| Geant4 Cross Reference |
1 // 1 //
2 // ******************************************* 2 // ********************************************************************
3 // * License and Disclaimer 3 // * License and Disclaimer *
4 // * 4 // * *
5 // * The Geant4 software is copyright of th 5 // * The Geant4 software is copyright of the Copyright Holders of *
6 // * the Geant4 Collaboration. It is provided 6 // * the Geant4 Collaboration. It is provided under the terms and *
7 // * conditions of the Geant4 Software License 7 // * conditions of the Geant4 Software License, included in the file *
8 // * LICENSE and available at http://cern.ch/ 8 // * LICENSE and available at http://cern.ch/geant4/license . These *
9 // * include a list of copyright holders. 9 // * include a list of copyright holders. *
10 // * 10 // * *
11 // * Neither the authors of this software syst 11 // * Neither the authors of this software system, nor their employing *
12 // * institutes,nor the agencies providing fin 12 // * institutes,nor the agencies providing financial support for this *
13 // * work make any representation or warran 13 // * work make any representation or warranty, express or implied, *
14 // * regarding this software system or assum 14 // * regarding this software system or assume any liability for its *
15 // * use. Please see the license in the file 15 // * use. Please see the license in the file LICENSE and URL above *
16 // * for the full disclaimer and the limitatio 16 // * for the full disclaimer and the limitation of liability. *
17 // * 17 // * *
18 // * This code implementation is the result 18 // * This code implementation is the result of the scientific and *
19 // * technical work of the GEANT4 collaboratio 19 // * technical work of the GEANT4 collaboration. *
20 // * By using, copying, modifying or distri 20 // * By using, copying, modifying or distributing the software (or *
21 // * any work based on the software) you ag 21 // * any work based on the software) you agree to acknowledge its *
22 // * use in resulting scientific publicati 22 // * use in resulting scientific publications, and indicate your *
23 // * acceptance of all terms of the Geant4 Sof 23 // * acceptance of all terms of the Geant4 Software license. *
24 // ******************************************* 24 // ********************************************************************
25 // 25 //
26 // G4EqEMFieldWithSpin implementation <<
27 // 26 //
28 // Created: Chris Gong & Peter Gumplinger, 30. << 27 //
>> 28 //
>> 29 // This is the standard right-hand side for equation of motion.
>> 30 //
>> 31 // 30.08.2007 Chris Gong, Peter Gumplinger
>> 32 // 14.02.2009 Kevin Lynch
>> 33 // 06.11.2009 Hiromi Iinuma
>> 34 //
29 // ------------------------------------------- 35 // -------------------------------------------------------------------
30 36
31 #include "G4EqEMFieldWithSpin.hh" 37 #include "G4EqEMFieldWithSpin.hh"
32 #include "G4ElectroMagneticField.hh" 38 #include "G4ElectroMagneticField.hh"
33 #include "G4ThreeVector.hh" 39 #include "G4ThreeVector.hh"
34 #include "globals.hh" 40 #include "globals.hh"
35 #include "G4PhysicalConstants.hh" 41 #include "G4PhysicalConstants.hh"
36 #include "G4SystemOfUnits.hh" 42 #include "G4SystemOfUnits.hh"
37 43
38 G4EqEMFieldWithSpin::G4EqEMFieldWithSpin(G4Ele 44 G4EqEMFieldWithSpin::G4EqEMFieldWithSpin(G4ElectroMagneticField *emField )
39 : G4EquationOfMotion( emField ) << 45 : G4EquationOfMotion( emField ), charge(0.), mass(0.), magMoment(0.),
>> 46 spin(0.), fElectroMagCof(0.), fMassCof(0.), omegac(0.),
>> 47 anomaly(0.0011659208), beta(0.), gamma(0.)
