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25 // 25 //
26 // G4ExactHelixStepper implementation <<
27 // 26 //
28 // Author: J.Apostolakis, 28.01.2005. << 27 // $Id: G4ExactHelixStepper.cc 66356 2012-12-18 09:02:32Z gcosmo $
29 // Implementation adapted from Explici << 28 //
>> 29 // Helix a-la-Explicity Euler: x_1 = x_0 + helix(h)
>> 30 // with helix(h) being a helix piece of length h
>> 31 // simplest approach for solving linear differential equations.
>> 32 // Take the current derivative and add it to the current position.
>> 33 //
>> 34 // As the field is assumed constant, an error is not calculated.
>> 35 //
>> 36 // Author: J. Apostolakis, 28 Jan 2005
>> 37 // Implementation adapted from ExplicitEuler of W.Wander
30 // ------------------------------------------- 38 // -------------------------------------------------------------------
31 39
32 #include "G4ExactHelixStepper.hh" 40 #include "G4ExactHelixStepper.hh"
33 #include "G4PhysicalConstants.hh" 41 #include "G4PhysicalConstants.hh"
34 #include "G4ThreeVector.hh" 42 #include "G4ThreeVector.hh"
35 #include "G4LineSection.hh" 43 #include "G4LineSection.hh"
36 44
37 G4ExactHelixStepper::G4ExactHelixStepper(G4Mag << 45 G4ExactHelixStepper::G4ExactHelixStepper(G4Mag_EqRhs *EqRhs)
38 : G4MagHelicalStepper(EqRhs), 46 : G4MagHelicalStepper(EqRhs),
39 fBfieldValue(DBL_MAX, DBL_MAX, DBL_MAX) << 47 fBfieldValue(DBL_MAX, DBL_MAX, DBL_MAX),
>> 48 fPtrMagEqOfMot(EqRhs)
40 { 49 {
>> 50 ;
41 } 51 }
42 52
43 G4ExactHelixStepper::~G4ExactHelixStepper() = << 53 G4ExactHelixStepper::~G4ExactHelixStepper() {}
44 <<
45 // ------------------------------------------- <<
46 54
47 void 55 void
48 G4ExactHelixStepper::Stepper( const G4double y 56 G4ExactHelixStepper::Stepper( const G4double yInput[],
49 const G4double*, 57 const G4double*,
50 G4double h 58 G4double hstep,
51 G4double y 59 G4double yOut[],
52 G4double y << 60 G4double yErr[] )
53 { 61 {
54 const G4int nvar = 6; << 62 const G4int nvar = 6;
55 63
56 G4int i; << 64 G4int i;
57 G4ThreeVector Bfld_value; << 65 G4ThreeVector Bfld_value;
58 66
59 MagFieldEvaluate(yInput, Bfld_value); << 67 MagFieldEvaluate(yInput, Bfld_value);
60 AdvanceHelix(yInput, Bfld_value, hstep, yOut << 68 AdvanceHelix(yInput, Bfld_value, hstep, yOut);
61 69
62 // We are assuming a constant field: helix i 70 // We are assuming a constant field: helix is exact
63 // 71 //
64 for(i=0; i<nvar; ++i) << 72 for(i=0;i<nvar;i++)
65 { 73 {
66 yErr[i] = 0.0 ; 74 yErr[i] = 0.0 ;
67 } 75 }
68 76
69 fBfieldValue = Bfld_value; << 77 fBfieldValue=Bfld_value;
70 } 78 }
71 79
72 // ------------------------------------------- <<
73 <<
74 void 80 void
75 G4ExactHelixStepper::DumbStepper( const G4doub << 81 G4ExactHelixStepper::DumbStepper( const G4double yIn[],
76 G4Thre << 82 G4ThreeVector Bfld,
77 G4doub << 83 G4double h,
78 G4doub << 84 G4double yOut[])
79 { 85 {
80 // Assuming a constant field: solution is a 86 // Assuming a constant field: solution is a helix
81 87
82 AdvanceHelix(yIn, Bfld, h, yOut); 88 AdvanceHelix(yIn, Bfld, h, yOut);
83 89
84 G4Exception("G4ExactHelixStepper::DumbSteppe 90 G4Exception("G4ExactHelixStepper::DumbStepper",
85 "GeomField0002", FatalException, 91 "GeomField0002", FatalException,
86 "Should not be called. Stepper m 92 "Should not be called. Stepper must do all the work." );
87 } 93 }
88 94
89 95
90 // ------------------------------------------- 96 // ---------------------------------------------------------------------------
91 97
92 G4double 98 G4double
93 G4ExactHelixStepper::DistChord() const 99 G4ExactHelixStepper::DistChord() const
94 { 100 {
95 // Implementation : must check whether h/R > 101 // Implementation : must check whether h/R > pi !!
96 // If( h/R < pi) DistChord=h/2*std::tan 102 // If( h/R < pi) DistChord=h/2*std::tan(Ang_curve/4)
97 // Else DistChord=R_helix 103 // Else DistChord=R_helix
98 104
99 G4double distChord; 105 G4double distChord;
100 G4double Ang_curve=GetAngCurve(); 106 G4double Ang_curve=GetAngCurve();
101 107
102 if (Ang_curve<=pi) 108 if (Ang_curve<=pi)
103 { 109 {
104 distChord=GetRadHelix()*(1-std::cos(0.5*An 110 distChord=GetRadHelix()*(1-std::cos(0.5*Ang_curve));
105 } 111 }
106 else if(Ang_curve<twopi) 112 else if(Ang_curve<twopi)
107 { 113 {
108 distChord=GetRadHelix()*(1+std::cos(0.5*(t 114 distChord=GetRadHelix()*(1+std::cos(0.5*(twopi-Ang_curve)));
109 } 115 }
110 else 116 else
111 { 117 {
112 distChord=2.*GetRadHelix(); 118 distChord=2.*GetRadHelix();
113 } 119 }
114 120
115 return distChord; 121 return distChord;
116 } 122 }
117 <<
118 // ------------------------------------------- <<
119 123
120 G4int 124 G4int
121 G4ExactHelixStepper::IntegratorOrder() const 125 G4ExactHelixStepper::IntegratorOrder() const
122 { 126 {
123 return 1; 127 return 1;
124 } 128 }
125 129