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25 // 25 //
26 // G4ExactHelixStepper implementation <<
27 // 26 //
28 // Author: J.Apostolakis, 28.01.2005. << 27 // $Id: G4ExactHelixStepper.cc,v 1.9 2008/10/29 14:34:35 gcosmo Exp $
29 // Implementation adapted from Explici << 28 // GEANT4 tag $Name: geant4-09-02-patch-04 $
>> 29 //
>> 30 // Helix a-la-Explicity Euler: x_1 = x_0 + helix(h)
>> 31 // with helix(h) being a helix piece of length h
>> 32 // simplest approach for solving linear differential equations.
>> 33 // Take the current derivative and add it to the current position.
>> 34 //
>> 35 // As the field is assumed constant, an error is not calculated.
>> 36 //
>> 37 // Author: J. Apostolakis, 28 Jan 2005
>> 38 // Implementation adapted from ExplicitEuler of W.Wander
30 // ------------------------------------------- 39 // -------------------------------------------------------------------
31 40
32 #include "G4ExactHelixStepper.hh" 41 #include "G4ExactHelixStepper.hh"
33 #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
>> 46 G4ExactHelixStepper::G4ExactHelixStepper(G4Mag_EqRhs *EqRhs)
38 : G4MagHelicalStepper(EqRhs), 47 : G4MagHelicalStepper(EqRhs),
39 fBfieldValue(DBL_MAX, DBL_MAX, DBL_MAX) << 48 fBfieldValue(DBL_MAX, DBL_MAX, DBL_MAX), yInitialEHS(DBL_MAX), yFinalEHS(-DBL_MAX)
>> 49
40 { 50 {
>> 51 const G4int nvar = 6 ;
>> 52 G4int i;
>> 53 for(i=0;i<nvar;i++) {
>> 54 fYInSav[i]= DBL_MAX;
>> 55 }
>> 56 fPtrMagEqOfMot=EqRhs;
41 } 57 }
42 58
43 G4ExactHelixStepper::~G4ExactHelixStepper() = << 59 G4ExactHelixStepper::~G4ExactHelixStepper() {}
44 <<
45 // ------------------------------------------- <<
46 60
47 void 61 void
48 G4ExactHelixStepper::Stepper( const G4double y 62 G4ExactHelixStepper::Stepper( const G4double yInput[],
49 const G4double*, << 63 const G4double*,
50 G4double h << 64 G4double hstep,
51 G4double y << 65 G4double yOut[],
52 G4double y << 66 G4double yErr[] )
53 { 67 {
54 const G4int nvar = 6; << 68 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 i <<
63 // <<
64 for(i=0; i<nvar; ++i) <<
65 { <<
66 yErr[i] = 0.0 ; <<
67 } <<
68 69
69 fBfieldValue = Bfld_value; << 70 G4int i;
>> 71 // G4double yTemp[7], yIn[7] ;
>> 72 G4ThreeVector Bfld_value;
>> 73
>> 74 for(i=0;i<nvar;i++) {
>> 75 // yIn[i]= yInput[i];
>> 76 fYInSav[i]= yInput[i];
>> 77 }
>> 78
>> 79 MagFieldEvaluate(yInput, Bfld_value) ;
>> 80
>> 81 // DumbStepper(yIn, Bfld_value, hstep, yTemp);
>> 82 AdvanceHelix(yInput, Bfld_value, hstep, yOut);
>> 83
>> 84 // We are assuming a constant field: helix is exact.
>> 85 for(i=0;i<nvar;i++) {
>> 86 yErr[i] = 0.0 ;
>> 87 }
>> 88
>> 89 yInitialEHS = G4ThreeVector( yInput[0], yInput[1], yInput[2]);
>> 90 yFinalEHS = G4ThreeVector( yOut[0], yOut[1], yOut[2]);
>> 91 fBfieldValue=Bfld_value;
>> 92
70 } 93 }
71 94
72 // ------------------------------------------- <<
73 <<
74 void 95 void
75 G4ExactHelixStepper::DumbStepper( const G4doub << 96 G4ExactHelixStepper::DumbStepper( const G4double yIn[],
76 G4Thre << 97 G4ThreeVector Bfld,
77 G4doub << 98 G4double h,
78 G4doub << 99 G4double yOut[])
79 { 100 {
80 // Assuming a constant field: solution is a 101 // Assuming a constant field: solution is a helix
81 <<
82 AdvanceHelix(yIn, Bfld, h, yOut); 102 AdvanceHelix(yIn, Bfld, h, yOut);
83 103
84 G4Exception("G4ExactHelixStepper::DumbSteppe << 104 G4Exception("G4ExactHelixStepper::DumbStepper should not be called.",
85 "GeomField0002", FatalException, << 105 "EHS:NoDumbStepper", FatalException, "Stepper must do all the work." );
86 "Should not be called. Stepper m <<
87 } 106 }
88 107
89 108
90 // ------------------------------------------- 109 // ---------------------------------------------------------------------------
91 110
92 G4double << 111 G4double G4ExactHelixStepper::DistChord() const
93 G4ExactHelixStepper::DistChord() const <<
94 { 112 {
95 // Implementation : must check whether h/R > 113 // Implementation : must check whether h/R > pi !!
96 // If( h/R < pi) DistChord=h/2*std::tan 114 // If( h/R < pi) DistChord=h/2*std::tan(Ang_curve/4)
97 // Else DistChord=R_helix 115 // Else DistChord=R_helix
98 << 116 //
99 G4double distChord; 117 G4double distChord;
100 G4double Ang_curve=GetAngCurve(); 118 G4double Ang_curve=GetAngCurve();
101 119
102 if (Ang_curve<=pi) << 120
103 { << 121 if(Ang_curve<=pi){
104 distChord=GetRadHelix()*(1-std::cos(0.5*An << 122 distChord=GetRadHelix()*(1-std::cos(0.5*Ang_curve));
105 } << 123 }
106 else if(Ang_curve<twopi) << 124 else
107 { << 125 if(Ang_curve<twopi){
108 distChord=GetRadHelix()*(1+std::cos(0.5*(t << 126 distChord=GetRadHelix()*(1+std::cos(0.5*(twopi-Ang_curve)));
109 } << 127 }
110 else << 128 else{
111 { << 129 distChord=2.*GetRadHelix();
112 distChord=2.*GetRadHelix(); << 130 }
113 } << 131
>> 132
114 133
115 return distChord; 134 return distChord;
>> 135
116 } 136 }
117 <<
118 // ------------------------------------------- <<
119 137
120 G4int 138 G4int
121 G4ExactHelixStepper::IntegratorOrder() const 139 G4ExactHelixStepper::IntegratorOrder() const
122 { 140 {
123 return 1; 141 return 1;
124 } 142 }
125 143