G4SynchrotronRadiation.cc

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// $Id: G4SynchrotronRadiation.cc 97385 2016-06-02 09:59:53Z gcosmo $
//
// --------------------------------------------------------------
//      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"
#include "G4DipBustGenerator.hh"
#include "G4Log.hh"

//
//  Constructor
//

G4SynchrotronRadiation::G4SynchrotronRadiation(const G4String& processName,
  G4ProcessType type):G4VDiscreteProcess (processName, type),
  theGamma (G4Gamma::Gamma() ) 
{
  G4TransportationManager* transportMgr = 
    G4TransportationManager::GetTransportationManager();

  fFieldPropagator = transportMgr->GetPropagatorInField();

  SetProcessSubType(fSynchrotronRadiation);
  verboseLevel = 1;
  FirstTime    = true;
  FirstTime1   = true;
  genAngle     = nullptr;
  SetAngularGenerator(new G4DipBustGenerator());
}

//
// Destructor
//

G4SynchrotronRadiation::~G4SynchrotronRadiation()
{
    delete genAngle;
}

//

void 
G4SynchrotronRadiation::SetAngularGenerator(G4VEmAngularDistribution* p)
{
  if(p != genAngle) {
    delete genAngle;
    genAngle = p;
  }
}

G4bool
G4SynchrotronRadiation::IsApplicable(const G4ParticleDefinition& particle)
{
  return (particle.GetPDGCharge() != 0.0 && !particle.IsShortLived()); 
}

//
// 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 = DBL_MAX;

  const G4DynamicParticle* aDynamicParticle = trackData.GetDynamicParticle();

  *condition = NotForced;

  G4double gamma = aDynamicParticle->GetTotalEnergy()/
                   aDynamicParticle->GetMass();

  G4double particleCharge = aDynamicParticle->GetDefinition()->GetPDGCharge();

  if ( gamma < 1.0e3 || 0.0 == particleCharge)  { MeanFreePath = DBL_MAX; }
  else
  {

    G4ThreeVector  FieldValue;
    const G4Field* pField = nullptr;
    G4bool         fieldExertsForce = false;


    G4FieldManager* fieldMgr = 
        fFieldPropagator->FindAndSetFieldManager(trackData.GetVolume());

    if ( fieldMgr != nullptr )
    {
      // If the field manager has no field, there is no field !

      fieldExertsForce = ( fieldMgr->GetDetectorField() != nullptr );
    }
   
    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();

      static const G4double fLambdaConst = std::sqrt(3.0)*eplus/
        (2.5*fine_structure_const*c_light); 
          
      if( perpB > 0.0 )
      {
        MeanFreePath = 
          fLambdaConst*aDynamicParticle->GetDefinition()->GetPDGMass()
          /(perpB*particleCharge*particleCharge);
      }
      if(verboseLevel > 0 && FirstTime)
      {
        G4cout << "G4SynchrotronRadiation::GetMeanFreePath "
               << " for particle " 
               << aDynamicParticle->GetDefinition()->GetParticleName() 
               << ":" << '\n'  //hbunew
               << "  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;
      }
    }
  }
  return MeanFreePath;
}

//
//

G4VParticleChange* 
G4SynchrotronRadiation::PostStepDoIt(const G4Track& trackData,
                                     const G4Step&  stepData      )

{
  aParticleChange.Initialize(trackData);

  const G4DynamicParticle* aDynamicParticle = trackData.GetDynamicParticle();

  G4double gamma = aDynamicParticle->GetTotalEnergy()/
    (aDynamicParticle->GetDefinition()->GetPDGMass());

  G4double particleCharge = aDynamicParticle->GetDefinition()->GetPDGCharge();
  if(gamma <= 1.0e3  || 0.0 == particleCharge) 
  {
    return G4VDiscreteProcess::PostStepDoIt(trackData,stepData);
  }

  G4ThreeVector  FieldValue;
  const G4Field*   pField = nullptr;

  G4bool          fieldExertsForce = false;
  G4FieldManager* fieldMgr = 
    fFieldPropagator->FindAndSetFieldManager(trackData.GetVolume());

  if ( fieldMgr != nullptr )
  {
    // If the field manager has no field, there is no field !
    fieldExertsForce = ( fieldMgr->GetDetectorField() != nullptr );
  }
 
  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,
                          aDynamicParticle->GetDefinition()->GetPDGMass());

      // check against insufficient energy

      if( energyOfSR <= 0.0 )
      {
        return G4VDiscreteProcess::PostStepDoIt(trackData,stepData);
      }
      G4double kineticEnergy = aDynamicParticle->GetKineticEnergy();
      G4ThreeVector gammaDirection = 
        genAngle->SampleDirection(aDynamicParticle,
                                  energyOfSR, 1, 0);

      G4ThreeVector gammaPolarization = FieldValue.cross(gammaDirection);
      gammaPolarization = gammaPolarization.unit();

      // 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;

      if (newKinEnergy > 0.)
      {
        aParticleChange.ProposeEnergy( newKinEnergy );
      }
      else
      {
        aParticleChange.ProposeEnergy( 0. );
      }
    }
  }
  return G4VDiscreteProcess::PostStepDoIt(trackData,stepData);
}

//
//

G4double G4SynchrotronRadiation::InvSynFracInt(G4double x)
// direct generation
{
  // from 0 to 0.7
  static const G4double aa1=0  ,aa2=0.7;
  static 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
  static const G4double aa3=0.9132260271183847;
  static 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]];
  static const G4double aa4=2.4444485538746025480,aa5=9.3830728608909477079;
  static 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};
  static const G4double aa6=33.122936966163038145;
  static 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=-G4Log(1-x);
        return y*Chebyshev(aa4,aa5,cheb3,ncheb3,y);
  }
  else
  { G4double y=-G4Log(1-x);
        return y*Chebyshev(aa5,aa6,cheb4,ncheb4,y);
  }
}

G4double G4SynchrotronRadiation::GetRandomEnergySR(
         G4double gamma, G4double perpB, G4double mass_c2) 
{

  static const G4double fEnergyConst = 1.5*c_light*c_light*eplus*hbar_Planck; 
  G4double Ecr=fEnergyConst*gamma*gamma*perpB/mass_c2;

  if(verboseLevel > 0 && FirstTime1)
  { 
    // mean and rms of photon energy 
    G4double Emean=8./(15.*std::sqrt(3.))*Ecr;
    G4double E_rms=std::sqrt(211./675.)*Ecr; 
    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;
    FirstTime1=false;
    G4cout.precision(prec); 
  }

  G4double energySR=Ecr*InvSynFracInt(G4UniformRand());
  return energySR;
}

//
//

void 
G4SynchrotronRadiation::BuildPhysicsTable(const G4ParticleDefinition& part)
{
  if(0 < verboseLevel && &part==G4Electron::Electron() ) PrintInfoDefinition();
  // same for all particles, print only for one (electron)
}

//
//

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;
}