SiPMTool.h

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/*
 * SiPMTool.h
 *
 *  Tool that adds cross-talk and noise from the SiPM and
 *  the efficiency function for detecting photons.
 *
 *  Created on 03 Mar 2020
 *      Author: Valerio Formato (based on code by Junjing Wang)
 */

#ifndef HERD_SIPMTOOL_H
#define HERD_SIPMTOOL_H

// HerdSoftware headers
#include "algorithms/digitization/FitDigitizationTools/FitMCDeposit.h"
#include "dataobjects/FitGeoParams.h"

// C++ headers
#include <map>
#include <random>

#include "algorithms/digitization/FitDigitizationTools/Units.h"

using poiss_param_t = std::poisson_distribution<unsigned int>::param_type;

// this in c++17 will become
// namespace Herd::FitDigitizationTools {
namespace Herd {
namespace FitDigitizationTools {

class SiPMTool {

public:
  void addNoise(int matID, FitMCDeposits &deposits);

  //===========================================================================
  // Return number of direct crosstalk PEs based on signal photons
  //===========================================================================
  int generateDirectXTalk(int nPhotons) {
    m_pois_dist.param(poiss_param_t{m_probDirectXTalk * nPhotons});
    return m_pois_dist(m_generator);
  }

  //===========================================================================
  // Return number of delayed crosstalk PEs based on signal photons
  //===========================================================================
  int generateDelayedXTalk(int nPhotons) {
    m_pois_dist.param(poiss_param_t{m_probDelayedXTalk * nPhotons});
    return m_pois_dist(m_generator);
  }

  //===========================================================================
  // Return (additional) time of delayed crosstalk
  //===========================================================================
  float generateDelayedXTalkTime() {
    // return -log(m_rndmFlat())*m_delayedXtalkDecayTime;
    // return -log(CLHEP::RandFlat::shoot()) * m_delayedXtalkDecayTime;
    return -log(m_flat_dist(m_generator)) * m_delayedXtalkDecayTime;
  }

  //===========================================================================
  // Return PDE for specific wavelength
  //===========================================================================
  float photonDetectionEfficiency(double wavelength);

  //===========================================================================
  // Return if SiPM is efficient for this wavelength
  //===========================================================================
  bool sipmDetectsPhoton(double wavelength);

  // N.B. this class doesn't own the geoParams. It just needs to read it, provided by the algorithms
  void SetGeoParams(const FitGeoParams *p_geoParams) {
    m_geoParams = p_geoParams;
    for (const auto &dcr : DCR_PE) {
      m_avgNumThermNoiseChans_PE[dcr.first] = m_geoParams->NChannelsPerMat() * dcr.second * sampling_time;
    }
  }

  // return weighted average of noise photoelectrons
  float GetAvgNumNoisePhotons();

private:
  void addThermalNoise(int matID, FitMCDeposits &depositCont);

  FitMCDeposits makeNoiseDeposits(const int noiseChannel, int matID, int nPhotons, double time);

  double m_probDirectXTalk = 0.04; // "Direct cross-talk probability per pe"};

  double m_probDelayedXTalk = 0.02; //"Delayed cross-talk probability per pe"};

  double m_delayedXtalkDecayTime = 14 * ns; //"Parameter for the exponential decay of the delayed X-talk"};

  // Parameters for the thermal noise simulation
  const FitGeoParams *m_geoParams;

  // from C. Perrina, private communication:
  // dark count rate for each noise photoelectron value:
  // 1 p.e. : 60 kHz @ 25C - 6.5V
  // 2 p.e. : 180 Hz @ 25C - 6.5V
  // 3 p.e. : 0.6 Hz @ 25C - 6.5V
  std::map<unsigned int, double> DCR_PE{{1, 60e3 / s}, {2, 180.0 / s}, {3, 0.6 / s}};
  double sampling_time = 300 * ns; // 300ns
  double timeOffset = 0 * ns;

  double p3 = 2.00479e-08;
  double p2 = -3.86277e-05;
  double p1 = 0.0234192;
  double p0 = -4.06522;

  // Number of noise deposits over total detector, in readout windows for each photoelectron value.
  std::map<unsigned int, float> m_avgNumThermNoiseChans_PE;

  std::mt19937 m_generator;
  std::uniform_real_distribution<double> m_flat_dist;
  std::poisson_distribution<unsigned int> m_pois_dist;
};
} // namespace FitDigitizationTools
} // namespace Herd
#endif // FTSIPMTOOL_H