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25 // 25 //
26 // G4EqEMFieldWithSpin implementation <<
27 // 26 //
28 // Created: Chris Gong & Peter Gumplinger, 30. << 27 // $Id: G4EqEMFieldWithSpin.cc,v 1.1.2.1 2008/04/24 12:43:57 gcosmo Exp $
>> 28 // GEANT4 tag $Name: geant4-09-01-patch-03 $
>> 29 //
>> 30 //
>> 31 // This is the standard right-hand side for equation of motion.
>> 32 //
>> 33 // The only case another is required is when using a moving reference
>> 34 // frame ... or extending the class to include additional Forces,
>> 35 // eg an electric field
>> 36 //
>> 37 // 30.08.2007 Chris Gong, Peter Gumplinger
>> 38 //
29 // ------------------------------------------- 39 // -------------------------------------------------------------------
30 40
31 #include "G4EqEMFieldWithSpin.hh" 41 #include "G4EqEMFieldWithSpin.hh"
32 #include "G4ElectroMagneticField.hh" <<
33 #include "G4ThreeVector.hh" 42 #include "G4ThreeVector.hh"
34 #include "globals.hh" 43 #include "globals.hh"
35 #include "G4PhysicalConstants.hh" <<
36 #include "G4SystemOfUnits.hh" <<
37 44
38 G4EqEMFieldWithSpin::G4EqEMFieldWithSpin(G4Ele 45 G4EqEMFieldWithSpin::G4EqEMFieldWithSpin(G4ElectroMagneticField *emField )
39 : G4EquationOfMotion( emField ) << 46 : G4EquationOfMotion( emField ) { anomaly = 1.165923e-3; }
40 { <<
41 } <<
42 <<
43 G4EqEMFieldWithSpin::~G4EqEMFieldWithSpin() = <<
44 47
45 void 48 void
46 G4EqEMFieldWithSpin::SetChargeMomentumMass(G4C << 49 G4EqEMFieldWithSpin::SetChargeMomentumMass(G4double particleCharge, // e+ units
47 G4d << 50 G4double MomentumXc,
48 G4d << 51 G4double particleMass)
49 { 52 {
50 charge = particleCharge.GetCharge(); << 53 fElectroMagCof = eplus*particleCharge*c_light ;
51 mass = particleMass; << 54 fMassCof = particleMass*particleMass ;
52 magMoment = particleCharge.GetMagneticDipol << 55
53 spin = particleCharge.GetSpin(); << 56 omegac = 0.105658387*GeV/particleMass * 2.837374841e-3*(rad/cm/kilogauss);
54 <<
55 fElectroMagCof = eplus*charge*c_light ; <<
56 fMassCof = mass*mass; <<
57 <<
58 omegac = (eplus/mass)*c_light; <<
59 <<
60 G4double muB = 0.5*eplus*hbar_Planck/(mass/ <<
61 <<
62 G4double g_BMT; <<
63 if ( spin != 0. ) <<
64 { <<
65 g_BMT = (std::abs(magMoment)/muB)/spin; <<
66 } <<
67 else <<
68 { <<
69 g_BMT = 2.; <<
70 } <<
71 57
72 anomaly = (g_BMT - 2.)/2.; << 58 ParticleCharge = particleCharge;
73 59
74 G4double E = std::sqrt(sqr(MomentumXc)+sqr( << 60 E = std::sqrt(sqr(MomentumXc)+sqr(particleMass));
75 beta = MomentumXc/E; 61 beta = MomentumXc/E;
76 gamma = E/mass; << 62 gamma = E/particleMass;
77 } 63 }
78 64
>> 65
>> 66
79 void 67 void
80 G4EqEMFieldWithSpin::EvaluateRhsGivenB(const G 68 G4EqEMFieldWithSpin::EvaluateRhsGivenB(const G4double y[],
81 const G << 69 const G4double Field[],
82 G << 70 G4double dydx[] ) const
83 { 71 {
84 72
85 // Components of y: 73 // Components of y:
86 // 0-2 dr/ds, << 74 // 0-2 dr/ds,
87 // 3-5 dp/ds - momentum derivatives << 75 // 3-5 dp/ds - momentum derivatives
88 // 9-11 dSpin/ds = (1/beta) dSpin/dt - s <<
89 <<
90 // The BMT equation, following J.D.Jackson, <<
91 // Electrodynamics, Second Edition, <<
92 // dS/dt = (e/mc) S \cross <<
93 // [ (g/2-1 +1/\gamma) B <<
