include/Geant4/G4ExactHelixStepper.hh

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0025 //
0026 // G4ExactHelixStepper
0027 //
0028 // Class description:
0029 //
0030 // Concrete class for particle motion in constant magnetic field.
0031 // Helix a-la-Explicity Euler: x_1 = x_0 + helix(h)
0032 // with helix(h) being a helix piece of length h.
0033 // simplest approach for solving linear differential equations.
0034 // Take the current derivative and add it to the current position.
0035 //
0036 // As the field is assumed constant, an error is not calculated.
0037
0038 // Author: J.Apostolakis, 28.01.2005.
0039 //         Implementation adapted from ExplicitEuler by W.Wander
0040 // --------------------------------------------------------------------
0041 #ifndef G4EXACTHELIXSTEPPER_HH
0042 #define G4EXACTHELIXSTEPPER_HH
0043
0044 #include "G4Types.hh"
0045 #include "G4ThreeVector.hh"
0046
0047 #include "G4MagIntegratorStepper.hh"
0048 #include "G4MagHelicalStepper.hh"
0049 #include "G4Mag_EqRhs.hh"
0050
0051 class G4ExactHelixStepper : public G4MagHelicalStepper
0052 {
0053   public:
0054
0055     G4ExactHelixStepper(G4Mag_EqRhs* EqRhs);
0056    ~G4ExactHelixStepper() override;
0057
0058     G4ExactHelixStepper(const G4ExactHelixStepper&) = delete;
0059     G4ExactHelixStepper& operator=(const G4ExactHelixStepper&) = delete;
0060
0061     void Stepper( const G4double y[],
0062                   const G4double dydx[],
0063                         G4double h,
0064                         G4double yout[],
0065                         G4double yerr[]  ) override;
0066       // Step 'integration' for step size 'h'
0067       // Provides helix starting at y[0 to 6]
0068       // Outputs yout[] and ZERO estimated error yerr[]=0.
0069
0070     void DumbStepper( const G4double y[],
0071                             G4ThreeVector Bfld,
0072                             G4double h,
0073                             G4double yout[] ) override;
0074       // Performs a 'dump' Step without error calculation.
0075
0076     G4double DistChord() const override;
0077       // Estimate maximum distance of curved solution and chord ...
0078
0079     G4int IntegratorOrder() const override;
0080
0081   private:
0082
0083     G4ThreeVector fBfieldValue;
0084       // Initial value of field at last step
0085 };
0086
0087 #endif