Gabriele Cosmo
503 lines
18 KiB
C++
503 lines
18 KiB
C++
// This code implementation is the intellectual property of
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// the GEANT4 collaboration.
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//
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// By copying, distributing or modifying the Program (or any work
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// based on the Program) you indicate your acceptance of this statement,
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// and all its terms.
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//
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// $Id: G4LENeutronInelastic.cc,v 1.2.8.1.2.2 1999/12/10 15:42:13 gunter Exp $
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// GEANT4 tag $Name: geant4-01-01 $
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//
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// Hadronic Process: Low Energy Neutron Inelastic Process
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// J.L. Chuma, TRIUMF, 04-Feb-1997
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#include "G4LENeutronInelastic.hh"
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#include "Randomize.hh"
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#include "G4Electron.hh"
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// #include "DumpFrame.hh"
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G4VParticleChange *
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G4LENeutronInelastic::ApplyYourself( const G4Track &aTrack,
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G4Nucleus &targetNucleus )
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{
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theParticleChange.Initialize( aTrack );
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const G4DynamicParticle *originalIncident = aTrack.GetDynamicParticle();
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//
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// create the target particle
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//
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G4DynamicParticle *originalTarget = targetNucleus.ReturnTargetParticle();
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if( verboseLevel > 1 )
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{
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G4Material *targetMaterial = aTrack.GetMaterial();
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G4cout << "G4LENeutronInelastic::ApplyYourself called" << G4endl;
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G4cout << "kinetic energy = " << originalIncident->GetKineticEnergy()/MeV << "MeV, ";
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G4cout << "target material = " << targetMaterial->GetName() << ", ";
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G4cout << "target particle = " << originalTarget->GetDefinition()->GetParticleName()
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<< G4endl;
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}
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if( originalIncident->GetKineticEnergy()/MeV < 0.000001 )
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G4Exception("G4LENeutronInelastic: should be capture process!");
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if( originalIncident->GetMomentum().mag()/MeV < 0.000001 )
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G4Exception("G4LENeutronInelastic: should be capture process!");
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G4ReactionProduct modifiedOriginal;
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modifiedOriginal = *originalIncident;
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G4ReactionProduct targetParticle;
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targetParticle = *originalTarget;
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if( originalIncident->GetKineticEnergy()/GeV < 0.01 + 2.*G4UniformRand()/9. )
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{
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SlowNeutron( originalIncident, modifiedOriginal, targetParticle, targetNucleus );
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delete originalTarget;
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return &theParticleChange;
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}
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//
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// Fermi motion and evaporation
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// As of Geant3, the Fermi energy calculation had not been Done
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//
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G4double ek = originalIncident->GetKineticEnergy()/MeV;
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G4double amas = originalIncident->GetDefinition()->GetPDGMass()/MeV;
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G4double tkin = targetNucleus.Cinema( ek );
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ek += tkin;
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modifiedOriginal.SetKineticEnergy( ek*MeV );
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G4double et = ek + amas;
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G4double p = sqrt( abs((et-amas)*(et+amas)) );
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G4double pp = modifiedOriginal.GetMomentum().mag()/MeV;
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if( pp > 0.0 )
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{
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G4ThreeVector momentum = modifiedOriginal.GetMomentum();
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modifiedOriginal.SetMomentum( momentum * (p/pp) );
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}
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//
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// calculate black track energies
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//
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tkin = targetNucleus.EvaporationEffects( ek );
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ek -= tkin;
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modifiedOriginal.SetKineticEnergy( ek*MeV );
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et = ek + amas;
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p = sqrt( abs((et-amas)*(et+amas)) );
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pp = modifiedOriginal.GetMomentum().mag()/MeV;
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if( pp > 0.0 )
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{
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G4ThreeVector momentum = modifiedOriginal.GetMomentum();
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modifiedOriginal.SetMomentum( momentum * (p/pp) );
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}
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const G4double cutOff = 0.1;
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if( modifiedOriginal.GetKineticEnergy()/MeV <= cutOff )
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{
