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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 78728 2014-01-20 12:57:20Z gcosmo $
>> 28 //
>> 29 // This is the standard right-hand side for equation of motion.
>> 30 // This version of the right-hand side includes the three components
>> 31 // of the particle's spin.
>> 32 //
>> 33 // J. Apostolakis, February 8th, 1999
>> 34 // P. Gumplinger, February 8th, 1999
>> 35 // D. Cote-Ahern, P. Gumplinger, April 11th, 2001
>> 36 //
29 // ------------------------------------------- 37 // --------------------------------------------------------------------
30 38
31 #include "G4Mag_SpinEqRhs.hh" 39 #include "G4Mag_SpinEqRhs.hh"
32 #include "G4PhysicalConstants.hh" 40 #include "G4PhysicalConstants.hh"
33 #include "G4SystemOfUnits.hh" 41 #include "G4SystemOfUnits.hh"
34 #include "G4MagneticField.hh" 42 #include "G4MagneticField.hh"
35 #include "G4ThreeVector.hh" 43 #include "G4ThreeVector.hh"
36 44
37 G4Mag_SpinEqRhs::G4Mag_SpinEqRhs( G4MagneticFi 45 G4Mag_SpinEqRhs::G4Mag_SpinEqRhs( G4MagneticField* MagField )
38 : G4Mag_EqRhs( MagField ) << 46 : G4Mag_EqRhs( MagField ), charge(0.), mass(0.), magMoment(0.),
>> 47 spin(0.), omegac(0.), anomaly(0.0011659208), beta(0.), gamma(0.)
39 { 48 {
40 } 49 }
41 50
42 G4Mag_SpinEqRhs::~G4Mag_SpinEqRhs() = default; << 51 G4Mag_SpinEqRhs::~G4Mag_SpinEqRhs()
>> 52 {
>> 53 }
43 54
44 void 55 void
45 G4Mag_SpinEqRhs::SetChargeMomentumMass(G4Charg 56 G4Mag_SpinEqRhs::SetChargeMomentumMass(G4ChargeState particleCharge,
46 G4doubl 57 G4double MomentumXc,
47 G4doubl 58 G4double particleMass)
48 { 59 {
49 G4Mag_EqRhs::SetChargeMomentumMass( particl 60 G4Mag_EqRhs::SetChargeMomentumMass( particleCharge, MomentumXc, mass);
50 61
51 charge = particleCharge.GetCharge(); 62 charge = particleCharge.GetCharge();
52 mass = particleMass; 63 mass = particleMass;
53 magMoment = particleCharge.GetMagneticDipol 64 magMoment = particleCharge.GetMagneticDipoleMoment();
54 spin = particleCharge.GetSpin(); 65 spin = particleCharge.GetSpin();
55 66
56 omegac = (eplus/mass)*c_light; 67 omegac = (eplus/mass)*c_light;
57 68
58 G4double muB = 0.5*eplus*hbar_Planck/(mass/ 69 G4double muB = 0.5*eplus*hbar_Planck/(mass/c_squared);
59 70
60 G4double g_BMT; 71 G4double g_BMT;
61 if ( spin != 0. ) << 72 if ( spin != 0. ) g_BMT = (magMoment/muB)/spin;
62 { << 73 else g_BMT = 2.;
63 g_BMT = (std::abs(magMoment)/muB)/spin; <<
64 } <<
65 else <<
66 { <<
67 g_BMT = 2.; <<
68 } <<
69 74
70 anomaly = (g_BMT - 2.)/2.; 75 anomaly = (g_BMT - 2.)/2.;
71 76
72 G4double E = std::sqrt(sqr(MomentumXc)+sqr( 77 G4double E = std::sqrt(sqr(MomentumXc)+sqr(mass));
73 beta = MomentumXc/E; 78 beta = MomentumXc/E;
74 gamma = E/mass; 79 gamma = E/mass;
75 } 80 }
76 81
77 void 82 void
78 G4Mag_SpinEqRhs::EvaluateRhsGivenB( const G4do 83 G4Mag_SpinEqRhs::EvaluateRhsGivenB( const G4double y[],
