G4EqEMFieldWithSpin Class Reference

G4EqEMFieldWithSpin implements the right-hand side of equation of motion in a combined electric and magnetic field. More...

#include <G4EqEMFieldWithSpin.hh>

Inheritance diagram for G4EqEMFieldWithSpin:

Public Member Functions
	G4EqEMFieldWithSpin (G4ElectroMagneticField *emField)
	~G4EqEMFieldWithSpin () 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
G4EquationType	GetEquationType () const override
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
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

G4EqEMFieldWithSpin implements the right-hand side of equation of motion in a combined electric and magnetic field.

Definition at line 48 of file G4EqEMFieldWithSpin.hh.

Constructor & Destructor Documentation

G4EqEMFieldWithSpin()

G4EqEMFieldWithSpin::G4EqEMFieldWithSpin

(

G4ElectroMagneticField *

emField

)

Constructor for G4EqEMFieldWithSpin.

Parameters

[in]

emField

Pointer to the electromagnetic field.

Definition at line 38 of file G4EqEMFieldWithSpin.cc.

  : G4EquationOfMotion( emField ) 
{
}

~G4EqEMFieldWithSpin()

G4EqEMFieldWithSpin::~G4EqEMFieldWithSpin ( )

overridedefault

Default Destructor.

Member Function Documentation

EvaluateRhsGivenB()

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

override

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

Parameters

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

Definition at line 78 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;
}

GetAnomaly()

G4double G4EqEMFieldWithSpin::GetAnomaly ( ) const

inline

Definition at line 89 of file G4EqEMFieldWithSpin.hh.

{ return anomaly; }

GetEquationType()

G4EquationType G4EqEMFieldWithSpin::GetEquationType ( ) const

inlineoverridevirtual

Returns the equation type-ID, "kEqEMfieldWithSpin".

Reimplemented from G4EquationOfMotion.

Definition at line 94 of file G4EqEMFieldWithSpin.hh.

{ return kEqEMfieldWithSpin; }

SetAnomaly()

void G4EqEMFieldWithSpin::SetAnomaly ( G4double a )

inline

Setter and getter for magnetic anomaly.

Definition at line 88 of file G4EqEMFieldWithSpin.hh.

{ anomaly = a; }

SetChargeMomentumMass()

void G4EqEMFieldWithSpin::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 44 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;
}

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

• G4EqEMFieldWithSpin.hh
• G4EqEMFieldWithSpin.cc