G4SynchrotronRadiation.cc

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//
// $Id$
//
// --------------------------------------------------------------
//      GEANT 4 class implementation file
//      CERN Geneva Switzerland
//
//      History: first implementation, 
//      21-5-98 V.Grichine
//      28-05-01, V.Ivanchenko minor changes to provide ANSI -wall compilation 
//      04.03.05, V.Grichine: get local field interface      
//      18-05-06 H. Burkhardt: Energy spectrum from function rather than table
//                    
// 
//
//
///////////////////////////////////////////////////////////////////////////
 
#include "G4SynchrotronRadiation.hh"
#include "G4PhysicalConstants.hh"
#include "G4SystemOfUnits.hh"
#include "G4UnitsTable.hh"
#include "G4EmProcessSubType.hh"
 
///////////////////////////////////////////////////////////////////////
//
//  Constructor
//
 
G4SynchrotronRadiation::G4SynchrotronRadiation(const G4String& processName,
  G4ProcessType type):G4VDiscreteProcess (processName, type),
  theGamma (G4Gamma::Gamma() ),
  theElectron ( G4Electron::Electron() ),
  thePositron ( G4Positron::Positron() )
{
  G4TransportationManager* transportMgr = 
    G4TransportationManager::GetTransportationManager();
 
  fFieldPropagator = transportMgr->GetPropagatorInField();
 
  fLambdaConst = std::sqrt(3.0)*electron_mass_c2/
                           (2.5*fine_structure_const*eplus*c_light);
  fEnergyConst = 1.5*c_light*c_light*eplus*hbar_Planck/electron_mass_c2 ;
 
  SetProcessSubType(fSynchrotronRadiation);
  verboseLevel=1;
}
 
/////////////////////////////////////////////////////////////////////////
//
// Destructor
//
 
G4SynchrotronRadiation::~G4SynchrotronRadiation()
{}
 
/////////////////////////////// METHODS /////////////////////////////////
//
//
// Production of synchrotron X-ray photon
// GEANT4 internal units.
//
 
 
G4double
G4SynchrotronRadiation::GetMeanFreePath( const G4Track& trackData,
                                               G4double,
                                               G4ForceCondition* condition)
{
  // gives the MeanFreePath in GEANT4 internal units
  G4double MeanFreePath;
 
  const G4DynamicParticle* aDynamicParticle = trackData.GetDynamicParticle();
 
  *condition = NotForced;
 
  G4double gamma = aDynamicParticle->GetTotalEnergy()/
                   aDynamicParticle->GetMass();
 
  G4double particleCharge = aDynamicParticle->GetDefinition()->GetPDGCharge();
 
  if ( gamma < 1.0e3 )  MeanFreePath = DBL_MAX;
  else
  {
 
    G4ThreeVector  FieldValue;
    const G4Field*   pField = 0;
 
    G4FieldManager* fieldMgr=0;
    G4bool          fieldExertsForce = false;
 
    if( (particleCharge != 0.0) )
    {
      fieldMgr = fFieldPropagator->FindAndSetFieldManager( trackData.GetVolume() );
 
      if ( fieldMgr != 0 )
      {
        // If the field manager has no field, there is no field !
 
        fieldExertsForce = ( fieldMgr->GetDetectorField() != 0 );
      }
    }
    if ( fieldExertsForce )
    {
      pField = fieldMgr->GetDetectorField();
      G4ThreeVector  globPosition = trackData.GetPosition();
 
      G4double  globPosVec[4], FieldValueVec[6];
 
      globPosVec[0] = globPosition.x();
      globPosVec[1] = globPosition.y();
      globPosVec[2] = globPosition.z();
      globPosVec[3] = trackData.GetGlobalTime();
 
      pField->GetFieldValue( globPosVec, FieldValueVec );
 
      FieldValue = G4ThreeVector( FieldValueVec[0],
                                   FieldValueVec[1],
                                   FieldValueVec[2]   );
 
 
 
