1 | // |
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2 | // ******************************************************************** |
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3 | // * License and Disclaimer * |
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4 | // * * |
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5 | // * The Geant4 software is copyright of the Copyright Holders of * |
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6 | // * the Geant4 Collaboration. It is provided under the terms and * |
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7 | // * conditions of the Geant4 Software License, included in the file * |
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8 | // * LICENSE and available at http://cern.ch/geant4/license . These * |
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9 | // * include a list of copyright holders. * |
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10 | // * * |
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11 | // * Neither the authors of this software system, nor their employing * |
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12 | // * institutes,nor the agencies providing financial support for this * |
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13 | // * work make any representation or warranty, express or implied, * |
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14 | // * regarding this software system or assume any liability for its * |
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15 | // * use. Please see the license in the file LICENSE and URL above * |
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16 | // * for the full disclaimer and the limitation of liability. * |
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17 | // * * |
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18 | // * This code implementation is the result of the scientific and * |
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19 | // * technical work of the GEANT4 collaboration. * |
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20 | // * By using, copying, modifying or distributing the software (or * |
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21 | // * any work based on the software) you agree to acknowledge its * |
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22 | // * use in resulting scientific publications, and indicate your * |
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23 | // * acceptance of all terms of the Geant4 Software license. * |
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24 | // ******************************************************************** |
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25 | // |
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26 | // |
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27 | // $Id: G4Mag_SpinEqRhs.cc,v 1.15 2009/03/25 15:29:02 gcosmo Exp $ |
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28 | // GEANT4 tag $Name: $ |
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29 | // |
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30 | // This is the standard right-hand side for equation of motion. |
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31 | // This version of the right-hand side includes the three components |
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32 | // of the particle's spin. |
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33 | // |
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34 | // J. Apostolakis, February 8th, 1999 |
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35 | // P. Gumplinger, February 8th, 1999 |
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36 | // D. Cote-Ahern, P. Gumplinger, April 11th, 2001 |
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37 | // |
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38 | // -------------------------------------------------------------------- |
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39 | |
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40 | #include "G4Mag_SpinEqRhs.hh" |
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41 | #include "G4MagneticField.hh" |
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42 | #include "G4ThreeVector.hh" |
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43 | |
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44 | G4Mag_SpinEqRhs::G4Mag_SpinEqRhs( G4MagneticField* MagField ) |
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45 | : G4Mag_EqRhs( MagField ) |
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46 | { |
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47 | anomaly = 0.0011659208; |
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48 | } |
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49 | |
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50 | G4Mag_SpinEqRhs::~G4Mag_SpinEqRhs() |
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51 | { |
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52 | } |
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53 | |
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54 | void |
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55 | G4Mag_SpinEqRhs::SetChargeMomentumMass(G4double particleCharge, // in e+ units |
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56 | G4double MomentumXc, |
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57 | G4double particleMass) |
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58 | { |
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59 | // To set fCof_val |
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60 | G4Mag_EqRhs::SetChargeMomentumMass(particleCharge, MomentumXc, particleMass); |
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61 | |
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62 | omegac = 0.105658387*GeV/particleMass * 2.837374841e-3*(rad/cm/kilogauss); |
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63 | |
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64 | ParticleCharge = particleCharge; |
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65 | |
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66 | E = std::sqrt(sqr(MomentumXc)+sqr(particleMass)); |
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67 | beta = MomentumXc/E; |
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68 | gamma = E/particleMass; |
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69 | |
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70 | } |
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71 | |
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72 | void |
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73 | G4Mag_SpinEqRhs::EvaluateRhsGivenB( const G4double y[], |
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74 | const G4double B[3], |
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75 | G4double dydx[] ) const |
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76 | { |
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77 | G4double momentum_mag_square = sqr(y[3]) + sqr(y[4]) + sqr(y[5]); |
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78 | G4double inv_momentum_magnitude = 1.0 / std::sqrt( momentum_mag_square ); |
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79 | G4double cof = FCof()*inv_momentum_magnitude; |
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80 | |
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81 | dydx[0] = y[3] * inv_momentum_magnitude; // (d/ds)x = Vx/V |
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82 | dydx[1] = y[4] * inv_momentum_magnitude; // (d/ds)y = Vy/V |
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83 | dydx[2] = y[5] * inv_momentum_magnitude; // (d/ds)z = Vz/V |
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84 | dydx[3] = cof*(y[4]*B[2] - y[5]*B[1]) ; // Ax = a*(Vy*Bz - Vz*By) |
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85 | dydx[4] = cof*(y[5]*B[0] - y[3]*B[2]) ; // Ay = a*(Vz*Bx - Vx*Bz) |
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86 | dydx[5] = cof*(y[3]*B[1] - y[4]*B[0]) ; // Az = a*(Vx*By - Vy*Bx) |
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87 | |
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88 | G4ThreeVector u(y[3], y[4], y[5]); |
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89 | u *= inv_momentum_magnitude; |
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90 | |
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91 | G4ThreeVector BField(B[0],B[1],B[2]); |
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92 | |
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93 | G4double udb = anomaly*beta*gamma/(1.+gamma) * (BField * u); |
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94 | G4double ucb = (anomaly+1./gamma)/beta; |
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95 | |
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96 | // Initialise the values of dydx that we do not update. |
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97 | dydx[6] = dydx[7] = dydx[8] = 0.0; |
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98 | |
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99 | G4ThreeVector Spin(y[9],y[10],y[11]); |
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100 | |
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101 | G4ThreeVector dSpin; |
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102 | |
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103 | dSpin = ParticleCharge*omegac*(ucb*(Spin.cross(BField))-udb*(Spin.cross(u))); |
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104 | |
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105 | dydx[ 9] = dSpin.x(); |
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106 | dydx[10] = dSpin.y(); |
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107 | dydx[11] = dSpin.z(); |
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108 | |
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109 | return ; |
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110 | } |
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