G4RepleteEofM Class Reference

G4RepleteEofM is the right-hand side of equation of motion in a combined field, including: magnetic, electric, gravity, and gradient B field, as well as spin tracking. More...

#include <G4RepleteEofM.hh>

Inheritance diagram for G4RepleteEofM:

Public Member Functions
	G4RepleteEofM (G4Field *field, G4int nvar=8)
	~G4RepleteEofM () override=default
void	SetChargeMomentumMass (G4ChargeState particleCharge, G4double MomentumXc, G4double mass) override
void	EvaluateRhsGivenB (const G4double y[], const G4double Field[], G4double dydx[]) const override
void	SetAnomaly (G4double a)
G4double	GetAnomaly () const
void	SetBField ()
void	SetEField ()
void	SetgradB ()
void	SetSpin ()
Public Member Functions inherited from G4EquationOfMotion
	G4EquationOfMotion (G4Field *Field)
virtual	~G4EquationOfMotion ()=default
virtual void	EvaluateRhsGivenB (const G4double y[], const G4double B[3], G4double dydx[]) const =0
virtual G4EquationType	GetEquationType () const
void	RightHandSide (const G4double y[], G4double dydx[]) const
void	EvaluateRhsReturnB (const G4double y[], G4double dydx[], G4double Field[]) const
void	GetFieldValue (const G4double Point[4], G4double Field[]) const
const G4Field *	GetFieldObj () const
G4Field *	GetFieldObj ()
void	SetFieldObj (G4Field *pField)

Detailed Description

G4RepleteEofM is the right-hand side of equation of motion in a combined field, including: magnetic, electric, gravity, and gradient B field, as well as spin tracking.

Definition at line 50 of file G4RepleteEofM.hh.

Constructor & Destructor Documentation

G4RepleteEofM()

G4RepleteEofM::G4RepleteEofM	(	G4Field *	field,
		G4int	nvar = 8 )

Constructor for G4EquationOfMotion.

Parameters

[in]	field	Pointer to the field.
[in]	nvar	The number of integration variables.

Definition at line 40 of file G4RepleteEofM.cc.

          : G4EquationOfMotion( field ), fNvar(nvar)
{
   fGfield = field->IsGravityActive();
}

~G4RepleteEofM()

G4RepleteEofM::~G4RepleteEofM ( )

overridedefault

Default Destructor.

Member Function Documentation

EvaluateRhsGivenB()

void G4RepleteEofM::EvaluateRhsGivenB ( const G4double y[], const G4double Field[], G4double dydx[] ) const

override

Calculates the value of the derivative, given the value of the field.

Parameters

[in]	y	Coefficients array.
[in]	Field	Field value.
[out]	dydx	Derivatives array.

Definition at line 79 of file G4RepleteEofM.cc.

{
 
   // Components of y:
   //    0-2 dr/ds,
   //    3-5 dp/ds - momentum derivatives
   //    9-11 dSpin/ds = (1/beta) dSpin/dt - spin derivatives
   //
   // The BMT equation, following J.D.Jackson, Classical
   // Electrodynamics, Second Edition,
   // dS/dt = (e/mc) S \cross
   //              [ (g/2-1 +1/\gamma) B
   //               -(g/2-1)\gamma/(\gamma+1) (\beta \cdot B)\beta
   //               -(g/2-\gamma/(\gamma+1) \beta \cross E ]
   // where
   // S = \vec{s}, where S^2 = 1
   // B = \vec{B}
   // \beta = \vec{\beta} = \beta \vec{u} with u^2 = 1
   // E = \vec{E}
   //
   // Field[0,1,2] are the magnetic field components
   // Field[3,4,5] are the electric field components
   // Field[6,7,8] are the gravity  field components
   // The Field[] array may trivially be extended to 18 components
   // Field[ 9] == dB_x/dx; Field[10] == dB_y/dx; Field[11] == dB_z/dx
   // Field[12] == dB_x/dy; Field[13] == dB_y/dy; Field[14] == dB_z/dy
   // Field[15] == dB_x/dz; Field[16] == dB_y/dz; Field[17] == dB_z/dz
 
   G4double momentum_mag_square = y[3]*y[3] + y[4]*y[4] + y[5]*y[5];
   G4double inv_momentum_magnitude = 1.0 / std::sqrt( momentum_mag_square );
 
