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25 //
26 // G4QuadrupoleMagField implementation
27 //
28 // 03.02.1997, V.Grichine - Created
29 // 11.05.2012, B.Riese - Allow displaced origin and rotation
30 // -------------------------------------------------------------------
31
32 #include "G4QuadrupoleMagField.hh"
33 #include "G4RotationMatrix.hh"
34
35 namespace
36 {
37 G4RotationMatrix IdentityMatrix;
38 }
39
40 G4QuadrupoleMagField::G4QuadrupoleMagField(G4double pGradient)
41 {
42 fGradient = pGradient;
43 fpMatrix = &IdentityMatrix;
44 }
45
46 // -------------------------------------------------------------------
47
48 G4QuadrupoleMagField::G4QuadrupoleMagField(G4double pGradient,
49 const G4ThreeVector& pOrigin,
50 G4RotationMatrix* pMatrix)
51 {
52 fGradient = pGradient ;
53 fOrigin = pOrigin ;
54 fpMatrix = pMatrix ;
55 }
56
57 // -------------------------------------------------------------------
58
59 G4Field* G4QuadrupoleMagField::Clone() const
60 {
61 return new G4QuadrupoleMagField(fGradient, fOrigin, fpMatrix);
62 }
63
64 // -------------------------------------------------------------------
65
66 G4QuadrupoleMagField::~G4QuadrupoleMagField() = default;
67
68 // -------------------------------------------------------------------
69
70 void G4QuadrupoleMagField::GetFieldValue( const G4double y[], // [7]
71 G4double B[] ) const // [3]
72 {
73 // with displaced origin and rotation
74
75 G4ThreeVector r_global = G4ThreeVector(y[0] - fOrigin.x(),
76 y[1] - fOrigin.y(),
77 y[2] - fOrigin.z());
78
79 const G4ThreeVector r_local = (*fpMatrix) * r_global;
80 const G4ThreeVector B_local( fGradient * r_local.y(),
81 fGradient * r_local.x(), 0);
82 const G4ThreeVector B_global = fpMatrix->inverse() * B_local;
83
84 B[0] = B_global.x();
85 B[1] = B_global.y();
86 B[2] = B_global.z();
87 }
88