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2 | // ******************************************************************** |
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3 | // * License and Disclaimer * |
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24 | // ******************************************************************** |
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25 | // |
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26 | // |
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27 | // $Id: G4EqMagElectricField.cc,v 1.14 2008/04/24 12:33:35 tnikitin Exp $ |
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28 | // GEANT4 tag $Name: HEAD $ |
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29 | // |
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30 | // |
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31 | // This is the standard right-hand side for equation of motion. |
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32 | // |
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33 | // The only case another is required is when using a moving reference |
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34 | // frame ... or extending the class to include additional Forces, |
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35 | // eg an electric field |
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36 | // |
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37 | // 10.11.98 V.Grichine |
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38 | // |
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39 | // ------------------------------------------------------------------- |
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40 | |
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41 | #include "G4EqMagElectricField.hh" |
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42 | #include "globals.hh" |
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43 | |
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44 | void |
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45 | G4EqMagElectricField::SetChargeMomentumMass(G4double particleCharge, // e+ units |
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46 | G4double, |
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47 | G4double particleMass) |
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48 | { |
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49 | fElectroMagCof = eplus*particleCharge*c_light ; |
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50 | fMassCof = particleMass*particleMass ; |
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51 | } |
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52 | |
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53 | |
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54 | |
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55 | void |
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56 | G4EqMagElectricField::EvaluateRhsGivenB(const G4double y[], |
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57 | const G4double Field[], |
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58 | G4double dydx[] ) const |
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59 | { |
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60 | |
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61 | // Components of y: |
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62 | // 0-2 dr/ds, |
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63 | // 3-5 dp/ds - momentum derivatives |
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64 | |
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65 | G4double pSquared = y[3]*y[3] + y[4]*y[4] + y[5]*y[5] ; |
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66 | |
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67 | G4double Energy = std::sqrt( pSquared + fMassCof ); |
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68 | G4double cof2 = Energy/c_light ; |
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69 | |
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70 | G4double pModuleInverse = 1.0/std::sqrt(pSquared) ; |
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71 | |
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72 | // G4double inverse_velocity = Energy * c_light * pModuleInverse; |
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73 | G4double inverse_velocity = Energy * pModuleInverse / c_light; |
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74 | |
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75 | G4double cof1 = fElectroMagCof*pModuleInverse ; |
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76 | |
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77 | // G4double vDotE = y[3]*Field[3] + y[4]*Field[4] + y[5]*Field[5] ; |
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78 | |
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79 | |
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80 | dydx[0] = y[3]*pModuleInverse ; |
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81 | dydx[1] = y[4]*pModuleInverse ; |
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82 | dydx[2] = y[5]*pModuleInverse ; |
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83 | |
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84 | dydx[3] = cof1*(cof2*Field[3] + (y[4]*Field[2] - y[5]*Field[1])) ; |
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85 | |
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86 | dydx[4] = cof1*(cof2*Field[4] + (y[5]*Field[0] - y[3]*Field[2])) ; |
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87 | |
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88 | dydx[5] = cof1*(cof2*Field[5] + (y[3]*Field[1] - y[4]*Field[0])) ; |
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89 | |
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90 | dydx[6] = 0.;//not used |
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91 | |
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92 | // Lab Time of flight |
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93 | dydx[7] = inverse_velocity; |
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94 | return ; |
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95 | } |
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