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26 //
27 // -------------------------------------------------------------------
28 // GEANT 4 class implementation file
29 //
30 // CERN, Geneva, Switzerland
31 //
32 // File name: G4NeutronField.cc
33 //
34 // Author: Alessandro Brunengo (Alessandro.Brunengo@ge.infn.it)
35 //
36 // Creation date: 5 June 2000
37 // -------------------------------------------------------------------
38
39 #include "G4NeutronField.hh"
40 #include "G4PhysicalConstants.hh"
41 #include "G4SystemOfUnits.hh"
42 #include "G4VNuclearDensity.hh"
43 #include "G4FermiMomentum.hh"
44
45 G4NeutronField::G4NeutronField(G4V3DNucleus * aNucleus) :
46 G4VNuclearField(aNucleus), theDensity(theNucleus->GetNuclearDensity())
47 {
48 theA = theNucleus->GetMassNumber();
49 theZ = theNucleus->GetCharge();
50 theFermi.Init(theA, theZ);
51 theR = 2.*theNucleus->GetOuterRadius();
52 for (G4double aR=0.;aR<theR; aR+=0.3*fermi)
53 {
54 G4ThreeVector aPosition(0,0,aR);
55 G4double density = GetDensity(aPosition);
56 G4double fermiMom = GetFermiMomentum(density);
57 theFermiMomBuffer.push_back(fermiMom);
58 }
59 {
60 G4ThreeVector aPosition(0,0,theR);
61 G4double density = GetDensity(aPosition);
62 G4double fermiMom = GetFermiMomentum(density);
63 theFermiMomBuffer.push_back(fermiMom);
64 }
65 {
66 G4ThreeVector aPosition(0,0,theR+0.001*fermi);
67 theFermiMomBuffer.push_back(0);
68 }
69 {
70 G4ThreeVector aPosition(0,0,1.*m);
71 theFermiMomBuffer.push_back(0);
72 }
73 }
74
75 G4NeutronField::~G4NeutronField()
76 { }
77
78 G4double G4NeutronField::GetField(const G4ThreeVector & aPosition)
79 {
80 G4double x = aPosition.mag();
81 unsigned int index = static_cast<unsigned int>(x/(0.3*fermi));
82 if( (index+2) > theFermiMomBuffer.size()) return theFermiMomBuffer.back();
83 G4double y1 = theFermiMomBuffer[index];
84 G4double y2 = theFermiMomBuffer[index+1];
85 G4double x1 = (0.3*fermi)*index;
86 G4double x2 = (0.3*fermi)*(index+1);
87 G4double fermiMom = y1 + (x-x1)*(y2-y1)/(x2-x1);
88 return -1*(fermiMom*fermiMom)/(2*neutron_mass_c2);
89 }
90
91 G4double G4NeutronField::GetBarrier()
92 {
93 /*
94 * G4double A = theNucleus->GetMassNumber();
95 * G4double Z = theNucleus->GetCharge();
96 *
97 * return G4NucleiPropertiesTable::GetBindingEnergy(Z, A)/A;
98 */
99 return 0.;
100 }
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