00001 // 00002 // ******************************************************************** 00003 // * License and Disclaimer * 00004 // * * 00005 // * The Geant4 software is copyright of the Copyright Holders of * 00006 // * the Geant4 Collaboration. It is provided under the terms and * 00007 // * conditions of the Geant4 Software License, included in the file * 00008 // * LICENSE and available at http://cern.ch/geant4/license . These * 00009 // * include a list of copyright holders. * 00010 // * * 00011 // * Neither the authors of this software system, nor their employing * 00012 // * institutes,nor the agencies providing financial support for this * 00013 // * work make any representation or warranty, express or implied, * 00014 // * regarding this software system or assume any liability for its * 00015 // * use. Please see the license in the file LICENSE and URL above * 00016 // * for the full disclaimer and the limitation of liability. * 00017 // * * 00018 // * This code implementation is the result of the scientific and * 00019 // * technical work of the GEANT4 collaboration. * 00020 // * By using, copying, modifying or distributing the software (or * 00021 // * any work based on the software) you agree to acknowledge its * 00022 // * use in resulting scientific publications, and indicate your * 00023 // * acceptance of all terms of the Geant4 Software license. * 00024 // ******************************************************************** 00025 // 00026 // 00027 // $Id: G4HelixExplicitEuler.cc 69786 2013-05-15 09:38:51Z gcosmo $ 00028 // 00029 // 00030 // Helix Explicit Euler: x_1 = x_0 + helix(h) 00031 // with helix(h) being a helix piece of length h 00032 // most simple approach for solving linear differential equations. 00033 // Take the current derivative and add it to the current position. 00034 // 00035 // W.Wander <wwc@mit.edu> 12/09/97 00036 // ------------------------------------------------------------------- 00037 00038 #include "G4HelixExplicitEuler.hh" 00039 #include "G4PhysicalConstants.hh" 00040 #include "G4ThreeVector.hh" 00041 00042 00043 void G4HelixExplicitEuler::Stepper( const G4double yInput[7], 00044 const G4double*, 00045 G4double Step, 00046 G4double yOut[7], 00047 G4double yErr[]) 00048 00049 { 00050 00051 //Estimation of the Stepping Angle 00052 00053 G4ThreeVector Bfld; 00054 MagFieldEvaluate(yInput, Bfld); 00055 00056 const G4int nvar = 6 ; 00057 G4int i; 00058 G4double yTemp[7], yIn[7] ; 00059 G4ThreeVector Bfld_midpoint; 00060 // Saving yInput because yInput and yOut can be aliases for same array 00061 for(i=0;i<nvar;i++) yIn[i]=yInput[i]; 00062 00063 G4double h = Step * 0.5; 00064 00065 // Do full step and two half steps 00066 G4double yTemp2[7]; 00067 AdvanceHelix(yIn, Bfld, h, yTemp2,yTemp); 00068 MagFieldEvaluate(yTemp2, Bfld_midpoint) ; 00069 AdvanceHelix(yTemp2, Bfld_midpoint, h, yOut); 00070 00071 // Error estimation 00072 for(i=0;i<nvar;i++) { 00073 yErr[i] = yOut[i] - yTemp[i] ; 00074 } 00075 00076 } 00077 00078 G4double G4HelixExplicitEuler::DistChord() const 00079 { 00080 // Implementation : must check whether h/R > 2 pi !! 00081 // If( h/R < pi) use G4LineSection::DistLine 00082 // Else DistChord=R_helix 00083 // 00084 G4double distChord; 00085 G4double Ang_curve=GetAngCurve(); 00086 00087 00088 if(Ang_curve<=pi){ 00089 distChord=GetRadHelix()*(1-std::cos(0.5*Ang_curve)); 00090 } 00091 else 00092 if(Ang_curve<twopi){ 00093 distChord=GetRadHelix()*(1+std::cos(0.5*(twopi-Ang_curve))); 00094 } 00095 else{ 00096 distChord=2.*GetRadHelix(); 00097 } 00098 00099 return distChord; 00100 00101 } 00102 void 00103 G4HelixExplicitEuler::DumbStepper( const G4double yIn[], 00104 G4ThreeVector Bfld, 00105 G4double h, 00106 G4double yOut[]) 00107 { 00108 00109 AdvanceHelix(yIn, Bfld, h, yOut); 00110 00111 }