CbmStsSimSensorDssdStereo.cxx

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/* Copyright (C) 2017-2020 GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt
   SPDX-License-Identifier: GPL-3.0-only
   Authors: Volker Friese [committer] */
 
#include "CbmStsSimSensorDssdStereo.h"
 
#include "CbmStsElement.h"
#include "CbmStsParSensorCond.h"
#include "CbmStsParSim.h"
#include "CbmStsPhysics.h"
 
#include <Logger.h>
 
#include <TGeoBBox.h>
#include <TGeoPhysicalNode.h>
#include <TMath.h>
 
 
using std::stringstream;
 
 
// -----   Constructor   ---------------------------------------------------
CbmStsSimSensorDssdStereo::CbmStsSimSensorDssdStereo(CbmStsElement* element) : CbmStsSimSensorDssd(element) {}
// -------------------------------------------------------------------------
 
 
// -----   Constructor   ---------------------------------------------------
CbmStsSimSensorDssdStereo::CbmStsSimSensorDssdStereo(Double_t dy, Int_t nStrips, Double_t pitch, Double_t stereoF,
                                                     Double_t stereoB, CbmStsElement* element)
  : CbmStsSimSensorDssd(element)
  , fNofStrips(nStrips)
  , fPitch(pitch)
  , fStereoF(stereoF)
  , fStereoB(stereoB)
  , fTanStereo()
  , fCosStereo()
  , fStripShift()
  , fErrorFac(0.)
{
  fDy = dy;
}
// -------------------------------------------------------------------------
 
 
// -----   Diffusion   -----------------------------------------------------
void CbmStsSimSensorDssdStereo::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);
 
  // x coordinate at the readout edge (y = fDy/2 )
  // This x is counted from the left edge.
  Double_t xRo = x + fDx / 2. - (fDy / 2. - y) * fTanStereo[side];
 
  // Centre strip number (w/o cross connection; may be negative or large than
  // the number of strips)
  Int_t iStrip = TMath::FloorNint(xRo / fPitch);
 
  // Strip boundaries at the readout edge (y = fDy/2)
  Double_t xLeftRo  = Double_t(iStrip) * fPitch;
  Double_t xRightRo = xLeftRo + fPitch;
 
  // Distance from strip boundaries across the strip
  Double_t dLeft  = (xRo - xLeftRo) * fCosStereo[side];
  Double_t dRight = (xRightRo - xRo) * fCosStereo[side];
 
  // 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;
}
// -------------------------------------------------------------------------
 
 
// -----   Get channel number in module   ----------------------------------
Int_t CbmStsSimSensorDssdStereo::GetModuleChannel(Int_t strip, Int_t side, Int_t sensorId) const
{
 
  // --- Check side argument
  assert(side == 0 || side == 1);
 
  // --- Account for offset due to stereo angle
  Int_t channel = strip - sensorId * fStripShift[side];
 
  // --- Account for horizontal cross-connection of strips
  while (channel < 0)
    channel += fNofStrips;
  while (channel >= fNofStrips)
    channel -= fNofStrips;
 
  // --- Account for front or back side
  if (side) channel += fNofStrips;
 
  return channel;
}
// -------------------------------------------------------------------------
 
 
// -----   Get strip number from coordinates   -----------------------------
Int_t CbmStsSimSensorDssdStereo::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) <= fDx / 2.);
  assert(TMath::Abs(y) <= fDy / 2.);
 
  // Calculate distance from lower left corner of the active area.
  // Note: the coordinates are given w.r.t. the centre of the volume.
  Double_t xdist = x + 0.5 * fDx;
  Double_t ydist = y + 0.5 * fDy;
 
  // Project coordinates to readout (top) edge
  Double_t xro = xdist - (fDy - ydist) * fTanStereo[side];
 
  // Calculate corresponding strip number
  Int_t iStrip = TMath::FloorNint(xro / fPitch);
 
  // Account for horizontal cross-connection of strips
  // not extending to the top edge
  while (iStrip < 0)
    iStrip += fNofStrips;
  while (iStrip >= fNofStrips)
    iStrip -= fNofStrips;
 
  return iStrip;
}
// -------------------------------------------------------------------------
 
 
// -----   Initialise   ----------------------------------------------------
Bool_t CbmStsSimSensorDssdStereo::Init()
{
 
  // Check presence of node
  assert(fElement);
  TGeoPhysicalNode* node = fElement->GetPnode();
  assert(node);
 
  // Check whether parameters are assigned
  assert(fNofStrips > 0);
 
  // Geometric shape of the sensor volume
  TGeoBBox* shape = dynamic_cast<TGeoBBox*>(node->GetShape());
  assert(shape);
 
  // Active size in x coordinate
  fDx = Double_t(fNofStrips) * fPitch;
  assert(fDx < 2. * shape->GetDX());
 
