CbmStsSensorDssdOrtho.cxx

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#include "CbmStsSensorDssdOrtho.h"
 
#include <cassert>
 
#include "TGeoBBox.h"
#include "TMath.h"
 
#include "CbmStsDigitizeParameters.h"
#include "CbmStsPhysics.h"
#include "CbmStsSetup.h"
 
 
using namespace std;
 
 
// -----   Constructor   ---------------------------------------------------
CbmStsSensorDssdOrtho::CbmStsSensorDssdOrtho(UInt_t address,
                                             TGeoPhysicalNode* node,
                                             CbmStsElement* mother) :
             CbmStsSensorDssd(address, node, mother),
             fNofStrips(), fPitch()
{
}
// -------------------------------------------------------------------------
 
 
 
// -----   Diffusion   -----------------------------------------------------
void CbmStsSensorDssdOrtho::Diffusion(Double_t x, Double_t y,
                                      Double_t sigma, Int_t side,
                                      Double_t& fracL, Double_t& fracC,
                                      Double_t& fracR) {
 
  // Check side qualifier
  assert( side == 0 || side == 1);
 
  // Coordinate at the readout edge (y = fDy/2 ).
  // This x is counted from the left / bottom corner.
  Double_t aRo = (side == 0 ? x + fDx / 2. : y + fDy / 2.);
 
  // Centre strip number
  Int_t iStrip = TMath::FloorNint(aRo / fPitch[side]);
 
  // Strip boundaries at the readout edge
  Double_t aLeftRo  = Double_t(iStrip) * fPitch[side];
  Double_t aRightRo = aLeftRo + fPitch[side];
 
  // Distance from strip boundaries across the strip
  Double_t dLeft  = aRo - aLeftRo;
  Double_t dRight = aRightRo - aRo;
 
  // Charge fractions
  // The value 0.707107 is 1/sqrt(2)
  fracL = 0.;
  if ( dLeft < 3. * sigma )
    fracL = 0.5 * ( 1. - TMath::Erf( 0.707107 * dLeft  / sigma) );
  fracR = 0.;
  if ( dRight < 3. * sigma )
    fracR = 0.5 * ( 1. - TMath::Erf( 0.707107 * dRight / sigma) );
  fracC = 1. - fracL - fracR;
 
  LOG(debug4) << GetName() << ": Distances to next strip " << dLeft << " / "
      << dRight << ", charge fractions " << fracL << " / " << fracC
      << " / " << fracR;
}
// -------------------------------------------------------------------------
 
 
 
// -----   Get channel number in module   ----------------------------------
Int_t CbmStsSensorDssdOrtho::GetModuleChannel(Int_t strip, Int_t side,
                                              Int_t sensorId) const {
 
  // --- Check side and sensor ID
  assert( side == 0 || side == 1);
  assert( sensorId == 0);
 
  // --- Account for front or back side
  Int_t channel = strip;
  if ( side ) channel += fNofStrips[0];
 
  return channel;
}
// -------------------------------------------------------------------------
 
 
 
// -----   Get strip number from coordinates   -----------------------------
Int_t CbmStsSensorDssdOrtho::GetStripNumber(Double_t x, Double_t y,
                                            Int_t side) const {
 
  // Cave: This implementation assumes that the centre of the sensor volume
  // is also the centre of the active area, i.e. that the inactive borders
  // (guard ring) are symmetric both and x and y (not necessarily the same
  // in x and y).
 
  // Check side
  assert( side == 0 || side == 1);
 
  // Check whether in active area (should have been caught before)
  assert ( TMath::Abs(x) < 0.5 * fDx );
  assert ( TMath::Abs(y) < 0.5 * fDy );
 
  // Calculate distance from lower left corner of the active area,
  // in x for the front side, in y for the back side.
  // Note: the coordinates are given w.r.t. the centre of the volume.
  Double_t dist = ( side == 0 ? x + 0.5 * fDx : y + 0.5 * fDy);
 
  // Calculate corresponding strip number
  Int_t iStrip = TMath::FloorNint( dist / fPitch[side] );
 
  return iStrip;
}
// -------------------------------------------------------------------------
 
 
 
// -----   Modify the strip pitch   ----------------------------------------
void CbmStsSensorDssdOrtho::ModifyStripPitch(Double_t pitch) {
 
  assert(fIsSet);  // Parameters should have been set before
 
  // Set new pitch and re-calculate number of strips on both sides
  fPitch[0] = pitch;
  fNofStrips[0] = Int_t( fDx / pitch );
  fDx = Double_t(fNofStrips[0]) * pitch;
  fPitch[1] = pitch;
  fNofStrips[1] = Int_t( fDy / pitch );
  fDy = Double_t(fNofStrips[1]) * pitch;
 
  // Set size of charge arrays
  fStripCharge[0].Set(fNofStrips[0]);
  fStripCharge[1].Set(fNofStrips[1]);
 
}
// -------------------------------------------------------------------------
 
 
 
// -----   Propagate charge to the readout strips   ------------------------
void CbmStsSensorDssdOrtho::PropagateCharge(Double_t x, Double_t y,
                                            Double_t z, Double_t charge,
                                            Double_t bY, Int_t side) {
 
  // Check side qualifier
  assert( side == 0 || side == 1);
 
  Double_t xCharge = x;
  Double_t yCharge = y;
  Double_t zCharge = z;
 
  // Debug
  LOG(debug4) << GetName() << ": Propagating charge " << charge
      << " from (" << x << ", " << y << ", " << z
      << ") on side " << side << " of sensor " << GetName()
     ;
 
