LaserBeamsTEC2.cc

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#include "Alignment/LaserAlignmentSimulation/interface/LaserBeamsTEC2.h"

#include "FWCore/MessageLogger/interface/MessageLogger.h"
#include "FWCore/ServiceRegistry/interface/Service.h"
#include "FWCore/Utilities/interface/RandomNumberGenerator.h"

#include <CLHEP/Random/RandGaussQ.h>
#include <CLHEP/Units/SystemOfUnits.h>
#include "G4ParticleDefinition.hh"
#include "G4ParticleGun.hh"
#include "globals.hh"  // Global Constants and typedefs

LaserBeamsTEC2::LaserBeamsTEC2() : theParticleGun(nullptr), theDRand48Engine(nullptr) {
  G4int nPhotonsGun = 1;
  G4int nPhotonsBeam = 1;
  G4double Energy = 1.15 * CLHEP::eV;
  // call constructor with options
  LaserBeamsTEC2(nPhotonsGun, nPhotonsBeam, Energy);
}

LaserBeamsTEC2::LaserBeamsTEC2(G4int nPhotonsInGun, G4int nPhotonsInBeam, G4double PhotonEnergy)
    : thenParticleInGun(0), thenParticle(0), thePhotonEnergy(0), theParticleGun(), theDRand48Engine() {
  /* *********************************************************************** */
  /*  initialize and configure the particle gun                              */
  /* *********************************************************************** */

  // the Photon energy
  thePhotonEnergy = PhotonEnergy;

  // number of particles in the Laser beam
  thenParticleInGun = nPhotonsInGun;

  // number of particles in one beam. ATTENTION: each beam contains
  // nParticleInGun with the same startpoint and direction. nParticle gives the
  // number of particles in the beam with a different startpoint. They are used
  // to simulate the gaussian beamprofile of the Laser Beams.
  thenParticle = nPhotonsInBeam;

  // create the particle gun
  theParticleGun = new G4ParticleGun(thenParticleInGun);

  // default kinematics
  G4ParticleTable *theParticleTable = G4ParticleTable::GetParticleTable();
  G4ParticleDefinition *theOpticalPhoton = theParticleTable->FindParticle("opticalphoton");

  theParticleGun->SetParticleDefinition(theOpticalPhoton);
  theParticleGun->SetParticleTime(0.0 * CLHEP::ns);
  theParticleGun->SetParticlePosition(G4ThreeVector(-500.0 * CLHEP::cm, 0.0 * CLHEP::cm, 0.0 * CLHEP::cm));
  theParticleGun->SetParticleMomentumDirection(G4ThreeVector(5.0, 3.0, 0.0));
  theParticleGun->SetParticleEnergy(10.0 * CLHEP::keV);
  setOptPhotonPolar(90.0);

  // initialize the random number engine
  theDRand48Engine = new CLHEP::DRand48Engine();
}

LaserBeamsTEC2::~LaserBeamsTEC2() {
  if (theParticleGun != nullptr) {
    delete theParticleGun;
  }
  if (theDRand48Engine != nullptr) {
    delete theDRand48Engine;
  }
}

void LaserBeamsTEC2::GeneratePrimaries(G4Event *myEvent) {
  // this function is called at the beginning of an Event in
  // LaserAlignment::upDate(const BeginOfEvent * myEvent)

  // use the random number generator service of the framework
  edm::Service<edm::RandomNumberGenerator> rng;
  unsigned int seed = rng->mySeed();

  // set the seed
  theDRand48Engine->setSeed(seed);

  // number of LaserRings and Laserdiodes
  const G4int nLaserRings = 2;
  const G4int nLaserBeams = 8;

  // z position of the sixth Tracker Endcap Disc, where the Laserdiodes are
  // positioned
  using CLHEP::mm;
  G4double LaserPositionZ = -2057.5 * mm;

  // Radius of the inner and outer Laser ring
  G4double LaserRingRadius[nLaserRings] = {564.0 * mm, 840.0 * mm};

  // phi position of the first Laserdiode
  G4double LaserPhi0 = 0.392699082;

  // width of the LaserBeams
  G4double LaserRingSigmaX[nLaserRings] = {0.5 * mm, 0.5 * mm};
  G4double LaserRingSigmaY[nLaserRings] = {0.5 * mm, 0.5 * mm};

