| 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: G4HelixExplicitEuler.cc,v 1.8 2007/12/10 16:29:49 gunter Exp $
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| 28 | // GEANT4 tag $Name: geant4-09-04-beta-01 $
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| 29 | //
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| 30 | //
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| 31 | // Helix Explicit Euler: x_1 = x_0 + helix(h)
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| 32 | // with helix(h) being a helix piece of length h
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| 33 | // most simple approach for solving linear differential equations.
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| 34 | // Take the current derivative and add it to the current position.
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| 35 | //
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| 36 | // W.Wander <wwc@mit.edu> 12/09/97
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| 37 | // -------------------------------------------------------------------
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| 38 |
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| 39 | #include "G4HelixExplicitEuler.hh"
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| 40 | #include "G4ThreeVector.hh"
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| 41 |
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| 42 |
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| 43 | void G4HelixExplicitEuler::Stepper( const G4double yInput[7],
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| 44 | const G4double*,
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| 45 | G4double Step,
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| 46 | G4double yOut[7],
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| 47 | G4double yErr[])
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| 48 |
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| 49 | {
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| 50 |
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| 51 | //Estimation of the Stepping Angle
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| 52 |
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| 53 | G4ThreeVector Bfld;
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| 54 | MagFieldEvaluate(yInput, Bfld);
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| 55 |
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| 56 | const G4int nvar = 6 ;
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| 57 | G4int i;
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| 58 | G4double yTemp[7], yIn[7] ;
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| 59 | G4ThreeVector Bfld_midpoint;
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| 60 | // Saving yInput because yInput and yOut can be aliases for same array
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| 61 | for(i=0;i<nvar;i++) yIn[i]=yInput[i];
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| 62 |
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| 63 | G4double h = Step * 0.5;
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| 64 |
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| 65 | // Do full step and two half steps
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| 66 | G4double yTemp2[7];
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| 67 | AdvanceHelix(yIn, Bfld, h, yTemp2,yTemp);
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| 68 | MagFieldEvaluate(yTemp2, Bfld_midpoint) ;
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| 69 | AdvanceHelix(yTemp2, Bfld_midpoint, h, yOut);
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| 70 |
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| 71 | // Error estimation
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| 72 | for(i=0;i<nvar;i++) {
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| 73 | yErr[i] = yOut[i] - yTemp[i] ;
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| 74 | }
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| 75 |
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| 76 | }
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| 77 |
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| 78 | G4double G4HelixExplicitEuler::DistChord() const
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| 79 | {
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| 80 | // Implementation : must check whether h/R > 2 pi !!
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| 81 | // If( h/R < pi) use G4LineSection::DistLine
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| 82 | // Else DistChord=R_helix
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| 83 | //
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| 84 | G4double distChord;
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| 85 | G4double Ang_curve=GetAngCurve();
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| 86 |
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| 87 |
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| 88 | if(Ang_curve<=pi){
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| 89 | distChord=GetRadHelix()*(1-std::cos(0.5*Ang_curve));
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| 90 | }
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| 91 | else
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| 92 | if(Ang_curve<twopi){
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| 93 | distChord=GetRadHelix()*(1+std::cos(0.5*(twopi-Ang_curve)));
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| 94 | }
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| 95 | else{
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| 96 | distChord=2.*GetRadHelix();
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| 97 | }
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| 98 |
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| 99 | return distChord;
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| 100 |
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| 101 | }
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| 102 | void
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| 103 | G4HelixExplicitEuler::DumbStepper( const G4double yIn[],
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| 104 | G4ThreeVector Bfld,
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| 105 | G4double h,
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| 106 | G4double yOut[])
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| 107 | {
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| 108 |
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| 109 | AdvanceHelix(yIn, Bfld, h, yOut);
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| 110 |
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| 111 | }
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