79 const G4do 84 const G4double B[3],
80 G4do 85 G4double dydx[] ) const
81 { 86 {
82 G4double momentum_mag_square = sqr(y[3]) + 87 G4double momentum_mag_square = sqr(y[3]) + sqr(y[4]) + sqr(y[5]);
83 G4double inv_momentum_magnitude = 1.0 / std 88 G4double inv_momentum_magnitude = 1.0 / std::sqrt( momentum_mag_square );
84 G4double cof = FCof()*inv_momentum_magnitud 89 G4double cof = FCof()*inv_momentum_magnitude;
85 90
86 dydx[0] = y[3] * inv_momentum_magnitude; 91 dydx[0] = y[3] * inv_momentum_magnitude; // (d/ds)x = Vx/V
87 dydx[1] = y[4] * inv_momentum_magnitude; 92 dydx[1] = y[4] * inv_momentum_magnitude; // (d/ds)y = Vy/V
88 dydx[2] = y[5] * inv_momentum_magnitude; 93 dydx[2] = y[5] * inv_momentum_magnitude; // (d/ds)z = Vz/V
89 94
90 if (charge == 0.) << 95 if (charge == 0.) {
91 { <<
92 dydx[3] = 0.; 96 dydx[3] = 0.;
93 dydx[4] = 0.; 97 dydx[4] = 0.;
94 dydx[5] = 0.; 98 dydx[5] = 0.;
95 } << 99 } else {
96 else <<
97 { <<
98 dydx[3] = cof*(y[4]*B[2] - y[5]*B[1]) ; 100 dydx[3] = cof*(y[4]*B[2] - y[5]*B[1]) ; // Ax = a*(Vy*Bz - Vz*By)
99 dydx[4] = cof*(y[5]*B[0] - y[3]*B[2]) ; 101 dydx[4] = cof*(y[5]*B[0] - y[3]*B[2]) ; // Ay = a*(Vz*Bx - Vx*Bz)
100 dydx[5] = cof*(y[3]*B[1] - y[4]*B[0]) ; 102 dydx[5] = cof*(y[3]*B[1] - y[4]*B[0]) ; // Az = a*(Vx*By - Vy*Bx)
101 } 103 }
102 104
103 G4ThreeVector u(y[3], y[4], y[5]); 105 G4ThreeVector u(y[3], y[4], y[5]);
104 u *= inv_momentum_magnitude; 106 u *= inv_momentum_magnitude;
105 107
106 G4ThreeVector BField(B[0],B[1],B[2]); 108 G4ThreeVector BField(B[0],B[1],B[2]);
107 109
108 G4double udb = anomaly*beta*gamma/(1.+gamma 110 G4double udb = anomaly*beta*gamma/(1.+gamma) * (BField * u);
109 G4double ucb = (anomaly+1./gamma)/beta; 111 G4double ucb = (anomaly+1./gamma)/beta;
110 112
111 // Initialise the values of dydx that we do 113 // Initialise the values of dydx that we do not update.
112 dydx[6] = dydx[7] = dydx[8] = 0.0; 114 dydx[6] = dydx[7] = dydx[8] = 0.0;
113 115
114 G4ThreeVector Spin(y[9],y[10],y[11]); 116 G4ThreeVector Spin(y[9],y[10],y[11]);
115 117
116 G4double pcharge; 118 G4double pcharge;
117 if (charge == 0.) << 119 if (charge == 0.) pcharge = 1.;
118 { << 120 else pcharge = charge;
119 pcharge = 1.; <<
120 } <<
121 else <<
122 { <<
123 pcharge = charge; <<
124 } <<
125 121
126 G4ThreeVector dSpin(0.,0.,0.); 122 G4ThreeVector dSpin(0.,0.,0.);
127 if (Spin.mag2() != 0.) << 123 if (Spin.mag2() != 0.) {
128 { << 124 dSpin = pcharge*omegac*(ucb*(Spin.cross(BField))-udb*(Spin.cross(u)));
129 dSpin = pcharge*omegac*(ucb*(Spin.cross(B <<
130 } 125 }
131 126
132 dydx[9] = dSpin.x(); << 127 dydx[ 9] = dSpin.x();
133 dydx[10] = dSpin.y(); 128 dydx[10] = dSpin.y();
134 dydx[11] = dSpin.z(); 129 dydx[11] = dSpin.z();
135 130
136 return; << 131 return ;
137 } 132 }
138 133