G4MonopoleEquation.cxx

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// $Id: G4MonopoleEquation.cc 108824 2018-03-09 11:05:41Z gcosmo $
//
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//
//
// class G4MonopoleEquation
//
// Class description:
//
//
//  This is the standard right-hand side for equation of motion.
//
//  The only case another is required is when using a moving reference
//  frame ... or extending the class to include additional Forces,
//  eg an electric field
//
//  10.11.98   V.Grichine
//
//  30.04.10   S.Burdin (modified to use for the monopole trajectories).
//
//  15.06.10   B.Bozsogi (replaced the hardcoded magnetic charge with
//                        the one passed by G4MonopoleTransportation)
//                       +workaround to pass the electric charge.
//
//  12.07.10  S.Burdin (added equations for the electric charges)
// -------------------------------------------------------------------
 
#include "G4MonopoleEquation.hh"
#include "G4PhysicalConstants.hh"
#include "G4SystemOfUnits.hh"
#include "globals.hh"
#include <iomanip>
 
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G4MonopoleEquation::G4MonopoleEquation(G4MagneticField* emField)
  : G4EquationOfMotion(emField)
{
  G4cout << "G4MonopoleEquation::G4MonopoleEquation" << G4endl;
}
 
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G4MonopoleEquation::~G4MonopoleEquation() {}
 
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void G4MonopoleEquation::SetChargeMomentumMass(
  G4ChargeState particleChargeState,
  G4double, // momentum,
  G4double particleMass)
{
  G4double particleMagneticCharge = particleChargeState.MagneticCharge();
  G4double particleElectricCharge = particleChargeState.GetCharge();
 
  //   fElCharge = particleElectricCharge;
  fElCharge = eplus * particleElectricCharge * c_light;
 
  fMagCharge = eplus * particleMagneticCharge * c_light;
 
  // G4cout << " G4MonopoleEquation: ElectricCharge=" << particleElectricCharge
  //           << "; MagneticCharge=" << particleMagneticCharge
  //           << G4endl;
 
  fMassCof = particleMass * particleMass;
}
 
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void G4MonopoleEquation::EvaluateRhsGivenB(
  const G4double y[], const G4double Field[], G4double dydx[]) const
{
  // Components of y:
  //    0-2 dr/ds,
  //    3-5 dp/ds - momentum derivatives
 
  G4double pSquared = y[3] * y[3] + y[4] * y[4] + y[5] * y[5];
 
  G4double Energy = std::sqrt(pSquared + fMassCof);
 
  G4double pModuleInverse = 1.0 / std::sqrt(pSquared);
 
  G4double inverse_velocity = Energy * pModuleInverse / c_light;
 
  G4double cofEl = fElCharge * pModuleInverse;
  G4double cofMag = fMagCharge * Energy * pModuleInverse;
 
  dydx[0] = y[3] * pModuleInverse;
  dydx[1] = y[4] * pModuleInverse;
  dydx[2] = y[5] * pModuleInverse;
 
  // G4double magCharge = twopi * hbar_Planck / (eplus * mu0);
  // magnetic charge in SI units A*m convention
  //  see http://en.wikipedia.org/wiki/Magnetic_monopole
  //   G4cout  << "Magnetic charge:  " << magCharge << G4endl;
  // dp/ds = dp/dt * dt/ds = dp/dt / v = Force / velocity
  // dydx[3] = fMagCharge * Field[0]  * inverse_velocity  * c_light;
  // multiplied by c_light to convert to MeV/mm
  //     dydx[4] = fMagCharge * Field[1]  * inverse_velocity  * c_light;
  //     dydx[5] = fMagCharge * Field[2]  * inverse_velocity  * c_light;
 
  dydx[3] = cofMag * Field[0] + cofEl * (y[4] * Field[2] - y[5] * Field[1]);
  dydx[4] = cofMag * Field[1] + cofEl * (y[5] * Field[0] - y[3] * Field[2]);
  dydx[5] = cofMag * Field[2] + cofEl * (y[3] * Field[1] - y[4] * Field[0]);
 
  //        G4cout << std::setprecision(5)<< "E=" << Energy
  //               << "; p="<< 1/pModuleInverse
  //               << "; mC="<< magCharge
  //               <<"; x=" << y[0]
  //               <<"; y=" << y[1]
  //               <<"; z=" << y[2]
  //               <<"; dydx[3]=" << dydx[3]
  //               <<"; dydx[4]=" << dydx[4]
  //               <<"; dydx[5]=" << dydx[5]
  //               << G4endl;
 
  dydx[6] = 0.; // not used
 
  // Lab Time of flight
  dydx[7] = inverse_velocity;
  return;
}
 
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