| Geant4 Cross Reference |
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25 // 2 //
26 // G4Mag_SpinEqRhs implementation << 3 // This is the standard right-hand side for equation of motion.
>> 4 // This version of the right-hand side includes
>> 5 // the three components of the particle's spin.
>> 6 //
>> 7 // J. Apostolakis, February 8th, 1999
>> 8 // P. Gumplinger, February 8th, 1999
27 // 9 //
28 // Created: J.Apostolakis, P.Gumplinger - 08.0 <<
29 // ------------------------------------------- <<
30 <<
31 #include "G4Mag_SpinEqRhs.hh" 10 #include "G4Mag_SpinEqRhs.hh"
32 #include "G4PhysicalConstants.hh" <<
33 #include "G4SystemOfUnits.hh" <<
34 #include "G4MagneticField.hh" <<
35 #include "G4ThreeVector.hh" 11 #include "G4ThreeVector.hh"
36 << 12 #include "globals.hh"
37 G4Mag_SpinEqRhs::G4Mag_SpinEqRhs( G4MagneticFi <<
38 : G4Mag_EqRhs( MagField ) <<
39 { <<
40 } <<
41 <<
42 G4Mag_SpinEqRhs::~G4Mag_SpinEqRhs() = default; <<
43 13
44 void 14 void
45 G4Mag_SpinEqRhs::SetChargeMomentumMass(G4Charg << 15 G4Mag_SpinEqRhs::SetChargeMomentumMass(G4double particleCharge, // in e+ units
46 G4doubl 16 G4double MomentumXc,
47 G4doubl << 17 G4double mass)
48 { 18 {
49 G4Mag_EqRhs::SetChargeMomentumMass( particl << 19 // To set fCof_val
50 << 20 G4Mag_EqRhs::SetChargeMomentumMass(particleCharge, MomentumXc, mass);
51 charge = particleCharge.GetCharge(); <<
52 mass = particleMass; <<
53 magMoment = particleCharge.GetMagneticDipol <<
54 spin = particleCharge.GetSpin(); <<
55 <<
56 omegac = (eplus/mass)*c_light; <<
57 <<
58 G4double muB = 0.5*eplus*hbar_Planck/(mass/ <<
59 21
60 G4double g_BMT; << 22 omegac = 0.105658387*GeV/mass * 2.837374841e-3*(rad/cm/kilogauss);
61 if ( spin != 0. ) << 23 anomaly = 1.165923e-3;
62 { << 24 ParticleCharge = particleCharge;
63 g_BMT = (std::abs(magMoment)/muB)/spin; <<
64 } <<
65 else <<
66 { <<
67 g_BMT = 2.; <<
68 } <<
69 <<
70 anomaly = (g_BMT - 2.)/2.; <<
71 25
72 G4double E = std::sqrt(sqr(MomentumXc)+sqr( << 26 // for testing only
73 beta = MomentumXc/E; << 27 anomaly = 0.0;
74 gamma = E/mass; <<
75 } 28 }
76 29
77 void 30 void
78 G4Mag_SpinEqRhs::EvaluateRhsGivenB( const G4do 31 G4Mag_SpinEqRhs::EvaluateRhsGivenB( const G4double y[],
79 const G4do << 32 const G4double B[3],
80 G4do << 33 G4double dydx[] ) const
81 { 34 {
82 G4double momentum_mag_square = sqr(y[3]) + << 35 G4double velocity_mag_square = sqr(y[3]) + sqr(y[4]) + sqr(y[5]);
83 G4double inv_momentum_magnitude = 1.0 / std << 36 G4double inv_velocity_magnitude = 1.0 / sqrt( velocity_mag_square );
