[819] | 1 | // |
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| 2 | // ******************************************************************** |
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| 3 | // * License and Disclaimer * |
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| 6 | // * the Geant4 Collaboration. It is provided under the terms and * |
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| 8 | // * LICENSE and available at http://cern.ch/geant4/license . These * |
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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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| 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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[1196] | 26 | // $Id: G4BohrFluctuations.cc,v 1.8 2009/09/29 11:33:22 vnivanch Exp $ |
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[1228] | 27 | // GEANT4 tag $Name: geant4-09-03 $ |
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[819] | 28 | // |
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| 29 | // ------------------------------------------------------------------- |
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| 30 | // |
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| 31 | // GEANT4 Class file |
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| 32 | // |
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| 33 | // |
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| 34 | // File name: G4BohrFluctuations |
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| 35 | // |
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| 36 | // Author: Vladimir Ivanchenko |
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| 37 | // |
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| 38 | // Creation date: 02.04.2003 |
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| 39 | // |
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| 40 | // Modifications: |
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| 41 | // |
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| 42 | // 23-05-03 Add control on parthalogical cases (V.Ivanchenko) |
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| 43 | // 16-10-03 Changed interface to Initialisation (V.Ivanchenko) |
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| 44 | // |
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| 45 | // Class Description: Sampling of Gaussion fluctuations |
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| 46 | // |
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| 47 | // ------------------------------------------------------------------- |
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| 48 | // |
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| 49 | |
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| 50 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 51 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 52 | |
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| 53 | #include "G4BohrFluctuations.hh" |
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| 54 | #include "Randomize.hh" |
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| 55 | #include "G4Poisson.hh" |
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| 56 | #include "G4ParticleDefinition.hh" |
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| 57 | |
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| 58 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 59 | |
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| 60 | using namespace std; |
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| 61 | |
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| 62 | G4BohrFluctuations::G4BohrFluctuations(const G4String& nam) |
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| 63 | :G4VEmFluctuationModel(nam), |
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| 64 | particle(0), |
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[1196] | 65 | minNumberInteractionsBohr(2.0), |
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[819] | 66 | minFraction(0.2), |
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| 67 | xmin(0.2), |
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| 68 | minLoss(0.001*eV) |
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| 69 | {} |
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| 70 | |
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| 71 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 72 | |
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| 73 | G4BohrFluctuations::~G4BohrFluctuations() |
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| 74 | {} |
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| 75 | |
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| 76 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 77 | |
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| 78 | void G4BohrFluctuations::InitialiseMe(const G4ParticleDefinition* part) |
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| 79 | { |
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| 80 | particle = part; |
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| 81 | particleMass = part->GetPDGMass(); |
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| 82 | G4double q = part->GetPDGCharge()/eplus; |
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| 83 | chargeSquare = q*q; |
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| 84 | } |
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| 85 | |
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| 86 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 87 | |
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| 88 | G4double G4BohrFluctuations::SampleFluctuations(const G4Material* material, |
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| 89 | const G4DynamicParticle* dp, |
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| 90 | G4double& tmax, |
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| 91 | G4double& length, |
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| 92 | G4double& meanLoss) |
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| 93 | { |
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| 94 | if(meanLoss <= minLoss) return meanLoss; |
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| 95 | G4double siga = Dispersion(material,dp,tmax,length); |
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| 96 | G4double loss = meanLoss; |
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| 97 | |
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| 98 | G4double navr = meanLoss*meanLoss/siga; |
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| 99 | //G4cout << "### meanLoss= " << meanLoss << " navr= " << navr << G4endl; |
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| 100 | if (navr >= minNumberInteractionsBohr) { |
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| 101 | |
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| 102 | // Increase fluctuations for big fractional energy loss |
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| 103 | if ( meanLoss > minFraction*kineticEnergy ) { |
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| 104 | G4double gam = (kineticEnergy - meanLoss)/particleMass + 1.0; |
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| 105 | G4double b2 = 1.0 - 1.0/(gam*gam); |
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| 106 | if(b2 < xmin*beta2) b2 = xmin*beta2; |
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| 107 | G4double x = b2/beta2; |
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| 108 | G4double x3 = 1.0/(x*x*x); |
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| 109 | siga *= 0.25*(1.0 + x)*(x3 + (1.0/b2 - 0.5)/(1.0/beta2 - 0.5) ); |
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| 110 | } |
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| 111 | siga = sqrt(siga); |
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| 112 | G4double twomeanLoss = meanLoss + meanLoss; |
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[1196] | 113 | //G4cout << "siga= " << siga << " 2edp= " << twomeanLoss <<G4endl; |
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[819] | 114 | |
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| 115 | if(twomeanLoss < siga) { |
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| 116 | G4double x; |
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| 117 | do { |
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| 118 | loss = twomeanLoss*G4UniformRand(); |
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| 119 | x = (loss - meanLoss)/siga; |
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| 120 | } while (1.0 - 0.5*x*x < G4UniformRand()); |
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| 121 | } else { |
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| 122 | do { |
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| 123 | loss = G4RandGauss::shoot(meanLoss,siga); |
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| 124 | } while (0.0 > loss || loss > twomeanLoss); |
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| 125 | } |
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| 126 | |
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| 127 | // Poisson fluctuations |
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| 128 | } else { |
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| 129 | G4double n = (G4double)(G4Poisson(navr)); |
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| 130 | loss = meanLoss*n/navr; |
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| 131 | } |
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[1196] | 132 | //G4cout << "loss= " << loss << G4endl; |
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[819] | 133 | |
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| 134 | return loss; |
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| 135 | } |
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| 136 | |
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| 137 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 138 | |
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[1055] | 139 | G4double G4BohrFluctuations::Dispersion(const G4Material* material, |
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| 140 | const G4DynamicParticle* dp, |
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| 141 | G4double& tmax, |
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| 142 | G4double& length) |
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| 143 | { |
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| 144 | if(!particle) InitialiseMe(dp->GetDefinition()); |
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[819] | 145 | |
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[1055] | 146 | G4double electronDensity = material->GetElectronDensity(); |
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| 147 | kineticEnergy = dp->GetKineticEnergy(); |
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| 148 | G4double etot = kineticEnergy + particleMass; |
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| 149 | beta2 = kineticEnergy*(kineticEnergy + 2.0*particleMass)/(etot*etot); |
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| 150 | G4double siga = (1.0/beta2 - 0.5) * twopi_mc2_rcl2 * tmax * length |
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| 151 | * electronDensity * chargeSquare; |
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| 152 | |
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| 153 | return siga; |
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| 154 | } |
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| 155 | |
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| 156 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 157 | |
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| 158 | |
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