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25 //
26 //J.M. Quesada (August2008). Based on:
27 //
28 // Hadronic Process: Nuclear De-excitations
29 // by V. Lara (Oct 1998)
30 //
31 // Modified:
32 // 03-09-2008 J.M. Quesada for external choice of inverse cross section option
33 // 06-09-2008 J.M. Quesada Also external choices have been added for superimposed
34 // Coulomb barrier (if useSICB is set true, by default is false)
35 // 17-11-2010 V.Ivanchenko in constructor replace G4VEmissionProbability by
36 // G4EvaporationProbability and do not new and delete probability
37 // object at each call; use G4Pow
38
39 #include "G4EvaporationChannel.hh"
40 #include "G4EvaporationProbability.hh"
41 #include "G4CoulombBarrier.hh"
42 #include "G4NuclearLevelData.hh"
43 #include "G4NucleiProperties.hh"
44 #include "G4Pow.hh"
45 #include "G4Log.hh"
46 #include "G4Exp.hh"
47 #include "G4PhysicalConstants.hh"
48 #include "G4SystemOfUnits.hh"
49 #include "Randomize.hh"
50 #include "G4RandomDirection.hh"
51 #include "G4PhysicsModelCatalog.hh"
52
53 G4EvaporationChannel::G4EvaporationChannel(G4int anA, G4int aZ,
54 G4EvaporationProbability* aprob):
55 G4VEvaporationChannel(),
56 theProbability(aprob),
57 theCoulombBarrier(new G4CoulombBarrier(anA, aZ)),
58 theA(anA), theZ(aZ)
59 {
60 secID = G4PhysicsModelCatalog::GetModelID("model_G4EvaporationChannel");
61 evapMass = G4NucleiProperties::GetNuclearMass(theA, theZ);
62 evapMass2 = evapMass*evapMass;
63 theLevelData = G4NuclearLevelData::GetInstance();
64 }
65
66 G4EvaporationChannel::~G4EvaporationChannel()
67 {
68 delete theCoulombBarrier;
69 }
70
71 void G4EvaporationChannel::Initialise()
72 {
73 theProbability->Initialise();
74 G4VEvaporationChannel::Initialise();
75 }
76
77 G4double G4EvaporationChannel::GetEmissionProbability(G4Fragment* fragment)
78 {
79 theProbability->ResetProbability();
80 G4int fragA = fragment->GetA_asInt();
81 G4int fragZ = fragment->GetZ_asInt();
82 resA = fragA - theA;
83 resZ = fragZ - theZ;
84
85 // Only channels which are physically allowed are taken into account
86 if(resA < theA || resA < resZ || resZ < 0 || (resA == theA && resZ < theZ)
87 || ((resA > 1) && (resA == resZ || resZ == 0)))
88 { return 0.0; }
89
90 G4double exEnergy = fragment->GetExcitationEnergy();
91 G4double fragMass = fragment->GetGroundStateMass();
92 mass = fragMass + exEnergy;
93 resMass = G4NucleiProperties::GetNuclearMass(resA, resZ);
94 if (mass <= evapMass + resMass) { return 0.0; }
95
96 ekinmax = 0.5*((mass-resMass)*(mass+resMass) + evapMass2)/mass - evapMass;
97
98 // for OPTxs=1 elim=0 for all fragments - x-section include the CoulombBarrier
99 G4double elim = 0.0;
100 if(theZ > 0) {
101 bCoulomb = theCoulombBarrier->GetCoulombBarrier(resA, resZ, 0.0);
102
103 // for OPTxs >0 penetration under the barrier is taken into account
104 elim = (0 < OPTxs) ? bCoulomb*0.5 : bCoulomb;
105 }
106 /*
107 G4cout << "G4EvaporationChannel::Initialize Z=" << theZ <<" A=" << theA
108 << " FragZ=" << fragZ << " FragA=" << fragA << G4endl;
109 G4cout << " Eex=" << exEnergy << " CB=" << bCoulomb
110 << " Elim=" << elim << " Efree=" << mass - resMass - evapMass
111 << G4endl;
112 */
113 // Coulomb barrier compound at rest
114 G4double resM = mass - evapMass - elim;
115 if (resM < resMass) { return 0.0; }
116 G4double ekinmin = 0.5*((mass-resM)*(mass+resM) + evapMass2)/mass - evapMass;
117
118 /*
119 G4cout << "Emin= " <<ekinmin<<" Emax= "<<ekinmax
120 << " mass= " << mass << " resM= " << resMass
121 << " evapM= " << evapMass << G4endl;
122 */
123 if(ekinmax <= ekinmin) { return 0.0; }
124
125 theProbability->SetDecayKinematics(resZ, resA, resMass, mass);
126 G4double prob = theProbability->TotalProbability(*fragment, ekinmin,
127 ekinmax, bCoulomb,
128 exEnergy);
129 return prob;
130 }
131
132 G4Fragment* G4EvaporationChannel::EmittedFragment(G4Fragment* theNucleus)
133 {
134 G4double ekin = ekinmax;
135 // assumed, that TotalProbability(...) was already called
136 // if value iz zero no possiblity to sample final state
137 if(resA > 4 && theProbability->GetProbability() > 0.0) {
138 ekin = theProbability->SampleEnergy();
139 }
140 ekin = std::max(ekin, 0.0);
141 G4LorentzVector lv0 = theNucleus->GetMomentum();
142 G4LorentzVector lv(std::sqrt(ekin*(ekin + 2.0*evapMass))*G4RandomDirection(),
143 ekin + evapMass);
144 lv.boost(lv0.boostVector());
145
146 G4Fragment* evFragment = new G4Fragment(theA, theZ, lv);
147 evFragment->SetCreatorModelID(secID);
148 lv0 -= lv;
149 theNucleus->SetZAandMomentum(lv0, resZ, resA);
150 theNucleus->SetCreatorModelID(secID);
151 return evFragment;
152 }
153
154 G4double G4EvaporationChannel::ComputeInverseXSection(G4Fragment* frag,
155 G4double kinEnergy)
156 {
157 G4double p = ComputeProbability(frag, kinEnergy);
158 return (p > 0.0) ? theProbability->RecentXS() : 0.0;
159 }
160
161 G4double G4EvaporationChannel::ComputeProbability(G4Fragment* frag,
162 G4double kinEnergy)
163 {
164 G4double prob = GetEmissionProbability(frag);
165 if (prob <= 0.0) { return 0.0; }
166
167 bCoulomb = (theZ > 0) ? theCoulombBarrier->GetCoulombBarrier(resA, resZ, 0.0) : 0.0;
168 G4double p = theProbability->ComputeProbability(kinEnergy, bCoulomb);
169 return p;
170 }
171