      G4ThreeVector unitMomentum = aDynamicParticle->GetMomentumDirection();
      G4ThreeVector unitMcrossB  = FieldValue.cross(unitMomentum);
      G4double perpB             = unitMcrossB.mag();
 
      if( perpB > 0.0 ) MeanFreePath = fLambdaConst/perpB;
      else              MeanFreePath = DBL_MAX;
 
      static G4bool FirstTime=true;
      if(verboseLevel > 0 && FirstTime)
      {
        G4cout << "G4SynchrotronRadiation::GetMeanFreePath :" << '\n' 
           << "  MeanFreePath = " << G4BestUnit(MeanFreePath, "Length")
           << G4endl;
        if(verboseLevel > 1)
        {
          G4ThreeVector pvec=aDynamicParticle->GetMomentum();
          G4double Btot=FieldValue.getR();
          G4double ptot=pvec.getR();
          G4double rho= ptot / (MeV * c_light * Btot ); // full bending radius
          G4double Theta=unitMomentum.theta(FieldValue); // angle between particle and field
          G4cout
            << "  B = " << Btot/tesla << " Tesla"
            << "  perpB = " << perpB/tesla << " Tesla"
            << "  Theta = " << Theta << " std::sin(Theta)=" << std::sin(Theta) << '\n'
            << "  ptot  = " << G4BestUnit(ptot,"Energy")
            << "  rho   = " << G4BestUnit(rho,"Length")
            << G4endl;
        }
    FirstTime=false;
      }
    }
    else  MeanFreePath = DBL_MAX;
 
 
  }
 
  return MeanFreePath;
}
 
////////////////////////////////////////////////////////////////////////////////
//
//
 
G4VParticleChange* 
G4SynchrotronRadiation::PostStepDoIt(const G4Track& trackData,
                                     const G4Step&  stepData      )
 
{
  aParticleChange.Initialize(trackData);
 
  const G4DynamicParticle* aDynamicParticle=trackData.GetDynamicParticle();
 
  G4double gamma = aDynamicParticle->GetTotalEnergy()/
                   (aDynamicParticle->GetMass()              );
 
  if(gamma <= 1.0e3 ) 
  {
    return G4VDiscreteProcess::PostStepDoIt(trackData,stepData);
  }
  G4double particleCharge = aDynamicParticle->GetDefinition()->GetPDGCharge();
 
  G4ThreeVector  FieldValue;
  const G4Field*   pField = 0;
 
  G4FieldManager* fieldMgr=0;
  G4bool          fieldExertsForce = false;
 
  if( (particleCharge != 0.0) )
  {
    fieldMgr = fFieldPropagator->FindAndSetFieldManager( trackData.GetVolume() );
    if ( fieldMgr != 0 )
    {
      // If the field manager has no field, there is no field !
 
      fieldExertsForce = ( fieldMgr->GetDetectorField() != 0 );
    }
  }
  if ( fieldExertsForce )
  {
    pField = fieldMgr->GetDetectorField();
    G4ThreeVector  globPosition = trackData.GetPosition();
    G4double  globPosVec[4], FieldValueVec[6];
    globPosVec[0] = globPosition.x();
    globPosVec[1] = globPosition.y();
    globPosVec[2] = globPosition.z();
    globPosVec[3] = trackData.GetGlobalTime();
 
    pField->GetFieldValue( globPosVec, FieldValueVec );
    FieldValue = G4ThreeVector( FieldValueVec[0],
                                   FieldValueVec[1],
                                   FieldValueVec[2]   );
 
    G4ThreeVector unitMomentum = aDynamicParticle->GetMomentumDirection();
    G4ThreeVector unitMcrossB = FieldValue.cross(unitMomentum);
    G4double perpB = unitMcrossB.mag();
    if(perpB > 0.0)
    {
      // M-C of synchrotron photon energy
 
      G4double energyOfSR = GetRandomEnergySR(gamma,perpB);
 
      // check against insufficient energy
 
      if( energyOfSR <= 0.0 )
      {
        return G4VDiscreteProcess::PostStepDoIt(trackData,stepData);
      }
      G4double kineticEnergy = aDynamicParticle->GetKineticEnergy();
      G4ParticleMomentum
      particleDirection = aDynamicParticle->GetMomentumDirection();
 
      // M-C of its direction, simplified dipole boosted approach
 
      // G4double Teta, fteta;  // = G4UniformRand()/gamma;    // Very roughly
 
      G4double cosTheta, sinTheta, fcos, beta;
 
  do
  { 
    cosTheta = 1. - 2.*G4UniformRand();
    fcos     = (1 + cosTheta*cosTheta)*0.5;
  }
  while( fcos < G4UniformRand() );
 
  beta = std::sqrt(1. - 1./(gamma*gamma));
 
  cosTheta = (cosTheta + beta)/(1. + beta*cosTheta);
 
  if( cosTheta >  1. ) cosTheta =  1.;
  if( cosTheta < -1. ) cosTheta = -1.;
 
  sinTheta = std::sqrt(1. - cosTheta*cosTheta );
 