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SlowNeutron( originalIncident, modifiedOriginal, targetParticle, targetNucleus );
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delete originalTarget;
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return &theParticleChange;
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}
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G4ReactionProduct currentParticle = modifiedOriginal;
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currentParticle.SetSide( 1 ); // incident always goes in forward hemisphere
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targetParticle.SetSide( -1 ); // target always goes in backward hemisphere
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G4bool incidentHasChanged = false;
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G4bool targetHasChanged = false;
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G4bool quasiElastic = false;
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G4FastVector<G4ReactionProduct,128> vec; // vec will contain the secondary particles
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G4int vecLen = 0;
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vec.Initialize( 0 );
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Cascade( vec, vecLen,
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originalIncident, currentParticle, targetParticle,
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incidentHasChanged, targetHasChanged, quasiElastic );
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CalculateMomenta( vec, vecLen,
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originalIncident, originalTarget, modifiedOriginal,
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targetNucleus, currentParticle, targetParticle,
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incidentHasChanged, targetHasChanged, quasiElastic );
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SetUpChange( vec, vecLen,
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currentParticle, targetParticle,
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incidentHasChanged );
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delete originalTarget;
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return &theParticleChange;
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}
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void
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G4LENeutronInelastic::SlowNeutron(
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const G4DynamicParticle *originalIncident,
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G4ReactionProduct &modifiedOriginal,
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G4ReactionProduct &targetParticle,
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G4Nucleus &targetNucleus )
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{
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G4ParticleDefinition *aProton = G4Proton::Proton();
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G4ParticleDefinition *aNeutron = G4Neutron::Neutron();
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G4ParticleDefinition *aDeuteron = G4Deuteron::Deuteron();
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G4ParticleDefinition *aTriton = G4Triton::Triton();
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G4ParticleDefinition *anAlpha = G4Alpha::Alpha();
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const G4double aProtonMass = aProton->GetPDGMass()/MeV;
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const G4double aNeutronMass = aNeutron->GetPDGMass()/MeV;
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const G4double aDeuteronMass = aDeuteron->GetPDGMass()/MeV;
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const G4double aTritonMass = aTriton->GetPDGMass()/MeV;
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const G4double anAlphaMass = anAlpha->GetPDGMass()/MeV;
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const G4double A = targetNucleus.GetN(); // atomic weight
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const G4double Z = targetNucleus.GetZ(); // atomic number
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G4double currentKinetic = modifiedOriginal.GetKineticEnergy()/MeV;
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G4double currentMass = modifiedOriginal.GetMass()/MeV;
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if( A < 1.5 ) // Hydrogen
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{
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//
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// very simple simulation of scattering angle and energy
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// nonrelativistic approximation with isotropic angular
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// distribution in the cms system
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//
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G4double cost1, eka = 0.0;
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while (eka <= 0.0)
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{
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cost1 = -1.0 + 2.0*G4UniformRand();
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eka = 1.0 + 2.0*cost1*A + A*A;
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}
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G4double cost = G4std::min( 1.0, G4std::max( -1.0, (A*cost1+1.0)/sqrt(eka) ) );
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eka /= (1.0+A)*(1.0+A);
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G4double ek = currentKinetic*MeV/GeV;
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G4double amas = currentMass*MeV/GeV;
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ek *= eka;
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G4double en = ek + amas;
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G4double p = sqrt(abs(en*en-amas*amas));
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G4double sint = sqrt(abs(1.0-cost*cost));
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G4double phi = G4UniformRand()*twopi;
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G4double px = sint*sin(phi);
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G4double py = sint*cos(phi);
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G4double pz = cost;
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targetParticle.SetMomentum( px*GeV, py*GeV, pz*GeV );
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G4double pxO = originalIncident->GetMomentum().x()/GeV;
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G4double pyO = originalIncident->GetMomentum().y()/GeV;
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G4double pzO = originalIncident->GetMomentum().z()/GeV;
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G4double ptO = pxO*pxO + pyO+pyO;
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if( ptO > 0.0 )
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{
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G4double pO = sqrt(pxO*pxO+pyO*pyO+pzO*pzO);
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cost = pzO/pO;
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sint = 0.5*(sqrt(abs((1.0-cost)*(1.0+cost)))+sqrt(ptO)/pO);
