| 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: G4EqEMFieldWithSpin.cc,v 1.4 2008/11/21 21:17:03 gum Exp $
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| 28 | // GEANT4 tag $Name: geant4-09-02-cand-01 $
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| 29 | //
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| 30 | //
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| 31 | // This is the standard right-hand side for equation of motion.
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| 32 | //
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| 33 | // The only case another is required is when using a moving reference
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| 34 | // frame ... or extending the class to include additional Forces,
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| 35 | // eg an electric field
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| 36 | //
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| 37 | // 30.08.2007 Chris Gong, Peter Gumplinger
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| 38 | //
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| 39 | // -------------------------------------------------------------------
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| 40 |
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| 41 | #include "G4EqEMFieldWithSpin.hh"
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| 42 | #include "G4ElectroMagneticField.hh"
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| 43 | #include "G4ThreeVector.hh"
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| 44 | #include "globals.hh"
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| 45 |
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| 46 | G4EqEMFieldWithSpin::G4EqEMFieldWithSpin(G4ElectroMagneticField *emField )
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| 47 | : G4EquationOfMotion( emField )
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| 48 | {
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| 49 | anomaly = 0.0011659208;
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| 50 | }
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| 51 |
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| 52 | G4EqEMFieldWithSpin::~G4EqEMFieldWithSpin()
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| 53 | {
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| 54 | }
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| 55 |
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| 56 | void
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| 57 | G4EqEMFieldWithSpin::SetChargeMomentumMass(G4double particleCharge, // e+ units
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| 58 | G4double MomentumXc,
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| 59 | G4double particleMass)
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| 60 | {
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| 61 | fElectroMagCof = eplus*particleCharge*c_light ;
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| 62 | fMassCof = particleMass*particleMass ;
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| 63 |
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| 64 | omegac = 0.105658387*GeV/particleMass * 2.837374841e-3*(rad/cm/kilogauss);
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| 65 |
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| 66 | ParticleCharge = particleCharge;
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| 67 |
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| 68 | E = std::sqrt(sqr(MomentumXc)+sqr(particleMass));
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| 69 | beta = MomentumXc/E;
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| 70 | gamma = E/particleMass;
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| 71 |
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| 72 | }
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| 73 |
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| 74 | void
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| 75 | G4EqEMFieldWithSpin::EvaluateRhsGivenB(const G4double y[],
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| 76 | const G4double Field[],
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| 77 | G4double dydx[] ) const
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| 78 | {
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| 79 |
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| 80 | // Components of y:
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| 81 | // 0-2 dr/ds,
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| 82 | // 3-5 dp/ds - momentum derivatives
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| 83 |
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| 84 | G4double pSquared = y[3]*y[3] + y[4]*y[4] + y[5]*y[5] ;
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| 85 |
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| 86 | G4double Energy = std::sqrt( pSquared + fMassCof );
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| 87 | G4double cof2 = Energy/c_light ;
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| 88 |
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| 89 | G4double pModuleInverse = 1.0/std::sqrt(pSquared) ;
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| 90 |
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| 91 | // G4double inverse_velocity = Energy * c_light * pModuleInverse;
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| 92 | G4double inverse_velocity = Energy * pModuleInverse / c_light;
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| 93 |
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| 94 | G4double cof1 = fElectroMagCof*pModuleInverse ;
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| 95 |
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| 96 | // G4double vDotE = y[3]*Field[3] + y[4]*Field[4] + y[5]*Field[5] ;
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| 97 |
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| 98 |
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| 99 | dydx[0] = y[3]*pModuleInverse ;
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| 100 | dydx[1] = y[4]*pModuleInverse ;
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| 101 | dydx[2] = y[5]*pModuleInverse ;
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| 102 |
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| 103 | dydx[3] = cof1*(cof2*Field[3] + (y[4]*Field[2] - y[5]*Field[1])) ;
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| 104 |
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| 105 | dydx[4] = cof1*(cof2*Field[4] + (y[5]*Field[0] - y[3]*Field[2])) ;
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| 106 |
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| 107 | dydx[5] = cof1*(cof2*Field[5] + (y[3]*Field[1] - y[4]*Field[0])) ;
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| 108 |
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| 109 | dydx[6] = dydx[8] = 0.;//not used
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| 110 |
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| 111 | // Lab Time of flight
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| 112 | dydx[7] = inverse_velocity;
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| 113 |
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| 114 | G4ThreeVector BField(Field[0],Field[1],Field[2]);
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| 115 |
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| 116 | G4ThreeVector u(y[3], y[4], y[5]);
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| 117 | u *= pModuleInverse;
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| 118 |
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| 119 | G4double udb = anomaly*beta*gamma/(1.+gamma) * (BField * u);
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| 120 | G4double ucb = (anomaly+1./gamma)/beta;
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| 121 |
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| 122 | G4ThreeVector Spin(y[9],y[10],y[11]);
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| 123 |
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| 124 | if (Spin.mag() > 0.) Spin = Spin.unit();
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| 125 |
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| 126 | G4ThreeVector dSpin;
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| 127 |
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| 128 | dSpin = ParticleCharge*omegac*(ucb*(Spin.cross(BField))-udb*(Spin.cross(u)));
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| 129 |
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| 130 | dydx[ 9] = dSpin.x();
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| 131 | dydx[10] = dSpin.y();
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| 132 | dydx[11] = dSpin.z();
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| 133 |
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| 134 | return ;
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| 135 | }
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