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25 // 25 //
26 // G4HelixExplicitEuler implementation 26 // G4HelixExplicitEuler implementation
27 // 27 //
28 // Helix Explicit Euler: x_1 = x_0 + helix(h) 28 // Helix Explicit Euler: x_1 = x_0 + helix(h)
29 // with helix(h) being a helix piece of lengt 29 // with helix(h) being a helix piece of length h.
30 // Most simple approach for solving linear di 30 // Most simple approach for solving linear differential equations.
31 // Take the current derivative and add it to 31 // Take the current derivative and add it to the current position.
32 // 32 //
33 // Author: W.Wander <wwc@mit.edu>, 12.09.1997 33 // Author: W.Wander <wwc@mit.edu>, 12.09.1997
34 // ------------------------------------------- 34 // -------------------------------------------------------------------
35 35
36 #include "G4HelixExplicitEuler.hh" 36 #include "G4HelixExplicitEuler.hh"
37 #include "G4PhysicalConstants.hh" 37 #include "G4PhysicalConstants.hh"
38 #include "G4ThreeVector.hh" 38 #include "G4ThreeVector.hh"
39 39
40 G4HelixExplicitEuler::G4HelixExplicitEuler(G4M 40 G4HelixExplicitEuler::G4HelixExplicitEuler(G4Mag_EqRhs* EqRhs)
41 : G4MagHelicalStepper(EqRhs) 41 : G4MagHelicalStepper(EqRhs)
42 { 42 {
43 } 43 }
44 44
45 G4HelixExplicitEuler::~G4HelixExplicitEuler() << 45 G4HelixExplicitEuler::~G4HelixExplicitEuler()
>> 46 {
>> 47 }
46 48
47 void G4HelixExplicitEuler::Stepper( const G4do 49 void G4HelixExplicitEuler::Stepper( const G4double yInput[], // [7]
48 const G4do 50 const G4double*,
49 G4do 51 G4double Step,
50 G4do 52 G4double yOut[], // [7]
51 G4do 53 G4double yErr[] )
52 { 54 {
53 // Estimation of the Stepping Angle 55 // Estimation of the Stepping Angle
54 // 56 //
55 G4ThreeVector Bfld; 57 G4ThreeVector Bfld;
56 MagFieldEvaluate(yInput, Bfld); 58 MagFieldEvaluate(yInput, Bfld);
57 59
58 const G4int nvar = 6 ; 60 const G4int nvar = 6 ;
59 G4double yTemp[8], yIn[8] ; 61 G4double yTemp[8], yIn[8] ;
60 G4ThreeVector Bfld_midpoint; 62 G4ThreeVector Bfld_midpoint;
61 63
62 // Saving yInput because yInput and yOut can 64 // Saving yInput because yInput and yOut can be aliases for same array
63 // 65 //
64 for(G4int i=0; i<nvar; ++i) 66 for(G4int i=0; i<nvar; ++i)
65 { 67 {
66 yIn[i] = yInput[i]; 68 yIn[i] = yInput[i];
67 } 69 }
68 70
69 G4double h = Step * 0.5; 71 G4double h = Step * 0.5;
70 72
71 // Do full step and two half steps 73 // Do full step and two half steps
72 // 74 //
73 G4double yTemp2[7]; 75 G4double yTemp2[7];
74 AdvanceHelix(yIn, Bfld, h, yTemp2,yTemp); 76 AdvanceHelix(yIn, Bfld, h, yTemp2,yTemp);
75 MagFieldEvaluate(yTemp2, Bfld_midpoint) ; 77 MagFieldEvaluate(yTemp2, Bfld_midpoint) ;
76 AdvanceHelix(yTemp2, Bfld_midpoint, h, yOut) 78 AdvanceHelix(yTemp2, Bfld_midpoint, h, yOut);
77 SetAngCurve(GetAngCurve() * 2); 79 SetAngCurve(GetAngCurve() * 2);
78 80
79 // Error estimation 81 // Error estimation
80 // 82 //
81 for(G4int i=0; i<nvar; ++i) 83 for(G4int i=0; i<nvar; ++i)
82 { 84 {
83 yErr[i] = yOut[i] - yTemp[i]; 85 yErr[i] = yOut[i] - yTemp[i];
84 } 86 }
85 } 87 }
86 88
87 G4double G4HelixExplicitEuler::DistChord() c 89 G4double G4HelixExplicitEuler::DistChord() const
88 { 90 {
89 // Implementation : must check whether h/R > 91 // Implementation : must check whether h/R > 2 pi !!
90 // If( h/R < pi) use G4LineSection::DistL 92 // If( h/R < pi) use G4LineSection::DistLine
91 // Else DistChord=R_helix 93 // Else DistChord=R_helix
92 // 94 //
93 G4double distChord; 95 G4double distChord;
94 G4double Ang_curve=GetAngCurve(); 96 G4double Ang_curve=GetAngCurve();
95 97
96 98
97 if(Ang_curve<=pi) 99 if(Ang_curve<=pi)
98 { 100 {
99 distChord=GetRadHelix()*(1-std::cos(0.5*An 101 distChord=GetRadHelix()*(1-std::cos(0.5*Ang_curve));
100 } 102 }
101 else if(Ang_curve<twopi) 103 else if(Ang_curve<twopi)
102 { 104 {
103 distChord=GetRadHelix()*(1+std::cos(0.5*(t 105 distChord=GetRadHelix()*(1+std::cos(0.5*(twopi-Ang_curve)));
104 } 106 }
105 else 107 else
106 { 108 {
107 distChord=2.*GetRadHelix(); 109 distChord=2.*GetRadHelix();
108 } 110 }
109 111
110 return distChord; 112 return distChord;
111 } 113 }
112 114
113 void G4HelixExplicitEuler::DumbStepper( const 115 void G4HelixExplicitEuler::DumbStepper( const G4double yIn[],
114 116 G4ThreeVector Bfld,
115 117 G4double h,
116 118 G4double yOut[] )
117 { 119 {
118 AdvanceHelix(yIn, Bfld, h, yOut); 120 AdvanceHelix(yIn, Bfld, h, yOut);
119 } 121 }
120 122