1 | // |
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2 | // ******************************************************************** |
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3 | // * License and Disclaimer * |
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4 | // * * |
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9 | // * include a list of copyright holders. * |
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10 | // * * |
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11 | // * Neither the authors of this software system, nor their employing * |
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12 | // * institutes,nor the agencies providing financial support for this * |
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13 | // * work make any representation or warranty, express or implied, * |
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14 | // * regarding this software system or assume any liability for its * |
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15 | // * use. Please see the license in the file LICENSE and URL above * |
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17 | // * * |
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18 | // * This code implementation is the result of the scientific and * |
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19 | // * technical work of the GEANT4 collaboration. * |
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20 | // * By using, copying, modifying or distributing the software (or * |
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21 | // * any work based on the software) you agree to acknowledge its * |
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22 | // * use in resulting scientific publications, and indicate your * |
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23 | // * acceptance of all terms of the Geant4 Software license. * |
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24 | // ******************************************************************** |
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25 | // |
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26 | // |
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27 | // $Id: G4ExactHelixStepper.cc,v 1.9 2008/10/29 14:34:35 gcosmo Exp $ |
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28 | // GEANT4 tag $Name: geant4-09-02-cand-01 $ |
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29 | // |
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30 | // Helix a-la-Explicity Euler: x_1 = x_0 + helix(h) |
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31 | // with helix(h) being a helix piece of length h |
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32 | // simplest approach for solving linear differential equations. |
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33 | // Take the current derivative and add it to the current position. |
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34 | // |
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35 | // As the field is assumed constant, an error is not calculated. |
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36 | // |
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37 | // Author: J. Apostolakis, 28 Jan 2005 |
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38 | // Implementation adapted from ExplicitEuler of W.Wander |
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39 | // ------------------------------------------------------------------- |
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40 | |
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41 | #include "G4ExactHelixStepper.hh" |
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42 | #include "G4ThreeVector.hh" |
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43 | #include "G4LineSection.hh" |
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44 | |
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45 | |
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46 | G4ExactHelixStepper::G4ExactHelixStepper(G4Mag_EqRhs *EqRhs) |
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47 | : G4MagHelicalStepper(EqRhs), |
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48 | fBfieldValue(DBL_MAX, DBL_MAX, DBL_MAX), yInitialEHS(DBL_MAX), yFinalEHS(-DBL_MAX) |
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49 | |
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50 | { |
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51 | const G4int nvar = 6 ; |
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52 | G4int i; |
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53 | for(i=0;i<nvar;i++) { |
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54 | fYInSav[i]= DBL_MAX; |
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55 | } |
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56 | fPtrMagEqOfMot=EqRhs; |
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57 | } |
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58 | |
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59 | G4ExactHelixStepper::~G4ExactHelixStepper() {} |
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60 | |
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61 | void |
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62 | G4ExactHelixStepper::Stepper( const G4double yInput[], |
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63 | const G4double*, |
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64 | G4double hstep, |
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65 | G4double yOut[], |
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66 | G4double yErr[] ) |
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67 | { |
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68 | const G4int nvar = 6 ; |
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69 | |
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70 | G4int i; |
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71 | // G4double yTemp[7], yIn[7] ; |
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72 | G4ThreeVector Bfld_value; |
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73 | |
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74 | for(i=0;i<nvar;i++) { |
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75 | // yIn[i]= yInput[i]; |
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76 | fYInSav[i]= yInput[i]; |
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77 | } |
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78 | |
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79 | MagFieldEvaluate(yInput, Bfld_value) ; |
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80 | |
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81 | // DumbStepper(yIn, Bfld_value, hstep, yTemp); |
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82 | AdvanceHelix(yInput, Bfld_value, hstep, yOut); |
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83 | |
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84 | // We are assuming a constant field: helix is exact. |
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85 | for(i=0;i<nvar;i++) { |
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86 | yErr[i] = 0.0 ; |
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87 | } |
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88 | |
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89 | yInitialEHS = G4ThreeVector( yInput[0], yInput[1], yInput[2]); |
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90 | yFinalEHS = G4ThreeVector( yOut[0], yOut[1], yOut[2]); |
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91 | fBfieldValue=Bfld_value; |
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92 | |
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93 | } |
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94 | |
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95 | void |
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96 | G4ExactHelixStepper::DumbStepper( const G4double yIn[], |
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97 | G4ThreeVector Bfld, |
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98 | G4double h, |
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99 | G4double yOut[]) |
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100 | { |
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101 | // Assuming a constant field: solution is a helix |
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102 | AdvanceHelix(yIn, Bfld, h, yOut); |
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103 | |
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104 | G4Exception("G4ExactHelixStepper::DumbStepper should not be called.", |
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105 | "EHS:NoDumbStepper", FatalException, "Stepper must do all the work." ); |
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106 | } |
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107 | |
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108 | |
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109 | // --------------------------------------------------------------------------- |
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110 | |
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111 | G4double G4ExactHelixStepper::DistChord() const |
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112 | { |
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113 | // Implementation : must check whether h/R > pi !! |
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114 | // If( h/R < pi) DistChord=h/2*std::tan(Ang_curve/4) |
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115 | // Else DistChord=R_helix |
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116 | // |
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117 | G4double distChord; |
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118 | G4double Ang_curve=GetAngCurve(); |
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119 | |
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120 | |
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121 | if(Ang_curve<=pi){ |
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122 | distChord=GetRadHelix()*(1-std::cos(0.5*Ang_curve)); |
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123 | } |
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124 | else |
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125 | if(Ang_curve<twopi){ |
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126 | distChord=GetRadHelix()*(1+std::cos(0.5*(twopi-Ang_curve))); |
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127 | } |
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128 | else{ |
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129 | distChord=2.*GetRadHelix(); |
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130 | } |
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131 | |
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132 | |
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133 | |
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134 | return distChord; |
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135 | |
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136 | } |
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137 | |
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138 | G4int |
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139 | G4ExactHelixStepper::IntegratorOrder() const |
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140 | { |
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141 | return 1; |
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142 | } |
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