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25 //
26 // G4ExactHelixStepper implementation
27 //
28 // Author: J.Apostolakis, 28.01.2005.
29 // Implementation adapted from ExplicitEuler by W.Wander
30 // -------------------------------------------------------------------
31
32 #include "G4ExactHelixStepper.hh"
33 #include "G4PhysicalConstants.hh"
34 #include "G4ThreeVector.hh"
35 #include "G4LineSection.hh"
36
37 G4ExactHelixStepper::G4ExactHelixStepper(G4Mag_EqRhs* EqRhs)
38 : G4MagHelicalStepper(EqRhs),
39 fBfieldValue(DBL_MAX, DBL_MAX, DBL_MAX)
40 {
41 }
42
43 G4ExactHelixStepper::~G4ExactHelixStepper() = default;
44
45 // ---------------------------------------------------------------------------
46
47 void
48 G4ExactHelixStepper::Stepper( const G4double yInput[],
49 const G4double*,
50 G4double hstep,
51 G4double yOut[],
52 G4double yErr[] )
53 {
54 const G4int nvar = 6;
55
56 G4int i;
57 G4ThreeVector Bfld_value;
58
59 MagFieldEvaluate(yInput, Bfld_value);
60 AdvanceHelix(yInput, Bfld_value, hstep, yOut);
61
62 // We are assuming a constant field: helix is exact
63 //
64 for(i=0; i<nvar; ++i)
65 {
66 yErr[i] = 0.0 ;
67 }
68
69 fBfieldValue = Bfld_value;
70 }
71
72 // ---------------------------------------------------------------------------
73
74 void
75 G4ExactHelixStepper::DumbStepper( const G4double yIn[],
76 G4ThreeVector Bfld,
77 G4double h,
78 G4double yOut[])
79 {
80 // Assuming a constant field: solution is a helix
81
82 AdvanceHelix(yIn, Bfld, h, yOut);
83
84 G4Exception("G4ExactHelixStepper::DumbStepper",
85 "GeomField0002", FatalException,
86 "Should not be called. Stepper must do all the work." );
87 }
88
89
90 // ---------------------------------------------------------------------------
91
92 G4double
93 G4ExactHelixStepper::DistChord() const
94 {
95 // Implementation : must check whether h/R > pi !!
96 // If( h/R < pi) DistChord=h/2*std::tan(Ang_curve/4)
97 // Else DistChord=R_helix
98
99 G4double distChord;
100 G4double Ang_curve=GetAngCurve();
101
102 if (Ang_curve<=pi)
103 {
104 distChord=GetRadHelix()*(1-std::cos(0.5*Ang_curve));
105 }
106 else if(Ang_curve<twopi)
107 {
108 distChord=GetRadHelix()*(1+std::cos(0.5*(twopi-Ang_curve)));
109 }
110 else
111 {
112 distChord=2.*GetRadHelix();
113 }
114
115 return distChord;
116 }
117
118 // ---------------------------------------------------------------------------
119
120 G4int
121 G4ExactHelixStepper::IntegratorOrder() const
122 {
123 return 1;
124 }
125