| Geant4 Cross Reference |
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25 //
26 // G4InteractionLawPhysical
27 // --------------------------------------------------------------------
28
29 #include "G4InteractionLawPhysical.hh"
30 #include "Randomize.hh"
31
32 G4InteractionLawPhysical::G4InteractionLawPhysical(const G4String& name)
33 : G4VBiasingInteractionLaw(name)
34 {}
35
36 G4InteractionLawPhysical::~G4InteractionLawPhysical()
37 {}
38
39 void G4InteractionLawPhysical::SetPhysicalCrossSection(G4double crossSection)
40 {
41 if (crossSection < 0.0)
42 {
43 G4Exception("G4InteractionLawPhysical::SetPhysicalCrossSection(..)",
44 "BIAS.GEN.14", JustWarning,
45 "Cross-section value passed is negative. It is set to zero !");
46 crossSection = 0.0;
47 }
48 fCrossSectionDefined = true;
49 fCrossSection = crossSection;
50 }
51
52 G4double G4InteractionLawPhysical::
53 ComputeEffectiveCrossSectionAt(G4double) const
54 {
55 if (!fCrossSectionDefined)
56 {
57 G4Exception("G4InteractionLawPhysical::ComputeEffectiveCrossSection(..)",
58 "BIAS.GEN.15", JustWarning,
59 "Cross-section value requested, but has not been defined yet. Assumes 0 !");
60 }
61 return fCrossSection;
62 }
63
64 G4double G4InteractionLawPhysical::
65 ComputeNonInteractionProbabilityAt(G4double stepLength) const
66 {
67 if (!fCrossSectionDefined)
68 {
69 G4Exception("G4InteractionLawPhysical::ComputeNonInteractionProbability(..)",
70 "BIAS.GEN.16", JustWarning,
71 "Non interaction probabitlity value requested, but cross section has not been defined yet. Assumes it to be 0 !");
72 }
73 // -- allows zero cross-section case, by convention:
74 if ( fCrossSection == 0.0 ) return 1.0;
75 else return std::exp(-fCrossSection*stepLength);
76 }
77
78 G4double G4InteractionLawPhysical::SampleInteractionLength()
79 {
80 if ( !fCrossSectionDefined || fCrossSection < 0.0 )
81 {
82 G4Exception("G4InteractionLawPhysical::Sample(..)",
83 "BIAS.GEN.17", FatalException,
84 "Trying to sample while cross-section is not defined or < 0 !");
85 }
86 if ( fCrossSection == 0.0 ) return DBL_MAX;
87
88 fNumberOfInteractionLength = -std::log( G4UniformRand() );
89 return fNumberOfInteractionLength/fCrossSection;
90 }
91
92 G4double G4InteractionLawPhysical::
93 UpdateInteractionLengthForStep(G4double truePathLength)
94 {
95 fNumberOfInteractionLength -= truePathLength*fCrossSection;
96
97 if ( fNumberOfInteractionLength < 0 )
98 {
99 G4ExceptionDescription ed;
100 ed << " Negative number of interaction length for `" << GetName()
101 << "' " << fNumberOfInteractionLength << ", set it to zero !" << G4endl;
102 G4Exception("G4InteractionLawPhysical::UpdateInteractionLengthForStep(...)",
103 "BIAS.GEN.13", JustWarning, ed);
104 fNumberOfInteractionLength = 0.;
105 }
106 return fNumberOfInteractionLength/fCrossSection;
107 }
108