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26 ////////////////////////////////////////////////////////////////////////////////
27 // //
28 // File: G4AlphaDecay.cc //
29 // Author: D.H. Wright (SLAC) //
30 // Date: 20 October 2014 //
31 // //
32 ////////////////////////////////////////////////////////////////////////////////
33
34 #include "G4AlphaDecay.hh"
35 #include "G4IonTable.hh"
36 #include "Randomize.hh"
37 #include "G4ThreeVector.hh"
38 #include "G4DynamicParticle.hh"
39 #include "G4DecayProducts.hh"
40 #include "G4PhysicalConstants.hh"
41 #include "G4SystemOfUnits.hh"
42 #include <iostream>
43 #include <iomanip>
44
45 G4AlphaDecay::G4AlphaDecay(const G4ParticleDefinition* theParentNucleus,
46 const G4double& branch, const G4double& Qvalue,
47 const G4double& excitationE,
48 const G4Ions::G4FloatLevelBase& flb)
49 : G4NuclearDecay("alpha decay", Alpha, excitationE, flb), transitionQ(Qvalue)
50 {
51 SetParent(theParentNucleus); // Store name of parent nucleus, delete G4MT_parent
52 SetBR(branch);
53
54 SetNumberOfDaughters(2);
55 G4IonTable* theIonTable =
56 (G4IonTable*)(G4ParticleTable::GetParticleTable()->GetIonTable());
57 G4int daughterZ = theParentNucleus->GetAtomicNumber() - 2;
58 G4int daughterA = theParentNucleus->GetAtomicMass() - 4;
59 SetDaughter(0, theIonTable->GetIon(daughterZ, daughterA, excitationE, flb) );
60 SetDaughter(1, "alpha");
61 }
62
63
64 G4AlphaDecay::~G4AlphaDecay()
65 {}
66
67
68 G4DecayProducts* G4AlphaDecay::DecayIt(G4double)
69 {
70 // Fill G4MT_parent with theParentNucleus (stored by SetParent in ctor)
71 CheckAndFillParent();
72
73 // Fill G4MT_daughters with alpha and residual nucleus (stored by SetDaughter)
74 CheckAndFillDaughters();
75
76 G4double alphaMass = G4MT_daughters[1]->GetPDGMass();
77 // Excitation energy included in PDG mass
78 G4double nucleusMass = G4MT_daughters[0]->GetPDGMass();
79
80 // Q value was calculated from atomic masses.
81 // Use it to get correct alpha energy.
82 G4double cmMomentum = std::sqrt(transitionQ*(transitionQ + 2.*alphaMass)*
83 (transitionQ + 2.*nucleusMass)*
84 (transitionQ + 2.*alphaMass + 2.*nucleusMass) )/
85 (transitionQ + alphaMass + nucleusMass)/2.;
86
87 // Set up final state
88 // parentParticle is set at rest here because boost with correct momentum
89 // is done later
90 G4DynamicParticle parentParticle(G4MT_parent, G4ThreeVector(0,0,0), 0.0);
91 G4DecayProducts* products = new G4DecayProducts(parentParticle);
92
93 G4double costheta = 2.*G4UniformRand()-1.0;
94 G4double sintheta = std::sqrt(1.0 - costheta*costheta);
95 G4double phi = twopi*G4UniformRand()*rad;
96 G4ThreeVector direction(sintheta*std::cos(phi),sintheta*std::sin(phi),
97 costheta);
98
99 G4double KE = std::sqrt(cmMomentum*cmMomentum + alphaMass*alphaMass)
100 - alphaMass;
101 G4DynamicParticle* daughterparticle =
102 new G4DynamicParticle(G4MT_daughters[1], direction, KE, alphaMass);
103 products->PushProducts(daughterparticle);
104
105 KE = std::sqrt(cmMomentum*cmMomentum + nucleusMass*nucleusMass) - nucleusMass;
106 daughterparticle =
107 new G4DynamicParticle(G4MT_daughters[0], -1.0*direction, KE, nucleusMass);
108 products->PushProducts(daughterparticle);
109
110 // Energy conservation check
111 // For alpha decays, do final energy check against reaction Q value
112 // which is well-measured using atomic mass differences. Nuclear masses
113 // should not be used since they are not usually directly measured and we
114 // always decay atoms and not fully stripped nuclei.
115 /*
116 G4int nProd = products->entries();
117 G4DynamicParticle* temp = 0;
118 G4double Esum = 0.0;
119 for (G4int i = 0; i < nProd; i++) {
120 temp = products->operator[](i);
121 Esum += temp->GetKineticEnergy();
122 }
123 G4double eCons = (transitionQ - Esum)/keV;
124 if (eCons > 1.e-07) G4cout << " Alpha decay check: Ediff (keV) = " << eCons << G4endl;
125 */
126 return products;
127 }
128
129
130 void G4AlphaDecay::DumpNuclearInfo()
131 {
132 G4cout << " G4AlphaDecay for parent nucleus " << GetParentName() << G4endl;
133 G4cout << " decays to " << GetDaughterName(0) << " + " << GetDaughterName(1)
134 << " with branching ratio " << GetBR() << "% and Q value "
135 << transitionQ << G4endl;
136 }
137
138