  // get the definition of the optical photon
  G4ParticleTable *theParticleTable = G4ParticleTable::GetParticleTable();
  G4ParticleDefinition *theOpticalPhoton = theParticleTable->FindParticle("opticalphoton");

  // loop over the LaserRings
  for (int theRing = 0; theRing < nLaserRings; theRing++) {
    // loop over the LaserBeams
    for (int theBeam = 0; theBeam < nLaserBeams; theBeam++) {
      // code for forward and backward beam
      // calculate the right phi for the current beam
      G4double LaserPositionPhi = LaserPhi0 + G4double(theBeam * G4double(G4double(2 * M_PI) / nLaserBeams));

      // calculate x and y position for the current beam
      G4double LaserPositionX = cos(LaserPositionPhi) * LaserRingRadius[theRing];
      G4double LaserPositionY = sin(LaserPositionPhi) * LaserRingRadius[theRing];

      // loop over all the particles in one beam
      for (int theParticle = 0; theParticle < thenParticle; theParticle++) {
        // get randomnumbers  and calculate the position
        CLHEP::RandGaussQ aGaussObjX(*theDRand48Engine, LaserPositionX, LaserRingSigmaX[theRing]);
        CLHEP::RandGaussQ aGaussObjY(*theDRand48Engine, LaserPositionY, LaserRingSigmaY[theRing]);

        G4double theXPosition = aGaussObjX.fire();
        G4double theYPosition = aGaussObjY.fire();
        G4double theZPosition = LaserPositionZ;

        // set the properties of the newly created particle
        theParticleGun->SetParticleDefinition(theOpticalPhoton);
        theParticleGun->SetParticleTime(0.0 * CLHEP::ns);
        theParticleGun->SetParticlePosition(G4ThreeVector(theXPosition, theYPosition, theZPosition));
        theParticleGun->SetParticleEnergy(thePhotonEnergy);

        // loop over both directions of the beam
        for (int theDirection = 0; theDirection < 2; theDirection++) {
          // shoot in both beam directions ...
          if (theDirection == 0)  // shoot in forward direction (+z)
          {
            theParticleGun->SetParticleMomentumDirection(G4ThreeVector(0.0, 0.0, 1.0));
            // set the polarization
            setOptPhotonPolar(90.0);
            // generate the particle
            theParticleGun->GeneratePrimaryVertex(myEvent);
          }

          if (theDirection == 1)  // shoot in backward direction (-z)
          {
            theParticleGun->SetParticleMomentumDirection(G4ThreeVector(0.0, 0.0, -1.0));
            // set the polarization
            setOptPhotonPolar(90.0);
            // generate the particle
            theParticleGun->GeneratePrimaryVertex(myEvent);
          }
        }  // end loop over both beam directions
      }    // end loop over particles in beam
    }      // end loop over beams
  }        // end loop over rings
}

void LaserBeamsTEC2::setOptPhotonPolar(G4double Angle) {
  /* *********************************************************************** */
  /*   to get optical processes working properly, you have to make sure      *
   *   that the photon polarisation is defined.                              */
  /* *********************************************************************** */

  // first check if we have an optical photon
  if (theParticleGun->GetParticleDefinition()->GetParticleName() != "opticalphoton") {
    edm::LogWarning("SimLaserAlignment:LaserBeamsTEC2")
        << "<LaserBeamsTEC2::setOptPhotonPolar()>: WARNING! The ParticleGun is "
           "not an optical photon";
    return;
  }

  //   G4cout << "  AC1CMS: The ParticleGun is an " <<
  //   theParticleGun->GetParticleDefinition()->GetParticleName();
  G4ThreeVector normal(1.0, 0.0, 0.0);
  G4ThreeVector kphoton = theParticleGun->GetParticleMomentumDirection();
  G4ThreeVector product = normal.cross(kphoton);
  G4double modul2 = product * product;

  G4ThreeVector e_perpendicular(0.0, 0.0, 1.0);

  if (modul2 > 0.0) {
    e_perpendicular = (1.0 / sqrt(modul2)) * product;
  }

  G4ThreeVector e_parallel = e_perpendicular.cross(kphoton);

  G4ThreeVector polar = cos(Angle) * e_parallel + sin(Angle) * e_perpendicular;

  //   G4cout << ", the polarization = " << polar << G4endl;
  theParticleGun->SetParticlePolarization(polar);
}