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25 // 25 //
26 // G4Mag_SpinEqRhs implementation <<
27 // 26 //
28 // Created: J.Apostolakis, P.Gumplinger - 08.0 << 27 // $Id: G4Mag_SpinEqRhs.cc,v 1.12 2006/06/29 18:24:39 gunter Exp $
>> 28 // GEANT4 tag $Name: geant4-08-03-patch-01 $
>> 29 //
>> 30 // This is the standard right-hand side for equation of motion.
>> 31 // This version of the right-hand side includes the three components
>> 32 // of the particle's spin.
>> 33 //
>> 34 // J. Apostolakis, February 8th, 1999
>> 35 // P. Gumplinger, February 8th, 1999
>> 36 // D. Cote-Ahern, P. Gumplinger, April 11th, 2001
>> 37 //
29 // ------------------------------------------- 38 // --------------------------------------------------------------------
30 39
31 #include "G4Mag_SpinEqRhs.hh" 40 #include "G4Mag_SpinEqRhs.hh"
32 #include "G4PhysicalConstants.hh" <<
33 #include "G4SystemOfUnits.hh" <<
34 #include "G4MagneticField.hh" 41 #include "G4MagneticField.hh"
35 #include "G4ThreeVector.hh" 42 #include "G4ThreeVector.hh"
36 43
37 G4Mag_SpinEqRhs::G4Mag_SpinEqRhs( G4MagneticFi 44 G4Mag_SpinEqRhs::G4Mag_SpinEqRhs( G4MagneticField* MagField )
38 : G4Mag_EqRhs( MagField ) << 45 : G4Mag_EqRhs( MagField )
39 { 46 {
>> 47 anomaly = 1.165923e-3;
40 } 48 }
41 49
42 G4Mag_SpinEqRhs::~G4Mag_SpinEqRhs() = default; << 50 G4Mag_SpinEqRhs::~G4Mag_SpinEqRhs() {}
43 51
44 void 52 void
45 G4Mag_SpinEqRhs::SetChargeMomentumMass(G4Charg << 53 G4Mag_SpinEqRhs::SetChargeMomentumMass(G4double particleCharge, // in e+ units
46 G4doubl 54 G4double MomentumXc,
47 G4doubl << 55 G4double mass)
48 { 56 {
49 G4Mag_EqRhs::SetChargeMomentumMass( particl << 57 // To set fCof_val
>> 58 G4Mag_EqRhs::SetChargeMomentumMass(particleCharge, MomentumXc, mass);
50 59
51 charge = particleCharge.GetCharge(); << 60 omegac = 0.105658387*GeV/mass * 2.837374841e-3*(rad/cm/kilogauss);
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 <<
60 G4double g_BMT; <<
61 if ( spin != 0. ) <<
62 { <<
63 g_BMT = (std::abs(magMoment)/muB)/spin; <<
64 } <<
65 else <<
66 { <<
67 g_BMT = 2.; <<
68 } <<
69 61
70 anomaly = (g_BMT - 2.)/2.; << 62 ParticleCharge = particleCharge;
71 63
72 G4double E = std::sqrt(sqr(MomentumXc)+sqr( << 64 E = std::sqrt(sqr(MomentumXc)+sqr(mass));
73 beta = MomentumXc/E; 65 beta = MomentumXc/E;
74 gamma = E/mass; 66 gamma = E/mass;
>> 67
75 } 68 }
76 69
77 void 70 void
78 G4Mag_SpinEqRhs::EvaluateRhsGivenB( const G4do 71 G4Mag_SpinEqRhs::EvaluateRhsGivenB( const G4double y[],
79 const G4do << 72 const G4double B[3],
80 G4do << 73 G4double dydx[] ) const
81 { 74 {
82 G4double momentum_mag_square = sqr(y[3]) + 75 G4double momentum_mag_square = sqr(y[3]) + sqr(y[4]) + sqr(y[5]);
83 G4double inv_momentum_magnitude = 1.0 / std 76 G4double inv_momentum_magnitude = 1.0 / std::sqrt( momentum_mag_square );
84 G4double cof = FCof()*inv_momentum_magnitud 77 G4double cof = FCof()*inv_momentum_magnitude;
85 78
86 dydx[0] = y[3] * inv_momentum_magnitude; 79 dydx[0] = y[3] * inv_momentum_magnitude; // (d/ds)x = Vx/V
87 dydx[1] = y[4] * inv_momentum_magnitude; 80 dydx[1] = y[4] * inv_momentum_magnitude; // (d/ds)y = Vy/V
88 dydx[2] = y[5] * inv_momentum_magnitude; 81 dydx[2] = y[5] * inv_momentum_magnitude; // (d/ds)z = Vz/V
89 << 82 dydx[3] = cof*(y[4]*B[2] - y[5]*B[1]) ; // Ax = a*(Vy*Bz - Vz*By)
90 if (charge == 0.) << 83 dydx[4] = cof*(y[5]*B[0] - y[3]*B[2]) ; // Ay = a*(Vz*Bx - Vx*Bz)
91 { << 84 dydx[5] = cof*(y[3]*B[1] - y[4]*B[0]) ; // Az = a*(Vx*By - Vy*Bx)
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 85
103 G4ThreeVector u(y[3], y[4], y[5]); 86 G4ThreeVector u(y[3], y[4], y[5]);
104 u *= inv_momentum_magnitude; 87 u *= inv_momentum_magnitude;
105 88
106 G4ThreeVector BField(B[0],B[1],B[2]); 89 G4ThreeVector BField(B[0],B[1],B[2]);
107 90
108 G4double udb = anomaly*beta*gamma/(1.+gamma 91 G4double udb = anomaly*beta*gamma/(1.+gamma) * (BField * u);
109 G4double ucb = (anomaly+1./gamma)/beta; 92 G4double ucb = (anomaly+1./gamma)/beta;
110 93
111 // Initialise the values of dydx that we do 94 // Initialise the values of dydx that we do not update.
112 dydx[6] = dydx[7] = dydx[8] = 0.0; 95 dydx[6] = dydx[7] = dydx[8] = 0.0;
113 96
114 G4ThreeVector Spin(y[9],y[10],y[11]); 97 G4ThreeVector Spin(y[9],y[10],y[11]);
>> 98 G4ThreeVector dSpin;
115 99
116 G4double pcharge; << 100 dSpin = ParticleCharge*omegac*(ucb*(Spin.cross(BField))-udb*(Spin.cross(u)));
117 if (charge == 0.) <<
118 { <<
119 pcharge = 1.; <<
120 } <<
121 else <<
122 { <<
123 pcharge = charge; <<
124 } <<
125 <<
126 G4ThreeVector dSpin(0.,0.,0.); <<
127 if (Spin.mag2() != 0.) <<
128 { <<
129 dSpin = pcharge*omegac*(ucb*(Spin.cross(B <<
130 } <<
131 101
132 dydx[9] = dSpin.x(); << 102 dydx[ 9] = dSpin.x();
133 dydx[10] = dSpin.y(); 103 dydx[10] = dSpin.y();
134 dydx[11] = dSpin.z(); 104 dydx[11] = dSpin.z();
135 105
136 return; << 106 return ;
137 } 107 }
138 108