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G4double ph = pi/2.0;
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if( pyO < 0.0 )ph = ph*1.5;
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if( abs(pxO) > 0.000001 )ph = atan2(pyO,pxO);
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G4double cosp = cos(ph);
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G4double sinp = sin(ph);
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px = cost*cosp*px - sinp*py+sint*cosp*pz;
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py = cost*sinp*px + cosp*py+sint*sinp*pz;
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pz = -sint*px + cost*pz;
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}
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else
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{
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if( pz < 0.0 )pz *= -1.0;
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}
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G4double pu = sqrt(px*px+py*py+pz*pz);
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modifiedOriginal.SetMomentum( targetParticle.GetMomentum() * (p/pu) );
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modifiedOriginal.SetKineticEnergy( ek*GeV );
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targetParticle.SetMomentum(
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originalIncident->GetMomentum() - modifiedOriginal.GetMomentum() );
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G4double pp = targetParticle.GetMomentum().mag();
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G4double tarmas = targetParticle.GetMass();
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targetParticle.SetTotalEnergy( sqrt( pp*pp + tarmas*tarmas ) );
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theParticleChange.SetEnergyChange( modifiedOriginal.GetKineticEnergy() );
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theParticleChange.SetNumberOfSecondaries( 1 );
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G4DynamicParticle *pd = new G4DynamicParticle;
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pd->SetDefinition( targetParticle.GetDefinition() );
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pd->SetMomentum( targetParticle.GetMomentum() );
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theParticleChange.AddSecondary( pd );
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return;
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}
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G4FastVector<G4ReactionProduct,3> vec; // vec will contain the secondary particles
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G4int vecLen = 0;
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vec.Initialize( 0 );
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G4double theAtomicMass = targetNucleus.AtomicMass( A, Z )-(Z)*G4Electron::Electron()->GetPDGMass();
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G4double massVec[9];
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massVec[0] = targetNucleus.AtomicMass( A+1.0, Z )-(Z)*G4Electron::Electron()->GetPDGMass();
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massVec[1] = theAtomicMass;
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massVec[2] = targetNucleus.AtomicMass( A , Z-1.0 )-(Z-1.0)*G4Electron::Electron()->GetPDGMass();
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massVec[3] = targetNucleus.AtomicMass( A-1.0, Z-1.0 )-(Z-1.0)*G4Electron::Electron()->GetPDGMass();
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massVec[4] = targetNucleus.AtomicMass( A-2.0, Z-1.0 )-(Z-1.0)*G4Electron::Electron()->GetPDGMass();
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massVec[5] = targetNucleus.AtomicMass( A-3.0, Z-2.0 )-(Z-2.0)*G4Electron::Electron()->GetPDGMass();
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massVec[6] = targetNucleus.AtomicMass( A-1.0, Z );
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massVec[7] = massVec[3];
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massVec[8] = targetNucleus.AtomicMass( A-1.0, Z-2.0 )-(Z-2.0)*G4Electron::Electron()->GetPDGMass();
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theReactionDynamics.NuclearReaction( vec, vecLen, originalIncident,
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targetNucleus, theAtomicMass, massVec );
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theParticleChange.SetStatusChange( fStopAndKill );
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theParticleChange.SetEnergyChange( 0.0 );
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theParticleChange.SetNumberOfSecondaries( vecLen );
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G4DynamicParticle * pd;
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for( G4int i=0; i<vecLen; ++i )
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{
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pd = new G4DynamicParticle();
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pd->SetDefinition( vec[i]->GetDefinition() );
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pd->SetMomentum( vec[i]->GetMomentum() );
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theParticleChange.AddSecondary( pd );
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}
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}
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void
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G4LENeutronInelastic::Cascade(
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G4FastVector<G4ReactionProduct,128> &vec,
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G4int& vecLen,
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const G4DynamicParticle *originalIncident,
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G4ReactionProduct ¤tParticle,
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G4ReactionProduct &targetParticle,
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G4bool &incidentHasChanged,
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G4bool &targetHasChanged,
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G4bool &quasiElastic )
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{
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// derived from original FORTRAN code CASN by H. Fesefeldt (13-Sep-1987)
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//
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// Neutron undergoes interaction with nucleon within a nucleus. Check if it is
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// energetically possible to produce pions/kaons. In not, assume nuclear excitation
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// occurs and input particle is degraded in energy. No other particles are produced.
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// If reaction is possible, find the correct number of pions/protons/neutrons
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// produced using an interpolation to multiplicity data. Replace some pions or
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// protons/neutrons by kaons or strange baryons according to the average
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// multiplicity per Inelastic reaction.
