3.11

DirectILLIntegrateVanadium v1

../_images/DirectILLIntegrateVanadium-v1_dlg.png

DirectILLIntegrateVanadium dialog.

Summary

Integrate vanadium workspace. Part of the TOF workflow at ILL.

Properties

Name Direction Type Default Description
InputWorkspace Input MatrixWorkspace Mandatory Input workspace.
OutputWorkspace Output Workspace Mandatory The output of the algorithm.
Cleanup Input string Cleanup ON What to do with intermediate workspaces. Allowed values: [‘Cleanup ON’, ‘Cleanup OFF’]
SubalgorithmLogging Input string Logging OFF Enable or disable subalgorithms to print in the logs. Allowed values: [‘Logging OFF’, ‘Logging ON’]
EPPWorkspace Input TableWorkspace Mandatory Table workspace containing results from the FindEPP algorithm.
DebyeWallerCorrection Input string Correction ON Enable or disable the correction for the Debye-Waller factor for OutputWorkspace. Allowed values: [‘Correction ON’, ‘Correction OFF’]
Temperature Input number Optional Experimental temperature (Vanadium reduction type only) for the Debye-Waller correction, in Kelvins.

Description

This algorithm integrates the workspace given in InputWorkspace using the ComputeCalibrationCoefVan algorithm. It is part of ILL’s direct geometry reduction algorithms.

Note

At the moment, the integration range is fixed to \pm 3 * FWHM (2\sqrt{2 \ln 2}) times the ‘Sigma’ column in EPPWorkspace).

Input workspaces

The InputWorkspace should be loaded using the DirectILLCollectData algorithm. It will also give the EPP workspace needed for EPPWorkspace.

Vanadium temperature

A correction for the Debye-Waller factor is applied to the integrated vanadium, as explained in the documentation of ComputeCalibrationCoefVan. The temperature for the DWF calculation is taken from the ‘Sample.temperature’ sample log of the InputWorkspace. This value can be overriden by the Temperature property, if needed.

Usage

Example - Integrating fake IN4 workspace

import numpy
import scipy.stats

# Create a fake IN4 workspace.
# We need an instrument and a template first.
empty_IN4 = LoadEmptyInstrument(InstrumentName='IN4')
nHist = empty_IN4.getNumberHistograms()
# Make TOF bin edges.
xs = numpy.arange(530.0, 2420.0, 4.0)
# Make some Gaussian spectra.
ys = 1000.0 * scipy.stats.norm.pdf(xs[:-1], loc=970, scale=60)
# Repeat data for each histogram.
xs = numpy.tile(xs, nHist)
ys = numpy.tile(ys, nHist)
ws = CreateWorkspace(
    DataX=xs,
    DataY=ys,
    NSpec=nHist,
    UnitX='TOF',
    ParentWorkspace=empty_IN4
)
# Manually correct monitor spectrum number as LoadEmptyInstrument does
# not know about such details.
SetInstrumentParameter(
    Workspace=ws,
    ParameterName='default-incident-monitor-spectrum',
    ParameterType='Number',
    Value=str(1)
)
# Add incident energy information to sample logs.
AddSampleLog(
    Workspace=ws,
    LogName='Ei',
    LogText=str(57),
    LogType='Number',
    LogUnit='meV',
    NumberType='Double'
)
# Elastic channel information is missing in the sample logs.
# It can be given as single valued workspace, as well.
elasticChannelWS = CreateSingleValuedWorkspace(107)

# Prepare the workspace for integration.
# We also need the elastic peak position table (EPP).
DirectILLCollectData(
    InputWorkspace=ws,
    OutputWorkspace='preprocessed',
    ElasticChannelWorkspace=elasticChannelWS,
    IncidentEnergyCalibration='Energy Calibration OFF', # Normally enabled for IN4.
    OutputEPPWorkspace='epps'
)

DirectILLIntegrateVanadium(
    InputWorkspace='preprocessed',
    OutputWorkspace='norm-factors',
    EPPWorkspace='epps',
    DebyeWallerCorrection='Correction OFF',
    Temperature=293
)

norms = mtd['norm-factors']
print('Integrated vanadium contains {} bin in each of {} histograms.'
    .format(norms.blocksize(), norms.getNumberHistograms()))

Output:

Integrated vanadium contains 1 bin in each of 396 histograms.

Categories: Algorithms | Workflow\Inelastic