94 // -(g/2-1)\gamma/(\gamma+1) <<
95 // -(g/2-\gamma/(\gamma+1) \b <<
96 // where <<
97 // S = \vec{s}, where S^2 = 1 <<
98 // B = \vec{B} <<
99 // \beta = \vec{\beta} = \beta \vec{u} with <<
100 // E = \vec{E} <<
101 76
102 G4double pSquared = y[3]*y[3] + y[4]*y[4] + 77 G4double pSquared = y[3]*y[3] + y[4]*y[4] + y[5]*y[5] ;
103 78
104 G4double Energy = std::sqrt( pSquared + f 79 G4double Energy = std::sqrt( pSquared + fMassCof );
105 G4double cof2 = Energy/c_light ; 80 G4double cof2 = Energy/c_light ;
106 81
107 G4double pModuleInverse = 1.0/std::sqrt(pS 82 G4double pModuleInverse = 1.0/std::sqrt(pSquared) ;
108 83
>> 84 // G4double inverse_velocity = Energy * c_light * pModuleInverse;
109 G4double inverse_velocity = Energy * pModul 85 G4double inverse_velocity = Energy * pModuleInverse / c_light;
110 86
111 G4double cof1 = fElectroMagCof*pModuleInver << 87 G4double cof1 = fElectroMagCof*pModuleInverse ;
>> 88
>> 89 // G4double vDotE = y[3]*Field[3] + y[4]*Field[4] + y[5]*Field[5] ;
>> 90
112 91
113 dydx[0] = y[3]*pModuleInverse ; 92 dydx[0] = y[3]*pModuleInverse ;
114 dydx[1] = y[4]*pModuleInverse ; 93 dydx[1] = y[4]*pModuleInverse ;
115 dydx[2] = y[5]*pModuleInverse ; 94 dydx[2] = y[5]*pModuleInverse ;
116 95
117 dydx[3] = cof1*(cof2*Field[3] + (y[4]*Field 96 dydx[3] = cof1*(cof2*Field[3] + (y[4]*Field[2] - y[5]*Field[1])) ;
118 97
119 dydx[4] = cof1*(cof2*Field[4] + (y[5]*Field 98 dydx[4] = cof1*(cof2*Field[4] + (y[5]*Field[0] - y[3]*Field[2])) ;
120 99
121 dydx[5] = cof1*(cof2*Field[5] + (y[3]*Field 100 dydx[5] = cof1*(cof2*Field[5] + (y[3]*Field[1] - y[4]*Field[0])) ;
122 101
123 dydx[6] = dydx[8] = 0.;//not used 102 dydx[6] = dydx[8] = 0.;//not used
124 103
125 // Lab Time of flight 104 // Lab Time of flight
126 dydx[7] = inverse_velocity; 105 dydx[7] = inverse_velocity;
127 106
128 G4ThreeVector BField(Field[0],Field[1],Fiel 107 G4ThreeVector BField(Field[0],Field[1],Field[2]);
129 G4ThreeVector EField(Field[3],Field[4],Fiel <<
130 <<
131 EField /= c_light; <<
132 108
133 G4ThreeVector u(y[3], y[4], y[5]); 109 G4ThreeVector u(y[3], y[4], y[5]);
134 u *= pModuleInverse; 110 u *= pModuleInverse;
135 111
136 G4double udb = anomaly*beta*gamma/(1.+gamma 112 G4double udb = anomaly*beta*gamma/(1.+gamma) * (BField * u);
137 G4double ucb = (anomaly+1./gamma)/beta; 113 G4double ucb = (anomaly+1./gamma)/beta;
138 G4double uce = anomaly + 1./(gamma+1.); <<
139 114
140 G4ThreeVector Spin(y[9],y[10],y[11]); 115 G4ThreeVector Spin(y[9],y[10],y[11]);
>> 116 G4ThreeVector dSpin;
141 117
142 G4double pcharge; << 118 dSpin = ParticleCharge*omegac*(ucb*(Spin.cross(BField))-udb*(Spin.cross(u)));
143 if (charge == 0.) <<
144 { <<
145 pcharge = 1.; <<
146 } <<
147 else <<
148 { <<
149 pcharge = charge; <<
150 } <<
151 <<
152 G4ThreeVector dSpin(0.,0.,0.); <<
153 if (Spin.mag2() != 0.) <<
154 { <<
155 dSpin = pcharge*omegac*( ucb*(Spin.cross <<
156 // from Jackson <<
157 // -uce*Spin.cross( <<
158 // but this form ha <<
159 - uce*(u*(Spin*EField) - <<
160 } <<
161 119
162 dydx[ 9] = dSpin.x(); 120 dydx[ 9] = dSpin.x();
163 dydx[10] = dSpin.y(); 121 dydx[10] = dSpin.y();
164 dydx[11] = dSpin.z(); 122 dydx[11] = dSpin.z();
165 123
166 return; << 124 return ;
167 } 125 }
168 126