      G4double Phi  = twopi * G4UniformRand();
 
      G4double dirx = sinTheta*std::cos(Phi) ,
               diry = sinTheta*std::sin(Phi) ,
               dirz = cosTheta;
 
      G4ThreeVector gammaDirection ( dirx, diry, dirz);
      gammaDirection.rotateUz(particleDirection);
 
      // polarization of new gamma
 
      // G4double sx =  std::cos(Teta)*std::cos(Phi);
      // G4double sy =  std::cos(Teta)*std::sin(Phi);
      // G4double sz = -std::sin(Teta);
 
      G4ThreeVector gammaPolarization = FieldValue.cross(gammaDirection);
      gammaPolarization = gammaPolarization.unit();
 
      // (sx, sy, sz);
      // gammaPolarization.rotateUz(particleDirection);
 
      // create G4DynamicParticle object for the SR photon
 
      G4DynamicParticle* aGamma= new G4DynamicParticle ( theGamma,
                                                         gammaDirection,
                                                         energyOfSR      );
      aGamma->SetPolarization( gammaPolarization.x(),
                               gammaPolarization.y(),
                               gammaPolarization.z() );
 
 
      aParticleChange.SetNumberOfSecondaries(1);
      aParticleChange.AddSecondary(aGamma);
 
      // Update the incident particle
 
      G4double newKinEnergy = kineticEnergy - energyOfSR;
      aParticleChange.ProposeLocalEnergyDeposit (0.);
 
      if (newKinEnergy > 0.)
      {
        aParticleChange.ProposeMomentumDirection( particleDirection );
        aParticleChange.ProposeEnergy( newKinEnergy );
      }
      else
      {
        aParticleChange.ProposeEnergy( 0. );
      }
    }
  }
  return G4VDiscreteProcess::PostStepDoIt(trackData,stepData);
}
 
 
/////////////////////////////////////////////////////////////////////////////////
//
//
 
G4double G4SynchrotronRadiation::InvSynFracInt(G4double x)
// direct generation
{
  // from 0 to 0.7
  const G4double aa1=0  ,aa2=0.7;
  const G4int ncheb1=27;
  static const G4double cheb1[] =
  { 1.22371665676046468821,0.108956475422163837267,0.0383328524358594396134,0.00759138369340257753721,
   0.00205712048644963340914,0.000497810783280019308661,0.000130743691810302187818,0.0000338168760220395409734,
   8.97049680900520817728e-6,2.38685472794452241466e-6,6.41923109149104165049e-7,1.73549898982749277843e-7,
   4.72145949240790029153e-8,1.29039866111999149636e-8,3.5422080787089834182e-9,9.7594757336403784905e-10,
   2.6979510184976065731e-10,7.480422622550977077e-11,2.079598176402699913e-11,5.79533622220841193e-12,
   1.61856011449276096e-12,4.529450993473807e-13,1.2698603951096606e-13,3.566117394511206e-14,1.00301587494091e-14,
   2.82515346447219e-15,7.9680747949792e-16};
  //   from 0.7 to 0.9132260271183847
  const G4double aa3=0.9132260271183847;
  const G4int ncheb2=27;
  static const G4double cheb2[] =
  { 1.1139496701107756,0.3523967429328067,0.0713849171926623,0.01475818043595387,0.003381255637322462,
    0.0008228057599452224,0.00020785506681254216,0.00005390169253706556,0.000014250571923902464,3.823880733161044e-6,
    1.0381966089136036e-6,2.8457557457837253e-7,7.86223332179956e-8,2.1866609342508474e-8,6.116186259857143e-9,
    1.7191233618437565e-9,4.852755117740807e-10,1.3749966961763457e-10,3.908961987062447e-11,1.1146253766895824e-11,
    3.1868887323415814e-12,9.134319791300977e-13,2.6211077371181566e-13,7.588643377757906e-14,2.1528376972619e-14,
    6.030906040404772e-15,1.9549163926819867e-15};
   // Chebyshev with exp/log  scale
   // a = -Log[1 - SynFracInt[1]]; b = -Log[1 - SynFracInt[7]];
  const G4double aa4=2.4444485538746025480,aa5=9.3830728608909477079;
  const G4int ncheb3=28;
  static const G4double cheb3[] =
  { 1.2292683840435586977,0.160353449247864455879,-0.0353559911947559448721,0.00776901561223573936985,
   -0.00165886451971685133259,0.000335719118906954279467,-0.0000617184951079161143187,9.23534039743246708256e-6,
   -6.06747198795168022842e-7,-3.07934045961999778094e-7,1.98818772614682367781e-7,-8.13909971567720135413e-8,
   2.84298174969641838618e-8,-9.12829766621316063548e-9,2.77713868004820551077e-9,-8.13032767247834023165e-10,
   2.31128525568385247392e-10,-6.41796873254200220876e-11,1.74815310473323361543e-11,-4.68653536933392363045e-12,
   1.24016595805520752748e-12,-3.24839432979935522159e-13,8.44601465226513952994e-14,-2.18647276044246803998e-14,
   5.65407548745690689978e-15,-1.46553625917463067508e-15,3.82059606377570462276e-16,-1.00457896653436912508e-16};
  const G4double aa6=33.122936966163038145;
  const G4int ncheb4=27;
  static const G4double cheb4[] =
  {1.69342658227676741765,0.0742766400841232319225,-0.019337880608635717358,0.00516065527473364110491,
   -0.00139342012990307729473,0.000378549864052022522193,-0.000103167085583785340215,0.0000281543441271412178337,
   -7.68409742018258198651e-6,2.09543221890204537392e-6,-5.70493140367526282946e-7,1.54961164548564906446e-7,
   -4.19665599629607704794e-8,1.13239680054166507038e-8,-3.04223563379021441863e-9,8.13073745977562957997e-10,
   -2.15969415476814981374e-10,5.69472105972525594811e-11,-1.48844799572430829499e-11,3.84901514438304484973e-12,
   -9.82222575944247161834e-13,2.46468329208292208183e-13,-6.04953826265982691612e-14,1.44055805710671611984e-14,
   -3.28200813577388740722e-15,6.96566359173765367675e-16,-1.294122794852896275e-16};
 
