| 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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| 27 | // $Id: G4ExactHelixStepper.cc,v 1.9 2008/10/29 14:34:35 gcosmo Exp $
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| 28 | // GEANT4 tag $Name: $
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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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