   G4double Energy = std::sqrt(momentum_mag_square + mass*mass);
   G4double inverse_velocity = Energy*inv_momentum_magnitude/c_light;
 
   G4double cof1 = ElectroMagCof*inv_momentum_magnitude;
   G4double cof2 = Energy/c_light;
   G4double cof3 = inv_momentum_magnitude*mass;
 
   dydx[0] = y[3]*inv_momentum_magnitude;       //  (d/ds)x = Vx/V
   dydx[1] = y[4]*inv_momentum_magnitude;       //  (d/ds)y = Vy/V
   dydx[2] = y[5]*inv_momentum_magnitude;       //  (d/ds)z = Vz/V
 
   dydx[3] = 0.;
   dydx[4] = 0.;
   dydx[5] = 0.;
 
   G4double field[18] = {0.,0.,0.,0.,0.,0.,0.,0.,0.,0.,0.,0.,0.,0.,0.,0.,0.,0.};
 
   field[0] = Field[0];
   field[1] = Field[1];
   field[2] = Field[2];
 
   // Force due to B field - Field[0,1,2]
 
   if (fBfield)
   {
      if (charge != 0.)
      {
         dydx[3] += cof1*(y[4]*field[2] - y[5]*field[1]);
         dydx[4] += cof1*(y[5]*field[0] - y[3]*field[2]);
         dydx[5] += cof1*(y[3]*field[1] - y[4]*field[0]);
      }
   }
 
   // add force due to E field - Field[3,4,5]
 
   if (!fBfield)
   {
      field[3] = Field[0];
      field[4] = Field[1];
      field[5] = Field[2];
   }
   else
   {
      field[3] = Field[3];
      field[4] = Field[4];
      field[5] = Field[5];
   }
 
   if (fEfield)
   {
      if (charge != 0.)
      {
         dydx[3] += cof1*cof2*field[3];
         dydx[4] += cof1*cof2*field[4];
         dydx[5] += cof1*cof2*field[5];
      }
   }
 
   // add force due to gravity field - Field[6,7,8]
 
   if (!fBfield && !fEfield)
   {
      field[6] = Field[0];
      field[7] = Field[1];
      field[8] = Field[2];
   }
   else
   {
      field[6] = Field[6];
      field[7] = Field[7];
      field[8] = Field[8];
   }
 
   if (fGfield)
   {
      if (mass > 0.)
      {
         dydx[3] += field[6]*cof2*cof3/c_light;
         dydx[4] += field[7]*cof2*cof3/c_light;
         dydx[5] += field[8]*cof2*cof3/c_light;
      }
   }
 
   // add force
 
   if (!fBfield && !fEfield && !fGfield)
   {
      field[9]  = Field[0];
      field[10] = Field[1];
      field[11] = Field[2];
      field[12] = Field[3];
      field[13] = Field[4];
      field[14] = Field[5];
      field[15] = Field[6];
      field[16] = Field[7];
      field[17] = Field[8];
   }
   else
   {
      field[9]  = Field[9];
      field[10] = Field[10];
      field[11] = Field[11];
      field[12] = Field[12];
      field[13] = Field[13];
      field[14] = Field[14];
      field[15] = Field[15];
      field[16] = Field[16];
      field[17] = Field[17];
   }
 
   if (fgradB)
   {
      if (magMoment != 0.)
      {
         dydx[3] += magMoment*(y[9]*field[ 9]+y[10]*field[10]+y[11]*field[11])
                                                *inv_momentum_magnitude*Energy;
         dydx[4] += magMoment*(y[9]*field[12]+y[10]*field[13]+y[11]*field[14])
                                                *inv_momentum_magnitude*Energy;
         dydx[5] += magMoment*(y[9]*field[15]+y[10]*field[16]+y[11]*field[17])
                                                *inv_momentum_magnitude*Energy;
      }
   }
 
   dydx[6] = 0.; // not used
 
   // Lab Time of flight
   //
   dydx[7] = inverse_velocity;
 
   if (fNvar == 12)
   {
      dydx[ 8] = 0.; //not used
 
      dydx[ 9] = 0.;
      dydx[10] = 0.;
      dydx[11] = 0.;
   }
 
   if (fSpin)
   {
      G4ThreeVector BField(0.,0.,0.);
      if (fBfield)
      {
         G4ThreeVector F(field[0],field[1],field[2]);
         BField = F;
      }
 
