MonteCarloAbsorption v1¶

Summary¶

Calculates attenuation due to absorption and scattering in a sample & its environment using a weighted Monte Carlo.

Properties¶

Description¶

This algorithm performs a Monte Carlo simulation to calculate the attenuation factor of a given sample for an arbitrary arrangement of sample + container shapes. The algorithm proceeds as follows for each spectra in turn:

• A random point within the sample+container set up is selected and chosen as a scattering point;
• This point then defines an incoming vector from the source position and an outgoing vector to the final detector;
• The total attenuation factor for this path is then calculated as the product of the factor for each defined material of the sample/container that the track passes through.

Known limitations¶

• Only elastic scattering is implemented at the moment.
• The object’s bounding box is used as a starting point for selecting a random point. If the shape of the object is peculiar enough not to occupy much of the bounding box then the generation of the initial scatter point will fail.

Usage¶

Example: A simple spherical sample

#setup the sample shape
sphere = '''<sphere id="sample-sphere">
      <centre x="0" y="0" z="0"/>
      <radius val="0.1" />
  </sphere>'''

ws = CreateSampleWorkspace("Histogram",NumBanks=1)
ws = ConvertUnits(ws,"Wavelength")
CreateSampleShape(ws,sphere)
SetSampleMaterial(ws,ChemicalFormula="V")

#Note: this is a quick and dirty evaluation, in reality you would need more than 300 events per point
wsOut = MonteCarloAbsorption(ws,EventsPerPoint=300)

print "The created workspace has one entry for each spectra: %i" % ws.getNumberHistograms()
print "Just divide your data by the correction to correct for absorption."

Output:

The created workspace has one entry for each spectra: 100
Just divide your data by the correction to correct for absorption.

Example: A simple spherical sample in a cylindrical container

# The algorithm does allow you to set a complex sample environment
# of different materials and shapes, but some of the required methods
# are not exported to python yet.  This will come.

Categories: Algorithms | CorrectionFunctions | AbsorptionCorrections

Source¶

C++ source: MonteCarloAbsorption.cpp

C++ header: MonteCarloAbsorption.h