BTLElectronicsSim.cc

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#include "SimFastTiming/FastTimingCommon/interface/BTLElectronicsSim.h"

#include "FWCore/MessageLogger/interface/MessageLogger.h"

#include "CLHEP/Random/RandPoissonQ.h"
#include "CLHEP/Random/RandGaussQ.h"


using namespace mtd;

BTLElectronicsSim::BTLElectronicsSim(const edm::ParameterSet& pset) :
  debug_( pset.getUntrackedParameter<bool>("debug",false) ),
  bxTime_(pset.getParameter<double>("bxTime") ),
  ScintillatorRiseTime_( pset.getParameter<double>("ScintillatorRiseTime") ),
  ScintillatorDecayTime_( pset.getParameter<double>("ScintillatorDecayTime") ),
  ChannelTimeOffset_( pset.getParameter<double>("ChannelTimeOffset") ),
  smearChannelTimeOffset_( pset.getParameter<double>("smearChannelTimeOffset") ),
  EnergyThreshold_( pset.getParameter<double>("EnergyThreshold") ),
  TimeThreshold1_( pset.getParameter<double>("TimeThreshold1") ),
  TimeThreshold2_( pset.getParameter<double>("TimeThreshold2") ),
  ReferencePulseNpe_( pset.getParameter<double>("ReferencePulseNpe") ),
  SinglePhotonTimeResolution_( pset.getParameter<double>("SinglePhotonTimeResolution") ),
  DarkCountRate_( pset.getParameter<double>("DarkCountRate") ),
  SigmaElectronicNoise_( pset.getParameter<double>("SigmaElectronicNoise") ),
  SigmaClock_( pset.getParameter<double>("SigmaClock")),
  Npe_to_pC_( pset.getParameter<double>("Npe_to_pC") ),
  Npe_to_V_( pset.getParameter<double>("Npe_to_V") ),
  adcNbits_( pset.getParameter<uint32_t>("adcNbits") ),
  tdcNbits_( pset.getParameter<uint32_t>("tdcNbits") ),
  adcSaturation_MIP_( pset.getParameter<double>("adcSaturation_MIP") ),
  adcBitSaturation_( std::pow(2,adcNbits_)-1 ),
  adcLSB_MIP_( adcSaturation_MIP_/adcBitSaturation_ ),
  adcThreshold_MIP_( pset.getParameter<double>("adcThreshold_MIP") ),
  toaLSB_ns_( pset.getParameter<double>("toaLSB_ns") ),
  tdcBitSaturation_( std::pow(2,tdcNbits_)-1 ),
  CorrCoeff_( pset.getParameter<double>("CorrelationCoefficient") ),
  cosPhi_( 0.5*(sqrt(1.+CorrCoeff_)+sqrt(1.-CorrCoeff_)) ),
  sinPhi_( 0.5*CorrCoeff_/cosPhi_ ),
  ScintillatorDecayTime2_(ScintillatorDecayTime_*ScintillatorDecayTime_),
  SPTR2_(SinglePhotonTimeResolution_*SinglePhotonTimeResolution_),
  DCRxRiseTime_(DarkCountRate_*ScintillatorRiseTime_),
  SigmaElectronicNoise2_(SigmaElectronicNoise_*SigmaElectronicNoise_),
  SigmaClock2_(SigmaClock_*SigmaClock_) { 
}


void BTLElectronicsSim::run(const mtd::MTDSimHitDataAccumulator& input,
                BTLDigiCollection& output,
                CLHEP::HepRandomEngine *hre) const {
  
  MTDSimHitData chargeColl, toa1, toa2;

  for(MTDSimHitDataAccumulator::const_iterator it=input.begin();
      it!=input.end();
      it++) {
    
    chargeColl.fill(0.f);
    toa1.fill(0.f);
    toa2.fill(0.f);
    for(size_t i=0; i<it->second.hit_info[0].size(); i++) {

      // --- Fluctuate the total number of photo-electrons
      float Npe = CLHEP::RandPoissonQ::shoot(hre, (it->second).hit_info[0][i]);
      if ( Npe < EnergyThreshold_ ) continue;


      // --- Get the time of arrival and add a channel time offset
      float finalToA1 = (it->second).hit_info[1][i] + ChannelTimeOffset_;
      
      if (  smearChannelTimeOffset_ > 0. ){
    float timeSmearing = CLHEP::RandGaussQ::shoot(hre, 0., smearChannelTimeOffset_);
    finalToA1 += timeSmearing;
      }


