[831] | 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 1.12 2006/06/29 18:24:39 gunter Exp $ |
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[850] | 28 | // GEANT4 tag $Name: HEAD $ |
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[831] | 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 = 1.165923e-3; |
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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 | void |
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| 53 | G4Mag_SpinEqRhs::SetChargeMomentumMass(G4double particleCharge, // in e+ units |
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| 54 | G4double MomentumXc, |
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| 55 | G4double mass) |
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| 56 | { |
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| 57 | // To set fCof_val |
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| 58 | G4Mag_EqRhs::SetChargeMomentumMass(particleCharge, MomentumXc, mass); |
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| 59 | |
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| 60 | omegac = 0.105658387*GeV/mass * 2.837374841e-3*(rad/cm/kilogauss); |
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| 61 | |
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| 62 | ParticleCharge = particleCharge; |
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| 63 | |
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| 64 | E = std::sqrt(sqr(MomentumXc)+sqr(mass)); |
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| 65 | beta = MomentumXc/E; |
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| 66 | gamma = E/mass; |
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| 67 | |
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| 68 | } |
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| 69 | |
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| 70 | void |
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| 71 | G4Mag_SpinEqRhs::EvaluateRhsGivenB( const G4double y[], |
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| 72 | const G4double B[3], |
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| 73 | G4double dydx[] ) const |
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| 74 | { |
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| 75 | G4double momentum_mag_square = sqr(y[3]) + sqr(y[4]) + sqr(y[5]); |
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| 76 | G4double inv_momentum_magnitude = 1.0 / std::sqrt( momentum_mag_square ); |
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| 77 | G4double cof = FCof()*inv_momentum_magnitude; |
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| 78 | |
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| 79 | dydx[0] = y[3] * inv_momentum_magnitude; // (d/ds)x = Vx/V |
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| 80 | dydx[1] = y[4] * inv_momentum_magnitude; // (d/ds)y = Vy/V |
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| 81 | dydx[2] = y[5] * inv_momentum_magnitude; // (d/ds)z = Vz/V |
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| 82 | dydx[3] = cof*(y[4]*B[2] - y[5]*B[1]) ; // Ax = a*(Vy*Bz - Vz*By) |
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| 83 | dydx[4] = cof*(y[5]*B[0] - y[3]*B[2]) ; // Ay = a*(Vz*Bx - Vx*Bz) |
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| 84 | dydx[5] = cof*(y[3]*B[1] - y[4]*B[0]) ; // Az = a*(Vx*By - Vy*Bx) |
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| 85 | |
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| 86 | G4ThreeVector u(y[3], y[4], y[5]); |
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| 87 | u *= inv_momentum_magnitude; |
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| 88 | |
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| 89 | G4ThreeVector BField(B[0],B[1],B[2]); |
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| 90 | |
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| 91 | G4double udb = anomaly*beta*gamma/(1.+gamma) * (BField * u); |
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| 92 | G4double ucb = (anomaly+1./gamma)/beta; |
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| 93 | |
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| 94 | // Initialise the values of dydx that we do not update. |
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| 95 | dydx[6] = dydx[7] = dydx[8] = 0.0; |
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| 96 | |
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| 97 | G4ThreeVector Spin(y[9],y[10],y[11]); |
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| 98 | G4ThreeVector dSpin; |
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| 99 | |
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| 100 | dSpin = ParticleCharge*omegac*(ucb*(Spin.cross(BField))-udb*(Spin.cross(u))); |
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| 101 | |
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| 102 | dydx[ 9] = dSpin.x(); |
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| 103 | dydx[10] = dSpin.y(); |
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| 104 | dydx[11] = dSpin.z(); |
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| 105 | |
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| 106 | return ; |
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| 107 | } |
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