  // Active size in y coordinate
  assert(fDy < 2. * shape->GetDY());
 
  // Active size in z coordinate
  fDz = 2. * shape->GetDZ();
 
  // Stereo angle front side must be between -85 and 85 degrees
  assert(TMath::Abs(fStereoF) < 85.);
 
  // Stereo angle back side must be between -85 and 85 degrees
  assert(TMath::Abs(fStereoB) < 85.);
 
  // Derived variables
  fTanStereo[0]  = TMath::Tan(fStereoF * TMath::DegToRad());
  fCosStereo[0]  = TMath::Cos(fStereoF * TMath::DegToRad());
  fStripShift[0] = TMath::Nint(fDy * fTanStereo[0] / fPitch);
  fTanStereo[1]  = TMath::Tan(fStereoB * TMath::DegToRad());
  fCosStereo[1]  = TMath::Cos(fStereoB * TMath::DegToRad());
  fStripShift[1] = TMath::Nint(fDy * fTanStereo[1] / fPitch);
 
  // Set size of charge arrays
  fStripCharge[0].Set(fNofStrips);
  fStripCharge[1].Set(fNofStrips);
 
  // Factor for the hit position error
  fErrorFac = 1. / (fTanStereo[1] - fTanStereo[0]) / (fTanStereo[1] - fTanStereo[0]);
 
  // --- Flag parameters to be set if test is OK
  fIsSet = kTRUE;
 
  return fIsSet;
}
// -------------------------------------------------------------------------
 
 
// -----   Modify the strip pitch   ----------------------------------------
void CbmStsSimSensorDssdStereo::ModifyStripPitch(Double_t pitch)
{
 
  assert(fIsSet);  // Parameters should have been set before
 
  // Set new pitch and re-calculate number of strips
  fPitch     = pitch;
  fNofStrips = Int_t(fDx / pitch);
  fDx        = Double_t(fNofStrips) * pitch;
 
  // Set size of charge arrays
  fStripCharge[0].Set(fNofStrips);
  fStripCharge[1].Set(fNofStrips);
}
// -------------------------------------------------------------------------
 
 
// -----   Propagate charge to the readout strips   ------------------------
void CbmStsSimSensorDssdStereo::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;
 
  // Lorentz shift on the drift to the readout plane
  if (fSettings->LorentzShift()) { xCharge += LorentzShift(z, side, bY); }
 
  // 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)) { return; }
 
  // No diffusion: all charge is in one strip
  if (!fSettings->Diffusion()) {
    Int_t iStrip = GetStripNumber(xCharge, yCharge, side);
    fStripCharge[side][iStrip] += charge;
  }  //? 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.);
    // 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 = 0;                                       // left neighbour
    Int_t iStripR = 0;                                       // right neighbour
    if (fTanStereo[side] < 0.0001) {                         // vertical strips, no cross connection
      iStripL = iStripC - 1;                                 // might be = -1
      iStripR = iStripC + 1;                                 // might be = nOfStrips
    }
    else {  // stereo angle, cross connection
      iStripL = (iStripC == 0 ? fNofStrips - 1 : iStripC - 1);
      iStripR = (iStripC == fNofStrips - 1 ? 0 : iStripC + 1);
    }
    // Collect charge on the readout strips
    if (fracC > 0.) {
      fStripCharge[side][iStripC] += charge * fracC;  // centre strip
    }
    if (fracL > 0. && iStripL >= 0) {
      fStripCharge[side][iStripL] += charge * fracL;  // right neighbour
    }
    if (fracR > 0. && iStripR < fNofStrips) {
      fStripCharge[side][iStripR] += charge * fracR;  // left neighbour
    }
  }  //? Use diffusion
}
// -------------------------------------------------------------------------
 
 
// -----   String output   -------------------------------------------------
std::string CbmStsSimSensorDssdStereo::ToString() const
{
  stringstream ss;
  assert(fElement);
  ss << fElement->GetName() << " (DssdStereo): ";
  TGeoPhysicalNode* node = fElement->GetPnode();
  if (!node) ss << "no node assigned; ";
  else {
    TGeoBBox* shape = dynamic_cast<TGeoBBox*>(node->GetShape());
    assert(shape);
    ss << "Dimension (" << 2. * shape->GetDX() << ", " << 2. * shape->GetDY() << ", " << 2. * shape->GetDZ()
       << ") cm, ";
  }
  ss << "dy " << fDy << " cm, ";
  ss << "# strips " << fNofStrips << ", pitch " << fPitch << " cm, ";
  ss << "stereo " << fStereoF << "/" << fStereoB << " degrees";
  if (fConditions) ss << "\n\t Conditions: " << fConditions->ToString();
  return ss.str();
}
// -------------------------------------------------------------------------
 
 
ClassImp(CbmStsSimSensorDssdStereo)