G4EqMagElectricField.cc

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// $Id: G4EqMagElectricField.cc 69699 2013-05-13 08:50:30Z gcosmo $
//
//
//  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
//
// -------------------------------------------------------------------

#include "G4EqMagElectricField.hh"
#include "globals.hh"
#include "G4PhysicalConstants.hh"
#include "G4SystemOfUnits.hh"

void  
G4EqMagElectricField::SetChargeMomentumMass(G4ChargeState particleCharge,
                                            G4double,
                                            G4double particleMass)
{
   G4double pcharge = particleCharge.GetCharge();
   fElectroMagCof =  eplus*pcharge*c_light ;
   fMassCof = particleMass*particleMass ; 
}



void
G4EqMagElectricField::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 cof2     = Energy/c_light ;

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

   //  G4double inverse_velocity = Energy * c_light * pModuleInverse;
   G4double inverse_velocity = Energy * pModuleInverse / c_light;

   G4double cof1     = fElectroMagCof*pModuleInverse ;

   //  G4double vDotE = y[3]*Field[3] + y[4]*Field[4] + y[5]*Field[5] ;


   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] = 0.;//not used

   // Lab Time of flight
   dydx[7] = inverse_velocity;
   return ;
}