  // Lorentz shift on the drift to the readout plane
  if ( CbmStsSetup::Instance()->GetDigiParameters()->GetUseLorentzShift() ) {
    xCharge += LorentzShift(z, side, bY);
  }
  LOG(debug4) << GetName() << ": After Lorentz shift: (" << xCharge << ", "
      << yCharge << ", " << zCharge << ") cm";
 
  // Stop if the charge after Lorentz shift is not in the active area.
  // Diffusion into the active area is not treated.
  if ( ! IsInside(xCharge, yCharge) ) {
    LOG(debug4) << GetName() << ": Charge outside active area"
       ;
    return;
  }
 
  // No diffusion: all charge is in one strip
  if ( ! CbmStsSetup::Instance()->GetDigiParameters()->GetUseDiffusion() ) {
    Int_t iStrip = GetStripNumber(xCharge, yCharge, side);
    fStripCharge[side][iStrip] += charge;
    LOG(debug4) << GetName() << ": Adding charge " << charge << " to strip "
        << iStrip;
  } //? Do not use diffusion
 
  // Diffusion: charge is distributed over centre strip and neighbours
  else {
    // Calculate diffusion width
    Double_t diffusionWidth =
        CbmStsPhysics::DiffusionWidth(z + fDz / 2.,  // distance from back side
                                      fDz,
                                      GetConditions()->GetVbias(),
                                      GetConditions()->GetVfd(),
                                      GetConditions()->GetTemperature(),
                                      side);
    assert (diffusionWidth >= 0.);
    LOG(debug4) << GetName() << ": Diffusion width = " << diffusionWidth
        << " cm";
    // Calculate charge fractions in strips
    Double_t fracL = 0.;  // fraction of charge in left neighbour
    Double_t fracC = 1.;  // fraction of charge in centre strip
    Double_t fracR = 0.;  // fraction of charge in right neighbour
    Diffusion(xCharge, yCharge, diffusionWidth, side, fracL, fracC, fracR);
    // Calculate strip numbers
    // Note: In this implementation, charge can diffuse out of the sensitive
    // area only for vertical strips. In case of stereo angle (cross-connection
    // of strips), all charge is assigned to some strip, so the edge effects
    // are not treated optimally.
    Int_t iStripC  = GetStripNumber(xCharge, yCharge, side);  // centre strip
    Int_t iStripL  = iStripC - 1;                             // left neighbour
    Int_t iStripR  = iStripC + 1;                             // right neighbour
    // Collect charge on the readout strips
    if ( fracC > 0. ) {
      fStripCharge[side][iStripC] += charge * fracC;    // centre strip
      LOG(debug4) << GetName() << ": Adding charge " << charge * fracC
          << " to strip " << iStripC;
    }
    if ( fracL > 0. && iStripL >= 0 ) {
      fStripCharge[side][iStripL] += charge * fracL;  // right neighbour
      LOG(debug4) << GetName() << ": Adding charge " << charge * fracL
          << " to strip " << iStripL;
    }
    if ( fracR > 0. && iStripR < fNofStrips[side] ) {
      fStripCharge[side][iStripR] += charge * fracR;  // left neighbour
      LOG(debug4) << GetName() << ": Adding charge " << charge * fracR
          << " to strip " << iStripR;
    }
  } //? Use diffusion
 
}
// -------------------------------------------------------------------------
 
 
 
// -----   Set internal sensor parameters   --------------------------------
Bool_t CbmStsSensorDssdOrtho::SetParameters(Int_t nStripsF, Double_t pitchF,
                                            Int_t nStripsB, Double_t pitchB) {
 
  // Geometric shape of the sensor volume
  TGeoBBox* shape = dynamic_cast<TGeoBBox*>(GetPnode()->GetShape());
 
  // Active size in x coordinate
  fDx = Double_t(nStripsF) * pitchF;
  assert( fDx < 2. * shape->GetDX() );  // The strips fit into the volume
 
  // Active size in y coordinate
  fDy = Double_t(nStripsB) * pitchB;
  assert( fDy < 2. * shape->GetDY() );
 
  // Active size in z coordinate
  fDz = 2. * shape->GetDZ();
 
  // Number of strips, pitch and stereo angles
  fNofStrips[0] = nStripsF;
  fPitch[0]     = pitchF;
  fNofStrips[1] = nStripsB;
  fPitch[1]     = pitchB;
 
  // Set size of charge arrays
  fStripCharge[0].Set(fNofStrips[0]);
  fStripCharge[1].Set(fNofStrips[1]);
 
  // Daisy chains are not allowed. Make sure that this is the only sensor
  // connected to the module.
  assert ( GetSensorId() == 0);
 
  // --- Flag parameters to be set if test is ok
  fIsSet = SelfTest();
 
  return fIsSet;
}
// -------------------------------------------------------------------------
 
 
 
// -----   String output   -------------------------------------------------
string CbmStsSensorDssdOrtho::ToString() const
{
  stringstream ss;
  ss << "Sensor " << fName << "(type " << GetTitle() << "): ";
  if ( ! fIsSet ) {
    ss << "parameters are not set";
    return ss.str();
  }
  ss << "Dimension (" << fDx << ", " << fDy << ", " << fDz << ") cm, ";
  ss << "# strips " << fNofStrips[0] << "/" << fNofStrips[1] << ", ";
  ss << "pitch " << fPitch[0] << "/" << fPitch[1] << " cm, ";
  return ss.str();
}
// -------------------------------------------------------------------------