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//
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const G4double mOriginal = originalIncident->GetDefinition()->GetPDGMass()/MeV;
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const G4double etOriginal = originalIncident->GetTotalEnergy()/MeV;
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const G4double targetMass = targetParticle.GetMass()/MeV;
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G4double centerofmassEnergy = sqrt( mOriginal*mOriginal +
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targetMass*targetMass +
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2.0*targetMass*etOriginal );
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G4double availableEnergy = centerofmassEnergy-(targetMass+mOriginal);
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if( availableEnergy <= G4PionPlus::PionPlus()->GetPDGMass()/MeV )
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{
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quasiElastic = true;
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return;
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}
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static G4bool first = true;
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const G4int numMul = 1200;
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const G4int numSec = 60;
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static G4double protmul[numMul], protnorm[numSec]; // proton constants
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static G4double neutmul[numMul], neutnorm[numSec]; // neutron constants
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// np = number of pi+, nm = number of pi-, nz = number of pi0
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G4int counter, nt=0, np=0, nm=0, nz=0;
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const G4double c = 1.25;
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const G4double b[] = { 0.35, 0.0 };
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if( first ) // compute normalization constants, this will only be Done once
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{
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first = false;
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G4int i;
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for( i=0; i<numMul; ++i )protmul[i] = 0.0;
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for( i=0; i<numSec; ++i )protnorm[i] = 0.0;
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counter = -1;
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for( np=0; np<numSec/3; ++np )
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{
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for( nm=G4std::max(0,np-1); nm<=(np+1); ++nm )
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{
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for( nz=0; nz<numSec/3; ++nz )
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{
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if( ++counter < numMul )
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{
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nt = np+nm+nz;
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if( nt > 0 )
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{
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protmul[counter] = Pmltpc(np,nm,nz,nt,b[0],c) /
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( theReactionDynamics.Factorial(1-np+nm)*
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theReactionDynamics.Factorial(1+np-nm) );
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protnorm[nt-1] += protmul[counter];
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}
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}
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}
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}
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}
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for( i=0; i<numMul; ++i )neutmul[i] = 0.0;
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for( i=0; i<numSec; ++i )neutnorm[i] = 0.0;
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counter = -1;
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for( np=0; np<(numSec/3); ++np )
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{
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for( nm=np; nm<=(np+2); ++nm )
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{
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for( nz=0; nz<numSec/3; ++nz )
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{
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if( ++counter < numMul )
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{
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nt = np+nm+nz;
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if( (nt>0) && (nt<=numSec) )
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{
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neutmul[counter] = Pmltpc(np,nm,nz,nt,b[1],c) /
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( theReactionDynamics.Factorial(nm-np)*
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theReactionDynamics.Factorial(2-nm+np) );
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neutnorm[nt-1] += neutmul[counter];
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}
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}
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}
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}
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}
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for( i=0; i<numSec; ++i )
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{
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if( protnorm[i] > 0.0 )protnorm[i] = 1.0/protnorm[i];
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if( neutnorm[i] > 0.0 )neutnorm[i] = 1.0/neutnorm[i];
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}
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} // end of initialization
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const G4double expxu = 82.; // upper bound for arg. of exp
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const G4double expxl = -expxu; // lower bound for arg. of exp
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G4ParticleDefinition *aNeutron = G4Neutron::Neutron();
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G4ParticleDefinition *aProton = G4Proton::Proton();
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G4int ieab = availableEnergy*5.0/GeV;
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const G4double supp[] = {0.,0.4,0.55,0.65,0.75,0.82,0.86,0.90,0.94,0.98};
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G4double test, w0, wp, wt, wm;
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if( (availableEnergy < 2.0*GeV) && (G4UniformRand() >= supp[ieab]) )
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{
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// suppress high multiplicity events at low momentum
