\(\renewcommand\AA{\unicode{x212B}}\)

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]')

Categories: AlgorithmIndex | Inelastic\Indirect\Vesuvio

Source

Python: VesuvioTOFFit.py