DirectILLApplySelfShielding v1¶

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)

# Create a fake 'empty container' workspace for background subtraction.
ecws = Scale(
    InputWorkspace=ws,
    Factor=0.1
)

DirectILLCollectData(
    InputWorkspace=ws,
    OutputWorkspace='preprocessed',
    ElasticChannelWorkspace=elasticChannelWS,
    IncidentEnergyCalibration='Energy Calibration OFF', # Normally we would do this for IN4.
)

DirectILLCollectData(
    InputWorkspace=ecws,
    OutputWorkspace='preprocessed_ecws',
    ElasticChannelWorkspace=elasticChannelWS,
    IncidentEnergyCalibration='Energy Calibration OFF'
)

sampleGeometry = {
    'Shape': 'Cylinder',
    'Height': 8.0,
    'Radius': 1.5,
    'Center': [0.0, 0.0, 0.0]
}
sampleMaterial = {
    'ChemicalFormula': 'V',
    'SampleNumberDensity': 0.05
}
SetSample(
    InputWorkspace='preprocessed',
    Geometry=sampleGeometry,
    Material=sampleMaterial
)

DirectILLSelfShielding(
    InputWorkspace='preprocessed',
    OutputWorkspace='absorption_corrections',
    SimulationInstrument='Full Instrument', # IN4 is small enough.
    NumberOfSimulatedWavelengths=10
)

DirectILLApplySelfShielding(
    InputWorkspace='preprocessed',
    OutputWorkspace='absorptionCorrected',
    EmptyContainerWorkspace='preprocessed_ecws',
    SelfShieldingCorrectionWorkspace='absorption_corrections'
)

preprocessed = mtd['preprocessed']
maxY = numpy.amax(preprocessed.readY(0))
print('Elastic peak maximum before corrections: {:.3}'.format(maxY))
corrected = mtd['absorptionCorrected']
maxY = numpy.amax(corrected.readY(0))
print('After empty container subtraction and absorption corrections: {:.3}'.format(maxY))