40 { 48 {
41 } 49 }
42 50
43 G4EqEMFieldWithSpin::~G4EqEMFieldWithSpin() = << 51 G4EqEMFieldWithSpin::~G4EqEMFieldWithSpin()
>> 52 {
>> 53 }
44 54
45 void 55 void
46 G4EqEMFieldWithSpin::SetChargeMomentumMass(G4C 56 G4EqEMFieldWithSpin::SetChargeMomentumMass(G4ChargeState particleCharge,
47 G4d << 57 G4double MomentumXc,
48 G4d << 58 G4double particleMass)
49 { 59 {
50 charge = particleCharge.GetCharge(); 60 charge = particleCharge.GetCharge();
51 mass = particleMass; 61 mass = particleMass;
52 magMoment = particleCharge.GetMagneticDipol 62 magMoment = particleCharge.GetMagneticDipoleMoment();
53 spin = particleCharge.GetSpin(); 63 spin = particleCharge.GetSpin();
54 64
55 fElectroMagCof = eplus*charge*c_light ; 65 fElectroMagCof = eplus*charge*c_light ;
56 fMassCof = mass*mass; 66 fMassCof = mass*mass;
57 67
58 omegac = (eplus/mass)*c_light; 68 omegac = (eplus/mass)*c_light;
59 69
60 G4double muB = 0.5*eplus*hbar_Planck/(mass/ 70 G4double muB = 0.5*eplus*hbar_Planck/(mass/c_squared);
61 71
62 G4double g_BMT; 72 G4double g_BMT;
63 if ( spin != 0. ) << 73 if ( spin != 0. ) g_BMT = (std::abs(magMoment)/muB)/spin;
64 { << 74 else g_BMT = 2.;
65 g_BMT = (std::abs(magMoment)/muB)/spin; <<
66 } <<
67 else <<
68 { <<
69 g_BMT = 2.; <<
70 } <<
71 75
72 anomaly = (g_BMT - 2.)/2.; 76 anomaly = (g_BMT - 2.)/2.;
73 77
74 G4double E = std::sqrt(sqr(MomentumXc)+sqr( 78 G4double E = std::sqrt(sqr(MomentumXc)+sqr(mass));
75 beta = MomentumXc/E; 79 beta = MomentumXc/E;
76 gamma = E/mass; 80 gamma = E/mass;
77 } 81 }
78 82
79 void 83 void
80 G4EqEMFieldWithSpin::EvaluateRhsGivenB(const G 84 G4EqEMFieldWithSpin::EvaluateRhsGivenB(const G4double y[],
81 const G 85 const G4double Field[],
82 G 86 G4double dydx[] ) const
83 { 87 {
84 88
85 // Components of y: 89 // Components of y:
86 // 0-2 dr/ds, 90 // 0-2 dr/ds,
87 // 3-5 dp/ds - momentum derivatives 91 // 3-5 dp/ds - momentum derivatives
88 // 9-11 dSpin/ds = (1/beta) dSpin/dt - s 92 // 9-11 dSpin/ds = (1/beta) dSpin/dt - spin derivatives
89 93
90 // The BMT equation, following J.D.Jackson, 94 // The BMT equation, following J.D.Jackson, Classical
91 // Electrodynamics, Second Edition, 95 // Electrodynamics, Second Edition,
92 // dS/dt = (e/mc) S \cross 96 // dS/dt = (e/mc) S \cross
93 // [ (g/2-1 +1/\gamma) B 97 // [ (g/2-1 +1/\gamma) B
94 // -(g/2-1)\gamma/(\gamma+1) 98 // -(g/2-1)\gamma/(\gamma+1) (\beta \cdot B)\beta
95 // -(g/2-\gamma/(\gamma+1) \b 99 // -(g/2-\gamma/(\gamma+1) \beta \cross E ]
96 // where 100 // where
97 // S = \vec{s}, where S^2 = 1 101 // S = \vec{s}, where S^2 = 1
98 // B = \vec{B} 102 // B = \vec{B}
99 // \beta = \vec{\beta} = \beta \vec{u} with 103 // \beta = \vec{\beta} = \beta \vec{u} with u^2 = 1
100 // E = \vec{E} 104 // E = \vec{E}
101 105
102 G4double pSquared = y[3]*y[3] + y[4]*y[4] + 106 G4double pSquared = y[3]*y[3] + y[4]*y[4] + y[5]*y[5] ;
103 107
104 G4double Energy = std::sqrt( pSquared + f 108 G4double Energy = std::sqrt( pSquared + fMassCof );
