G4EqMagElectricField.cc

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00027 // $Id: G4EqMagElectricField.cc 69786 2013-05-15 09:38:51Z gcosmo $
00028 //
00029 //
00030 //  This is the standard right-hand side for equation of motion.
00031 //
00032 //  The only case another is required is when using a moving reference
00033 //  frame ... or extending the class to include additional Forces,
00034 //  eg an electric field
00035 //
00036 //  10.11.98   V.Grichine
00037 //
00038 // -------------------------------------------------------------------
00039 
00040 #include "G4EqMagElectricField.hh"
00041 #include "globals.hh"
00042 #include "G4PhysicalConstants.hh"
00043 #include "G4SystemOfUnits.hh"
00044 
00045 void  
00046 G4EqMagElectricField::SetChargeMomentumMass(G4double particleCharge, // e+ units
00047                                             G4double,
00048                                             G4double particleMass)
00049 {
00050    fElectroMagCof =  eplus*particleCharge*c_light ;
00051    fMassCof = particleMass*particleMass ; 
00052 }
00053 
00054 
00055 
00056 void
00057 G4EqMagElectricField::EvaluateRhsGivenB(const G4double y[],
00058                                         const G4double Field[],
00059                                               G4double dydx[] ) const
00060 {
00061 
00062    // Components of y:
00063    //    0-2 dr/ds, 
00064    //    3-5 dp/ds - momentum derivatives 
00065 
00066    G4double pSquared = y[3]*y[3] + y[4]*y[4] + y[5]*y[5] ;
00067 
00068    G4double Energy   = std::sqrt( pSquared + fMassCof );
00069    G4double cof2     = Energy/c_light ;
00070 
00071    G4double pModuleInverse  = 1.0/std::sqrt(pSquared) ;
00072 
00073    //  G4double inverse_velocity = Energy * c_light * pModuleInverse;
00074    G4double inverse_velocity = Energy * pModuleInverse / c_light;
00075 
00076    G4double cof1     = fElectroMagCof*pModuleInverse ;
00077 
00078    //  G4double vDotE = y[3]*Field[3] + y[4]*Field[4] + y[5]*Field[5] ;
00079 
00080 
00081    dydx[0] = y[3]*pModuleInverse ;                         
00082    dydx[1] = y[4]*pModuleInverse ;                         
00083    dydx[2] = y[5]*pModuleInverse ;                        
00084 
00085    dydx[3] = cof1*(cof2*Field[3] + (y[4]*Field[2] - y[5]*Field[1])) ;
00086    
00087    dydx[4] = cof1*(cof2*Field[4] + (y[5]*Field[0] - y[3]*Field[2])) ; 
00088  
00089    dydx[5] = cof1*(cof2*Field[5] + (y[3]*Field[1] - y[4]*Field[0])) ;  
00090 
00091    dydx[6] = 0.;//not used
00092 
00093    // Lab Time of flight
00094    dydx[7] = inverse_velocity;
00095    return ;
00096 }

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