include/Geant4/G4BorisScheme.hh

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0024 //
0025 // G4BorisScheme
0026 //
0027 // Class description:
0028 //
0029 // Implementation of the Boris algorithm for advancing
0030 // charged particles in an electromagnetic field.
0031
0032 // Author: Divyansh Tiwari, Google Summer of Code 2022
0033 // Supervision: John Apostolakis,Renee Fatemi, Soon Yung Jun
0034 // --------------------------------------------------------------------
0035 #ifndef G4BORIS_SCHEME_HH
0036 #define G4BORIS_SCHEME_HH
0037
0038 class G4EquationOfMotion;
0039
0040 #include "G4Types.hh"
0041
0042
0043 // class G4EqMagElectricField;
0044
0045 // #include "G4FieldTrack.hh"
0046
0047 #include <CLHEP/Units/PhysicalConstants.h>
0048
0049 class G4BorisScheme
0050 {
0051   public:
0052
0053     G4BorisScheme() = default;
0054     G4BorisScheme( // G4EqMagElectricField
0055        G4EquationOfMotion* equation,
0056                         G4int nvar = 6);
0057    ~G4BorisScheme() = default;
0058
0059     void DoStep( G4double restMass, G4double charge, const G4double yIn[],
0060                  G4double yOut[], G4double hstep) const;
0061
0062   protected:
0063     // Used to implement the 'DoStep' method above
0064     void UpdatePosition(const G4double restMass, const G4double charge, const G4double yIn[],
0065                  G4double yOut[], G4double hstep) const;
0066
0067     void UpdateVelocity(const G4double restMass, const G4double charge, const G4double yIn[],
0068                  G4double yOut[], G4double hstep) const;
0069
0070   public:
0071     // - Methods using the Boris Scheme Stepping to estimate integration error
0072     void StepWithErrorEstimate(const G4double yIn[], G4double restMass, G4double charge, G4double hstep,
0073                                G4double yOut[], G4double yErr[]) const;
0074       // Use two half-steps (comparing to a full step) to obtain output and error estimate
0075
0076    void StepWithMidAndErrorEstimate(const G4double yIn[], G4double restMass, G4double charge, G4double hstep,
0077                                G4double yMid[], G4double yOut[], G4double yErr[]) const;
0078       // Same, and also return mid-point evaluation
0079
0080     // Auxiliary method
0081     inline G4EquationOfMotion* GetEquationOfMotion();
0082     // inline void SetEquationOfMotion(G4EquationOfMotion* equation);  // Un-needed, dangerous
0083
0084     inline G4int GetNumberOfVariables() const;
0085
0086   private:
0087
0088     void copy(G4double dst[], const G4double src[]) const;
0089
0090   private:
0091
0092     G4EquationOfMotion* fEquation = nullptr;
0093     G4int fnvar = 8;
0094     static constexpr G4double c_l = CLHEP::c_light/CLHEP::m*CLHEP::second;
0095 };
0096
0097 #include "G4BorisScheme.icc"
0098 #endif