105 G4double cof2 = Energy/c_light ; 109 G4double cof2 = Energy/c_light ;
106 110
107 G4double pModuleInverse = 1.0/std::sqrt(pS 111 G4double pModuleInverse = 1.0/std::sqrt(pSquared) ;
108 112
109 G4double inverse_velocity = Energy * pModul 113 G4double inverse_velocity = Energy * pModuleInverse / c_light;
110 114
111 G4double cof1 = fElectroMagCof*pModuleInver << 115 G4double cof1 = fElectroMagCof*pModuleInverse ;
112 116
113 dydx[0] = y[3]*pModuleInverse ; 117 dydx[0] = y[3]*pModuleInverse ;
114 dydx[1] = y[4]*pModuleInverse ; 118 dydx[1] = y[4]*pModuleInverse ;
115 dydx[2] = y[5]*pModuleInverse ; 119 dydx[2] = y[5]*pModuleInverse ;
116 120
117 dydx[3] = cof1*(cof2*Field[3] + (y[4]*Field 121 dydx[3] = cof1*(cof2*Field[3] + (y[4]*Field[2] - y[5]*Field[1])) ;
118 122
119 dydx[4] = cof1*(cof2*Field[4] + (y[5]*Field 123 dydx[4] = cof1*(cof2*Field[4] + (y[5]*Field[0] - y[3]*Field[2])) ;
120 124
121 dydx[5] = cof1*(cof2*Field[5] + (y[3]*Field 125 dydx[5] = cof1*(cof2*Field[5] + (y[3]*Field[1] - y[4]*Field[0])) ;
122 126
123 dydx[6] = dydx[8] = 0.;//not used 127 dydx[6] = dydx[8] = 0.;//not used
124 128
125 // Lab Time of flight 129 // Lab Time of flight
126 dydx[7] = inverse_velocity; 130 dydx[7] = inverse_velocity;
127 131
128 G4ThreeVector BField(Field[0],Field[1],Fiel 132 G4ThreeVector BField(Field[0],Field[1],Field[2]);
129 G4ThreeVector EField(Field[3],Field[4],Fiel 133 G4ThreeVector EField(Field[3],Field[4],Field[5]);
130 134
131 EField /= c_light; 135 EField /= c_light;
132 136
133 G4ThreeVector u(y[3], y[4], y[5]); 137 G4ThreeVector u(y[3], y[4], y[5]);
134 u *= pModuleInverse; 138 u *= pModuleInverse;
135 139
136 G4double udb = anomaly*beta*gamma/(1.+gamma 140 G4double udb = anomaly*beta*gamma/(1.+gamma) * (BField * u);
137 G4double ucb = (anomaly+1./gamma)/beta; 141 G4double ucb = (anomaly+1./gamma)/beta;
138 G4double uce = anomaly + 1./(gamma+1.); 142 G4double uce = anomaly + 1./(gamma+1.);
139 143
140 G4ThreeVector Spin(y[9],y[10],y[11]); 144 G4ThreeVector Spin(y[9],y[10],y[11]);
141 145
142 G4double pcharge; 146 G4double pcharge;
143 if (charge == 0.) << 147 if (charge == 0.) pcharge = 1.;
144 { << 148 else pcharge = charge;
145 pcharge = 1.; <<
146 } <<
147 else <<
148 { <<
149 pcharge = charge; <<
150 } <<
151 149
152 G4ThreeVector dSpin(0.,0.,0.); 150 G4ThreeVector dSpin(0.,0.,0.);
153 if (Spin.mag2() != 0.) << 151 if (Spin.mag2() != 0.) {
154 { << 152 dSpin =
155 dSpin = pcharge*omegac*( ucb*(Spin.cross << 153 pcharge*omegac*( ucb*(Spin.cross(BField))-udb*(Spin.cross(u))
156 // from Jackson 154 // from Jackson
157 // -uce*Spin.cross( 155 // -uce*Spin.cross(u.cross(EField)) );
158 // but this form ha 156 // but this form has one less operation
159 - uce*(u*(Spin*EField) - 157 - uce*(u*(Spin*EField) - EField*(Spin*u)) );
160 } 158 }
161 159
162 dydx[ 9] = dSpin.x(); 160 dydx[ 9] = dSpin.x();
163 dydx[10] = dSpin.y(); 161 dydx[10] = dSpin.y();
164 dydx[11] = dSpin.z(); 162 dydx[11] = dSpin.z();
165 163
166 return; << 164 return ;
167 } 165 }
168 166