PndGeoDskFLG.cxx

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// PndGeoDskFLG
//
// Class for geometry of DskFLG
//
// Created 29/04/10 by Y. Liang, Giessen University 
//

#include "PndGeoDskFLG.h"
#include "FairGeoNode.h"

using std::endl;
using std::cout;


ClassImp(PndGeoDskFLG)

// -----   Default constructor   -------------------------------------------
PndGeoDskFLG::PndGeoDskFLG() {
  // Constructor

   fRadius = 1100;// mm, fix me.  need to retrieve from geo in future
   fPosition_plate = 2000; //position of plate, fix me.  need to retrieve from geo in future
   fThickness_plate = 20; //mm, fix me.  need to retrieve from geo in future
   fNumber_focusing_part = 128;// 128 focusing parts, fix me. 
   fReflectThreshold = 0.8;

   a0 = 0.;
   a1 = 0.;
   a2 = -14.37217*1.0E-4;
   a3 = -2.044957*1.0E-6;
   a4 = -1.998331*1.0E-8;
   a5 = -1.109226*1.0E-10;

   fVerbose = 1;  
 }
// -------------------------------------------------------------------------

// --------- Propagate cherenkov photon to focusing light guide
void PndGeoDskFLG::Propagate(TVector3 pos, TVector3 dir,Int_t &i_FLG, Int_t &i_Pixel)
{
  TVector3 Cylinder_point(1,0,0);
  LineCylinderInteraction(pos, dir, Cylinder_point);
  if(fVerbose > 1) cout<<"-I- PndGeoDskFLG::Propagate, Cylinder_point=("<<Cylinder_point.X()<<","<<Cylinder_point.Y()<<","<<Cylinder_point.Z()<<endl;

  //now, need to calc how many folder of this line, the position and direction at the edge of cylinder
  Double_t z_inner_edge_plate = fPosition_plate-fThickness_plate/2;
  Int_t N_reflection = Int_t((Cylinder_point.Z()- z_inner_edge_plate)/fThickness_plate); //from inner side of plate, thickness: 2cm
  Double_t z_plate_edge = (Cylinder_point.Z()-z_inner_edge_plate) - N_reflection*fThickness_plate;
  if(N_reflection%2==1) z_plate_edge = - z_plate_edge; //update start point
  if(fVerbose > 1) cout<<"-I- PndGeoDskFLG::Propagate, N_reflection: "<<N_reflection<<"  z of photon, when penetrates plate: "<<z_plate_edge<<endl;

  Double_t dphi = (TMath::Pi())*2/fNumber_focusing_part;
  Int_t i_phi = Int_t(Cylinder_point.Phi()/dphi);

  if(Cylinder_point.Phi()<0) i_phi = i_phi-1;

  Double_t phi_foucsing_part = i_phi*dphi;
  if(fVerbose > 1) cout<<"-I- PndGeoDskFLG::Propagate, i_phi: "<<i_phi<<"  "<<phi_foucsing_part<<" dphi: "<<dphi<<"   Cylinder_point.Phi(): "<<Cylinder_point.Phi()<<endl;

  //Coordinate transform: global->certain light guide
  TVector3 dir_in_focusing_coor(sin(dir.Theta())*cos(dir.Phi()-phi_foucsing_part), cos(dir.Theta()), sin(dir.Theta())*sin(dir.Phi()-phi_foucsing_part));
  if(fVerbose > 1) cout<<"-I- PndGeoDskFLG::Propagate,theta, phi in new coordinate: "<<dir_in_focusing_coor.Theta()<<"  "<<dir_in_focusing_coor.Phi()<<endl;

  //new way, use TVector3::Rotate()

  //now, propagate in light guide
  TVector3 StartPoint(-70, -55+z_plate_edge, 0); //z = 0 temporary
  Double_t StepLength = 10;  //mm
  if(fVerbose>1){
     cout<<"-I- PndGeoDskFLG::Propagate, start Point: "<<StartPoint.X()<<" "<<StartPoint.Y()<<" "<<StartPoint.Z()<<endl;
  }

  TVector3 Direction = dir_in_focusing_coor;
  if(Direction.Phi()< 25./180*(TMath::Pi()) ||Direction.Phi()>50./180*(TMath::Pi()) ) return; //do not deal with this

  Int_t i_loop = 0, max_loop = 2000;
  TVector3 NextPoint = StartPoint;
  do{
      NextPoint = NextPoint + Direction*StepLength;
      i_loop++;
      if(fVerbose>1)cout<<"NextPoint: "<<NextPoint.X()<<" "<<NextPoint.Y()<<" "<<NextPoint.Z()<<endl;
   }while(CurveFunction(NextPoint)&&i_loop<max_loop);
   NextPoint = NextPoint - Direction*StepLength;  //go back one step

   StepLength /= 10; //0.1mm 
   do{
      NextPoint = NextPoint + Direction*StepLength;
      i_loop++;
      if(fVerbose>1)cout<<"NextPoint: "<<NextPoint.X()<<" "<<NextPoint.Y()<<" "<<NextPoint.Z()<<endl;
   }while(CurveFunction(NextPoint)&&i_loop<max_loop);
   NextPoint = NextPoint - Direction*StepLength;  //go back one step

