G4EqEMFieldWithSpin Class Reference

#include <G4EqEMFieldWithSpin.hh>

Inheritance diagram for G4EqEMFieldWithSpin:

Collaboration diagram for G4EqEMFieldWithSpin:

Public Member Functions
	G4EqEMFieldWithSpin (G4ElectroMagneticField *emField)
	~G4EqEMFieldWithSpin ()
void	SetChargeMomentumMass (G4ChargeState particleCharge, G4double MomentumXc, G4double mass)
void	EvaluateRhsGivenB (const G4double y[], const G4double Field[], G4double dydx[]) const
void	SetAnomaly (G4double a)
G4double	GetAnomaly () const
Public Member Functions inherited from G4EquationOfMotion
	G4EquationOfMotion (G4Field *Field)
virtual	~G4EquationOfMotion ()
virtual void	EvaluateRhsGivenB (const G4double y[], const G4double B[3], G4double dydx[]) const =0
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
void	SetFieldObj (G4Field *pField)

Detailed Description

Definition at line 49 of file G4EqEMFieldWithSpin.hh.

Constructor & Destructor Documentation

G4EqEMFieldWithSpin::G4EqEMFieldWithSpin

(

G4ElectroMagneticField *

emField

)

Definition at line 45 of file G4EqEMFieldWithSpin.cc.

  : G4EquationOfMotion( emField ), charge(0.), mass(0.), magMoment(0.),
    spin(0.), fElectroMagCof(0.), fMassCof(0.), omegac(0.), 
    anomaly(0.0011659208), beta(0.), gamma(0.)
{
}

G4EqEMFieldWithSpin::~G4EqEMFieldWithSpin

(

)

Definition at line 52 of file G4EqEMFieldWithSpin.cc.

{
} 

Member Function Documentation

void G4EqEMFieldWithSpin::EvaluateRhsGivenB	(	const G4double	y[],
		const G4double	Field[],
		G4double	dydx[]
	)		const

Definition at line 85 of file G4EqEMFieldWithSpin.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}

   G4double pSquared = y[3]*y[3] + y[4]*y[4] + y[5]*y[5] ;

   G4double Energy   = std::sqrt( pSquared + fMassCof );
   G4double cof2     = Energy/c_light ;

   G4double pModuleInverse  = 1.0/std::sqrt(pSquared) ;

   G4double inverse_velocity = Energy * pModuleInverse / c_light;

   G4double cof1     = fElectroMagCof*pModuleInverse ;

   dydx[0] = y[3]*pModuleInverse ;                         
   dydx[1] = y[4]*pModuleInverse ;                         
   dydx[2] = y[5]*pModuleInverse ;                        

   dydx[3] = cof1*(cof2*Field[3] + (y[4]*Field[2] - y[5]*Field[1])) ;
   
   dydx[4] = cof1*(cof2*Field[4] + (y[5]*Field[0] - y[3]*Field[2])) ; 
 
   dydx[5] = cof1*(cof2*Field[5] + (y[3]*Field[1] - y[4]*Field[0])) ;  
   
   dydx[6] = dydx[8] = 0.;//not used

   // Lab Time of flight
   dydx[7] = inverse_velocity;
   
   G4ThreeVector BField(Field[0],Field[1],Field[2]);
   G4ThreeVector EField(Field[3],Field[4],Field[5]);

   EField /= c_light;

   G4ThreeVector u(y[3], y[4], y[5]);
   u *= pModuleInverse;

   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.) {
      dSpin =
      pcharge*omegac*( ucb*(Spin.cross(BField))-udb*(Spin.cross(u))
                           // from Jackson
                           // -uce*Spin.cross(u.cross(EField)) );
                           // but this form has one less operation
                     - uce*(u*(Spin*EField) - EField*(Spin*u)) );
   }

   dydx[ 9] = dSpin.x();
   dydx[10] = dSpin.y();
   dydx[11] = dSpin.z();

   return ;
}

Here is the call graph for this function:

G4double G4EqEMFieldWithSpin::GetAnomaly ( ) const

inline

Definition at line 68 of file G4EqEMFieldWithSpin.hh.

{ return anomaly; }

void G4EqEMFieldWithSpin::SetAnomaly ( G4double  a )

inline

Definition at line 67 of file G4EqEMFieldWithSpin.hh.

{ anomaly = a; }

void G4EqEMFieldWithSpin::SetChargeMomentumMass ( G4ChargeState  particleCharge, G4double  MomentumXc, G4double  mass  )

virtual

Implements G4EquationOfMotion.

Definition at line 57 of file G4EqEMFieldWithSpin.cc.

{
   charge    = particleCharge.GetCharge();
   mass      = particleMass;
   magMoment = particleCharge.GetMagneticDipoleMoment();
   spin      = particleCharge.GetSpin();

   fElectroMagCof =  eplus*charge*c_light ;
   fMassCof = mass*mass;

   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;
}

Here is the call graph for this function:

---

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

• geant4.10.03.p01/source/geometry/magneticfield/include/G4EqEMFieldWithSpin.hh
• geant4.10.03.p01/source/geometry/magneticfield/src/G4EqEMFieldWithSpin.cc