  if(x<aa2)      return x*x*x*Chebyshev(aa1,aa2,cheb1,ncheb1,x);
  else if(x<aa3) return       Chebyshev(aa2,aa3,cheb2,ncheb2,x);
  else if(x<1-0.0000841363)
  { G4double y=-std::log(1-x);
    return y*Chebyshev(aa4,aa5,cheb3,ncheb3,y);
  }
  else
  { G4double y=-std::log(1-x);
    return y*Chebyshev(aa5,aa6,cheb4,ncheb4,y);
  }
}
 
G4double G4SynchrotronRadiation::GetRandomEnergySR(G4double gamma, G4double perpB)
{
 
  G4double Ecr=fEnergyConst*gamma*gamma*perpB;
 
  static G4bool FirstTime=true;
  if(verboseLevel > 0 && FirstTime)
  { G4double Emean=8./(15.*std::sqrt(3.))*Ecr; // mean photon energy
    G4double E_rms=std::sqrt(211./675.)*Ecr; // rms of photon energy distribution
    G4int prec = G4cout.precision();
    G4cout << "G4SynchrotronRadiation::GetRandomEnergySR :" << '\n' << std::setprecision(4)
    << "  Ecr   = "    << G4BestUnit(Ecr,"Energy") << '\n'
    << "  Emean = "    << G4BestUnit(Emean,"Energy") << '\n'
    << "  E_rms = "    << G4BestUnit(E_rms,"Energy") << G4endl;
    FirstTime=false;
    G4cout.precision(prec); 
  }
 
  G4double energySR=Ecr*InvSynFracInt(G4UniformRand());
  return energySR;
}
 
 
void G4SynchrotronRadiation::BuildPhysicsTable(const G4ParticleDefinition& part)
{
  if(0 < verboseLevel && &part==theElectron ) PrintInfoDefinition();
}
 
void G4SynchrotronRadiation::PrintInfoDefinition() // not yet called, usually called from BuildPhysicsTable
{
  G4String comments ="Incoherent Synchrotron Radiation\n";
  G4cout << G4endl << GetProcessName() << ":  " << comments
         << "      good description for long magnets at all energies" << G4endl;
}
 
///////////////////// end of G4SynchrotronRadiation.cc