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// only one pion will be produced
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nm = np = nz = 0;
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if( targetParticle.GetDefinition() == aNeutron )
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{
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test = exp( G4std::min( expxu, G4std::max( expxl, -(1.0+b[1])*(1.0+b[1])/(2.0*c*c) ) ) );
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w0 = test/2.0;
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wm = test;
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if( G4UniformRand() < w0/(w0+wm) )
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nz = 1;
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else
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nm = 1;
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} else { // target is a proton
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test = exp( G4std::min( expxu, G4std::max( expxl, -(1.0+b[0])*(1.0+b[0])/(2.0*c*c) ) ) );
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w0 = test;
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wp = test/2.0;
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test = exp( G4std::min( expxu, G4std::max( expxl, -(-1.0+b[0])*(-1.0+b[0])/(2.0*c*c) ) ) );
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wm = test/2.0;
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wt = w0+wp+wm;
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wp += w0;
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G4double ran = G4UniformRand();
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if( ran < w0/wt )
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nz = 1;
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else if( ran < wp/wt )
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np = 1;
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else
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nm = 1;
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}
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} else { // (availableEnergy >= 2.0*GeV) || (random number < supp[ieab])
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G4double n, anpn;
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GetNormalizationConstant( availableEnergy, n, anpn );
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G4double ran = G4UniformRand();
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G4double dum, excs = 0.0;
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if( targetParticle.GetDefinition() == aProton )
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{
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counter = -1;
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for( np=0; np<numSec/3 && ran>=excs; ++np )
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{
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for( nm=G4std::max(0,np-1); nm<=(np+1) && ran>=excs; ++nm )
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{
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for( nz=0; nz<numSec/3 && ran>=excs; ++nz )
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{
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if( ++counter < numMul )
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{
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nt = np+nm+nz;
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if( nt > 0 )
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{
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test = exp( G4std::min( expxu, G4std::max( expxl, -(pi/4.0)*(nt*nt)/(n*n) ) ) );
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dum = (pi/anpn)*nt*protmul[counter]*protnorm[nt-1]/(2.0*n*n);
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if( fabs(dum) < 1.0 ) {
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if( test >= 1.0e-10 )excs += dum*test;
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} else {
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excs += dum*test;
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}
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}
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}
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}
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}
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}
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if( ran >= excs ) // 3 previous loops continued to the end
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{
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quasiElastic = true;
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return;
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}
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np--; nm--; nz--;
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} else { // target must be a neutron
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counter = -1;
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for( np=0; np<numSec/3 && ran>=excs; ++np )
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{
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for( nm=np; nm<=(np+2) && ran>=excs; ++nm )
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{
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for( nz=0; nz<numSec/3 && ran>=excs; ++nz )
|
|
{
|
|
if( ++counter < numMul )
|
|
{
|
|
nt = np+nm+nz;
|
|
if( (nt>=1) && (nt<=numSec) )
|
|
{
|
|
test = exp( G4std::min( expxu, G4std::max( expxl, -(pi/4.0)*(nt*nt)/(n*n) ) ) );
|
|
dum = (pi/anpn)*nt*neutmul[counter]*neutnorm[nt-1]/(2.0*n*n);
|
|
if( fabs(dum) < 1.0 ) {
|
|
if( test >= 1.0e-10 )excs += dum*test;
|
|
} else {
|
|
excs += dum*test;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
if( ran >= excs ) // 3 previous loops continued to the end
|
|
{
|
|
quasiElastic = true;
|
|
return;
|
|
}
|
|
np--; nm--; nz--;
|
|
}
|
|
}
|
|
if( targetParticle.GetDefinition() == aProton )
|
|
{
|
|
switch( np-nm )
|
|
{
|
|
case 0:
|
|
if( G4UniformRand() < 0.33 )
|
|
{
|
|
currentParticle.SetDefinitionAndUpdateE( aProton );
|
|
targetParticle.SetDefinitionAndUpdateE( aNeutron );
|
|
incidentHasChanged = true;
|
|
targetHasChanged = true;
|
|
}
|
|
break;
|
|
case 1:
|
|
targetParticle.SetDefinitionAndUpdateE( aNeutron );
|
|
targetHasChanged = true;
|
|
break;
|
|
default:
|
|
currentParticle.SetDefinitionAndUpdateE( aProton );
|
|
incidentHasChanged = true;
|
|
break;
|
|
}
|
|
} else { // target must be a neutron
|
|
switch( np-nm )
|
|
{
|
|
case -1: // changed from +1 by JLC, 7Jul97
|
|
if( G4UniformRand() < 0.5 )
|
|
{
|
|
currentParticle.SetDefinitionAndUpdateE( aProton );
|
|
incidentHasChanged = true;
|
|
} else {
|
|
targetParticle.SetDefinitionAndUpdateE( aProton );
|
|
targetHasChanged = true;
|
|
}
|
|
break;
|
|
case 0:
|
|
break;
|
|
default:
|
|
currentParticle.SetDefinitionAndUpdateE( aProton );
|
|
targetParticle.SetDefinitionAndUpdateE( aProton );
|
|
incidentHasChanged = true;
|
|
targetHasChanged = true;
|
|
break;
|
|
}
|
|
}
|
|
SetUpPions( np, nm, nz, vec, vecLen );
|
|
// DEBUG --> DumpFrames::DumpFrame(vec, vecLen);
|
|
return;
|
|
}
|
|
|
|
/* end of file */
|
|
|