[831] | 1 | // |
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| 2 | // ******************************************************************** |
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| 3 | // * License and Disclaimer * |
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| 4 | // * * |
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| 5 | // * The Geant4 software is copyright of the Copyright Holders of * |
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| 6 | // * the Geant4 Collaboration. It is provided under the terms and * |
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| 7 | // * conditions of the Geant4 Software License, included in the file * |
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| 8 | // * LICENSE and available at http://cern.ch/geant4/license . These * |
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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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| 16 | // * for the full disclaimer and the limitation of liability. * |
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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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[921] | 27 | // $Id: G4ExactHelixStepper.cc,v 1.9 2008/10/29 14:34:35 gcosmo Exp $ |
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[1337] | 28 | // GEANT4 tag $Name: geant4-09-04-beta-01 $ |
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[831] | 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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[921] | 114 | // If( h/R < pi) DistChord=h/2*std::tan(Ang_curve/4) |
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[831] | 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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