      G4ThreeVector EField(0.,0.,0.);
      if (fEfield)
      {
         G4ThreeVector F(field[3],field[4],field[5]);
         EField = F;
      }
 
      EField /= c_light;
 
      G4ThreeVector u(y[3], y[4], y[5]);
      u *= inv_momentum_magnitude;
 
      G4double udb = anomaly*beta*gamma/(1.+gamma) * (BField * u);
      G4double ucb = (anomaly+1./gamma)/beta;
      G4double uce = anomaly + 1./(gamma+1.);
 
      G4ThreeVector Spin(y[9],y[10],y[11]);
 
      G4double pcharge;
      if (charge == 0.)
      {
        pcharge = 1.;
      }
      else
      {
        pcharge = charge;
      }
 
      G4ThreeVector dSpin(0.,0.,0);
      if (Spin.mag2() != 0.)
      {
         if (fBfield)
         {
           dSpin =
             pcharge*omegac*( ucb*(Spin.cross(BField))-udb*(Spin.cross(u)) );
         }
         if (fEfield)
         {
            dSpin -= pcharge*omegac*( uce*(u*(Spin*EField) - EField*(Spin*u)) );
              // from Jackson
              // -uce*Spin.cross(u.cross(EField)) );
              // but this form has one less operation
         }
      }
 
      dydx[ 9] = dSpin.x();
      dydx[10] = dSpin.y();
      dydx[11] = dSpin.z();
   }
 
   return;
}

GetAnomaly()

G4double G4RepleteEofM::GetAnomaly ( ) const

inline

Definition at line 91 of file G4RepleteEofM.hh.

{ return anomaly; }

SetAnomaly()

void G4RepleteEofM::SetAnomaly ( G4double a )

inline

Setter and getter for the magnetic anomaly.

Definition at line 90 of file G4RepleteEofM.hh.

{ anomaly = a; }

SetBField()

void G4RepleteEofM::SetBField ( )

inline

Modifiers.

Definition at line 96 of file G4RepleteEofM.hh.

{ fBfield = true; }

SetChargeMomentumMass()

void G4RepleteEofM::SetChargeMomentumMass ( G4ChargeState particleCharge, G4double MomentumXc, G4double mass )

overridevirtual

Sets the charge, momentum and mass of the current particle. Used to set the equation's coefficients.

Parameters

[in]	particleCharge	Magnetic charge and moments in e+ units.
[in]	MomentumXc	Particle momentum.
[in]	mass	Particle mass.

Implements G4EquationOfMotion.

Definition at line 47 of file G4RepleteEofM.cc.

{
   charge    = particleCharge.GetCharge();
   mass      = particleMass;
   magMoment = particleCharge.GetMagneticDipoleMoment();
   spin      = particleCharge.GetSpin();
 
   ElectroMagCof =  eplus*charge*c_light;
   omegac = (eplus/mass)*c_light;
 
   G4double muB = 0.5*eplus*hbar_Planck/(mass/c_squared);
 
   G4double g_BMT;
   if ( spin != 0. )
   {
     g_BMT = (std::abs(magMoment)/muB)/spin;
   }
   else
   {
     g_BMT = 2.;
   }
 
   anomaly = (g_BMT - 2.)/2.;
 
   G4double E = std::sqrt(sqr(MomentumXc)+sqr(mass));
   beta  = MomentumXc/E;
   gamma = E/mass;
}

SetEField()

void G4RepleteEofM::SetEField ( )

inline

Definition at line 97 of file G4RepleteEofM.hh.

{ fEfield = true; }

SetgradB()

void G4RepleteEofM::SetgradB ( )

inline

Definition at line 98 of file G4RepleteEofM.hh.

{ fgradB  = true; }

SetSpin()

void G4RepleteEofM::SetSpin ( )

inline

Definition at line 99 of file G4RepleteEofM.hh.

{ fSpin   = true; }

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The documentation for this class was generated from the following files:

• G4RepleteEofM.hh
• G4RepleteEofM.cc