G4InteractionLawPhysical.cc

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// G4InteractionLawPhysical
// --------------------------------------------------------------------
 
#include "G4InteractionLawPhysical.hh"
#include "Randomize.hh"
 
G4InteractionLawPhysical::G4InteractionLawPhysical(const G4String& name)
  : G4VBiasingInteractionLaw(name)
{}
 
G4InteractionLawPhysical::~G4InteractionLawPhysical()
{}
 
void G4InteractionLawPhysical::SetPhysicalCrossSection(G4double crossSection)
{
  if (crossSection < 0.0)
  {
    G4Exception("G4InteractionLawPhysical::SetPhysicalCrossSection(..)",
                "BIAS.GEN.14", JustWarning,
                "Cross-section value passed is negative. It is set to zero !");
    crossSection = 0.0;
  }
  fCrossSectionDefined = true;
  fCrossSection = crossSection;
}
 
G4double G4InteractionLawPhysical::
ComputeEffectiveCrossSectionAt(G4double) const
{
  if (!fCrossSectionDefined)
  {
    G4Exception("G4InteractionLawPhysical::ComputeEffectiveCrossSection(..)",
                "BIAS.GEN.15", JustWarning,
                "Cross-section value requested, but has not been defined yet. Assumes 0 !");
  }
  return fCrossSection;
}
 
G4double G4InteractionLawPhysical::
ComputeNonInteractionProbabilityAt(G4double stepLength) const
{
  if (!fCrossSectionDefined)
  {
    G4Exception("G4InteractionLawPhysical::ComputeNonInteractionProbability(..)",
                "BIAS.GEN.16", JustWarning,
                "Non interaction probabitlity value requested, but cross section has not been defined yet. Assumes it to be 0 !");
  }
  // -- allows zero cross-section case, by convention:
  if ( fCrossSection == 0.0 ) return 1.0;
  else return std::exp(-fCrossSection*stepLength);
}
 
G4double G4InteractionLawPhysical::SampleInteractionLength()
{
  if ( !fCrossSectionDefined || fCrossSection < 0.0 )
  {
    G4Exception("G4InteractionLawPhysical::Sample(..)",
                "BIAS.GEN.17", FatalException,
                "Trying to sample while cross-section is not defined or < 0 !");
  }
  if ( fCrossSection == 0.0 ) return DBL_MAX;
 
  fNumberOfInteractionLength = -std::log( G4UniformRand() );
  return fNumberOfInteractionLength/fCrossSection;
}
 
G4double G4InteractionLawPhysical::
UpdateInteractionLengthForStep(G4double truePathLength)
{
  fNumberOfInteractionLength -= truePathLength*fCrossSection;
  
  if ( fNumberOfInteractionLength < 0 ) 
  {
    G4ExceptionDescription ed;
    ed << " Negative number of interaction length for `" << GetName()
       << "' " << fNumberOfInteractionLength << ", set it to zero !" << G4endl; 
    G4Exception("G4InteractionLawPhysical::UpdateInteractionLengthForStep(...)",
                "BIAS.GEN.13", JustWarning, ed);
    fNumberOfInteractionLength = 0.;
  }
  return  fNumberOfInteractionLength/fCrossSection;
}