3')
SetInstrumentParameter(tof_ws, ParameterName='sigma_theta', ParameterType='Number', Value='0.028')
SetInstrumentParameter(tof_ws, ParameterName='hwhm_lorentz', ParameterType='Number', Value='24.0')
SetInstrumentParameter(tof_ws, ParameterName='sigma_gauss', ParameterType='Number', Value='73.0')
# Algorithm allows separate parameters for the foils
SetInstrumentParameter(tof_ws, ComponentName='foil-pos0', ParameterName='hwhm_lorentz',
                       ParameterType='Number', Value='144.0')
SetInstrumentParameter(tof_ws, ComponentName='foil-pos0', ParameterName='sigma_gauss',
                       ParameterType='Number', Value='20.0')
SetInstrumentParameter(tof_ws, ComponentName='foil-pos1', ParameterName='hwhm_lorentz',
                       ParameterType='Number', Value='144.0')
SetInstrumentParameter(tof_ws, ComponentName='foil-pos1', ParameterName='sigma_gauss',
                       ParameterType='Number', Value='20.0')

###########################################################################

profiles = "function=GramCharlier,width=[2, 5, 7],hermite_coeffs=[1, 0, 0],k_free=0,sears_flag=1;"\
           "function=Gaussian,width=10;function=Gaussian,width=13;function=Gaussian,width=30;"
background = "function=Polynomial,order=3"

out_ws, fit_params, chi_sq = VesuvioTOFFit(InputWorkspace=tof_ws, Masses=[1.0079, 16.0, 27.0, 133.0],
                                           MassProfiles=profiles, Background=background,
                                           IntensityConstraints='[0,1,0,-4]')