   StepLength /= 10; //0.01mm 
   do{
      NextPoint = NextPoint + Direction*StepLength;
      i_loop++;
      if(fVerbose>1)cout<<"NextPoint: "<<NextPoint.X()<<" "<<NextPoint.Y()<<" "<<NextPoint.Z()<<endl;
   }while(CurveFunction(NextPoint)&&i_loop<max_loop);
   NextPoint = NextPoint - Direction*StepLength;  //go back one step

   Double_t phi_prime = SlopeCurveFunction(NextPoint);
   Direction.SetPhi( 2*phi_prime - Direction.Phi());
   if(fVerbose>1)cout<<"slope: "<<SlopeCurveFunction(NextPoint)<<endl;

   StepLength = 10;
   do{
      NextPoint = NextPoint + Direction*StepLength;
      i_loop++;
      if(fVerbose>1)cout<<"NextPoint: "<<NextPoint.X()<<" "<<NextPoint.Y()<<" "<<NextPoint.Z()<<endl;
   }while(LineFunction(NextPoint)&&i_loop<max_loop);//while(NextPoint.X()<100);
   NextPoint = NextPoint - Direction*StepLength;  //go back one step

   StepLength /=10;
   do{
      NextPoint = NextPoint + Direction*StepLength;
      i_loop++;
      if(fVerbose>1)cout<<"NextPoint: "<<NextPoint.X()<<" "<<NextPoint.Y()<<" "<<NextPoint.Z()<<endl;
   }while(LineFunction(NextPoint)&&i_loop<max_loop);//while(NextPoint.X()<100);
   NextPoint = NextPoint - Direction*StepLength;  //go back one step

   StepLength /=10;
   do{
      NextPoint = NextPoint + Direction*StepLength;
      i_loop++;
      if(fVerbose>1)cout<<"NextPoint: "<<NextPoint.X()<<" "<<NextPoint.Y()<<" "<<NextPoint.Z()<<endl;
   }while(LineFunction(NextPoint)&&i_loop<max_loop);//while(NextPoint.X()<100);
   NextPoint = NextPoint - Direction*StepLength;  //go back one step

   //calc pixel ID, use the distance of last point and (67.0518, -100.0000) , or (95.0000  -23.2129)
   Double_t distance_pixel = sqrt((NextPoint.X()-95)*(NextPoint.X()-95)+(NextPoint.Y()+23.2129)*(NextPoint.Y()+23.2129));

   i_FLG = i_phi;
   i_Pixel = Int_t(distance_pixel); //fixme
}


void PndGeoDskFLG::LineCylinderInteraction(TVector3 pos, TVector3 dir, TVector3 &pos_interaction)
{

  Double_t phi = dir.Phi();
  Double_t slope = tan(phi);
  Double_t A_xx = 1+slope*slope;
  Double_t B_x = 2*slope*(pos.Y()-pos.X()*slope);
  Double_t C_const = (pos.Y()-pos.X()*slope)*(pos.Y()-pos.X()*slope) - fRadius*fRadius;

  //cout<<"phi: "<<phi<<"  abc: "<<A_xx<<"  "<<B_x<<" "<<C_const<<endl;
  if((B_x*B_x-4*A_xx*C_const)<0){ cout<<" -E- PndGeoDskFLG::LineCylinderInteraction,  no solution? check it"<<endl; return;}
  double x_cylinder, y_cylinder, z_cylinder;
  if((phi>TMath::Pi()/2.&&phi<=TMath::Pi())||(phi>=-1*TMath::Pi()&&phi<-1*TMath::Pi()/2.)) {x_cylinder = (-1*B_x-sqrt(B_x*B_x-4*A_xx*C_const))/(2*A_xx); }
  else {x_cylinder = (-1*B_x+sqrt(B_x*B_x-4*A_xx*C_const))/(2*A_xx); }

  y_cylinder = x_cylinder*slope + (pos.Y()-pos.X()*slope);
  z_cylinder = sqrt((y_cylinder-pos.Y())*(y_cylinder-pos.Y()) + (x_cylinder-pos.X())*(x_cylinder-pos.X()))/tan(dir.Theta())+pos.Z();

  pos_interaction.SetXYZ(x_cylinder,y_cylinder,z_cylinder);

}

Bool_t PndGeoDskFLG::CurveFunction(TVector3 Point)
// to judge whether the input point (x1, y1, z2) exceed the curve function
{
Double_t x1 = Point.X();
Double_t y1 = Point.Y();

return (y1 < (a0 + a1*x1 + a2*x1*x1 + a3*x1*x1*x1 + a4*x1*x1*x1*x1 + a5*x1*x1*x1*x1*x1));
}

Bool_t PndGeoDskFLG::LineFunction(TVector3 Point)
{
Double_t x0 = 95.0000, y0 = -23.2129;
Double_t x1 = 67.0518, y1 = -100.0000;
Double_t x = Point.X();
Double_t y = Point.Y();

return (y > (y0 + (y1-y0)/(x1-x0)*(x-x0)));
}

Double_t PndGeoDskFLG::SlopeCurveFunction(TVector3 Point)
// to judge whether the input point (x1, y1, z2) exceed the curve function
{
Double_t x1 = Point.X();
//Double_t y1 = Point.Y(); //[R.K. 01/2017] unused variable?

return atan(a0*0. + a1 + 2*a2*x1 + 3*a3*x1*x1 + 4*a4*x1*x1*x1 + 5*a5*x1*x1*x1*x1);
}