84 G4double cof = FCof()*inv_momentum_magnitud <<
85 <<
86 dydx[0] = y[3] * inv_momentum_magnitude; <<
87 dydx[1] = y[4] * inv_momentum_magnitude; <<
88 dydx[2] = y[5] * inv_momentum_magnitude; <<
89 <<
90 if (charge == 0.) <<
91 { <<
92 dydx[3] = 0.; <<
93 dydx[4] = 0.; <<
94 dydx[5] = 0.; <<
95 } <<
96 else <<
97 { <<
98 dydx[3] = cof*(y[4]*B[2] - y[5]*B[1]) ; <<
99 dydx[4] = cof*(y[5]*B[0] - y[3]*B[2]) ; <<
100 dydx[5] = cof*(y[3]*B[1] - y[4]*B[0]) ; <<
101 } <<
102 37
103 G4ThreeVector u(y[3], y[4], y[5]); << 38 dydx[0] = y[3] * inv_velocity_magnitude; // (d/ds)x = Vx/V
104 u *= inv_momentum_magnitude; << 39 dydx[1] = y[4] * inv_velocity_magnitude; // (d/ds)y = Vy/V
>> 40 dydx[2] = y[5] * inv_velocity_magnitude; // (d/ds)z = Vz/V
>> 41 dydx[3] = FCof()*(y[4]*B[2] - y[5]*B[1]) ; // Ax = a*(Vy*Bz - Vz*By)
>> 42 dydx[4] = FCof()*(y[5]*B[0] - y[3]*B[2]) ; // Ay = a*(Vz*Bx - Vx*Bz)
>> 43 dydx[5] = FCof()*(y[3]*B[1] - y[4]*B[0]) ; // Az = a*(Vx*By - Vy*Bx)
>> 44
>> 45 G4double beta_squared = velocity_mag_square/c_squared;
>> 46 G4double beta = sqrt(beta_squared);
>> 47
>> 48 G4double gamma;
>> 49
>> 50 if (beta < 1.0){
>> 51 gamma = 1. / sqrt( 1. - beta_squared);
>> 52 } else {
>> 53 beta = 1.0;
>> 54 gamma = DBL_MAX;
>> 55 }
>> 56
>> 57 G4ThreeVector u;
>> 58 u.setX(inv_velocity_magnitude*y[3]);
>> 59 u.setY(inv_velocity_magnitude*y[4]);
>> 60 u.setZ(inv_velocity_magnitude*y[5]);
105 61
106 G4ThreeVector BField(B[0],B[1],B[2]); 62 G4ThreeVector BField(B[0],B[1],B[2]);
107 63
108 G4double udb = anomaly*beta*gamma/(1.+gamma 64 G4double udb = anomaly*beta*gamma/(1.+gamma) * (BField * u);
109 G4double ucb = (anomaly+1./gamma)/beta; 65 G4double ucb = (anomaly+1./gamma)/beta;
110 66
111 // Initialise the values of dydx that we do <<
112 dydx[6] = dydx[7] = dydx[8] = 0.0; <<
113 <<
114 G4ThreeVector Spin(y[9],y[10],y[11]); 67 G4ThreeVector Spin(y[9],y[10],y[11]);
115 68
116 G4double pcharge; << 69 G4ThreeVector dSpin;
117 if (charge == 0.) <<
118 { <<
119 pcharge = 1.; <<
120 } <<
121 else <<
122 { <<
123 pcharge = charge; <<
124 } <<
125 70
126 G4ThreeVector dSpin(0.,0.,0.); << 71 dSpin = ParticleCharge*omegac*(ucb*(Spin.cross(BField))-udb*(Spin.cross(u)));
127 if (Spin.mag2() != 0.) <<
128 { <<
129 dSpin = pcharge*omegac*(ucb*(Spin.cross(B <<
130 } <<
131 72
132 dydx[9] = dSpin.x(); << 73 dydx[ 9] = dSpin.x();
133 dydx[10] = dSpin.y(); 74 dydx[10] = dSpin.y();
134 dydx[11] = dSpin.z(); 75 dydx[11] = dSpin.z();
135 76
136 return; << 77 return ;
137 } 78 }
138 79