      // --- Calculate and add the time walk: the time of arrival is read in correspondence
      //                                      with two thresholds on the signal pulse
      std::array<float, 3> times = btlPulseShape_.timeAtThr(Npe/ReferencePulseNpe_,
                                TimeThreshold1_*Npe_to_V_, 
                                TimeThreshold2_*Npe_to_V_);


      // --- If the pulse amplitude is smaller than TimeThreshold2, the trigger does not fire
      if (times[1] == 0.) continue;

      float finalToA2 = finalToA1 + times[1];
      finalToA1 += times[0];


      // --- Uncertainty due to the fluctuations of the n-th photon arrival time:
      //     the fluctuations due to the first TimeThreshold1_ p.e. are common to both times
      float smearing_stat_thr1 = CLHEP::RandGaussQ::shoot(hre, 0., 
                 ScintillatorDecayTime_*sqrt(sigma2_pe(TimeThreshold1_,Npe)));
      float smearing_stat_thr2 = CLHEP::RandGaussQ::shoot(hre, 0.,
                     ScintillatorDecayTime_*sqrt(sigma2_pe(TimeThreshold2_-TimeThreshold1_,Npe)));
      finalToA1 += smearing_stat_thr1;
      finalToA2 += smearing_stat_thr1 + smearing_stat_thr2;


      // --- Add in quadrature the uncertainties due to the SiPM timing resolution, the SiPM DCR,
      //     the electronic noise and the clock distribution:
      float slew2 = ScintillatorDecayTime2_/Npe/Npe;

      float sigma2_tot_thr1 = SPTR2_/TimeThreshold1_ + (DCRxRiseTime_ + SigmaElectronicNoise2_)*slew2 + SigmaClock2_;
      float sigma2_tot_thr2 = SPTR2_/TimeThreshold2_ + (DCRxRiseTime_ + SigmaElectronicNoise2_)*slew2 + SigmaClock2_;


      // --- Smear the arrival times using the correlated uncertainties:
      float smearing_thr1_uncorr = CLHEP::RandGaussQ::shoot(hre, 0., sqrt(sigma2_tot_thr1));
      float smearing_thr2_uncorr = CLHEP::RandGaussQ::shoot(hre, 0., sqrt(sigma2_tot_thr2));

      finalToA1 += cosPhi_*smearing_thr1_uncorr + sinPhi_*smearing_thr2_uncorr;
      finalToA2 += sinPhi_*smearing_thr1_uncorr + cosPhi_*smearing_thr2_uncorr;


      // --- Fill the time and charge arrays
      const unsigned int ibucket = std::floor( finalToA1/bxTime_ );
      if ( (i+ibucket) >= chargeColl.size() ) continue;
      
      chargeColl[i+ibucket] += Npe*Npe_to_pC_; // the p.e. number is here converted to pC
      
      if ( toa1[i+ibucket] == 0. || (finalToA1-ibucket*bxTime_) < toa1[i+ibucket] ){
    toa1[i+ibucket] = finalToA1 - ibucket*bxTime_;
    toa2[i+ibucket] = finalToA2 - ibucket*bxTime_;
      }

    }

    //run the shaper to create a new data frame
    BTLDataFrame rawDataFrame( it->first );    
    runTrivialShaper(rawDataFrame,chargeColl,toa1,toa2);
    updateOutput(output,rawDataFrame);
    
  }
    
}

  
void BTLElectronicsSim::runTrivialShaper(BTLDataFrame &dataFrame, 
                     const mtd::MTDSimHitData& chargeColl,
                     const mtd::MTDSimHitData& toa1,
                     const mtd::MTDSimHitData& toa2) const {
    bool debug = debug_;
#ifdef EDM_ML_DEBUG  
  for(int it=0; it<(int)(chargeColl.size()); it++) debug |= (chargeColl[it]>adcThreshold_fC_);
#endif
    
  if(debug) edm::LogVerbatim("BTLElectronicsSim") << "[runTrivialShaper]" << std::endl;
  
  //set new ADCs 
  for(int it=0; it<(int)(chargeColl.size()); it++) {

    //brute force saturation, maybe could to better with an exponential like saturation
    const uint32_t adc = std::min( (uint32_t) std::floor(chargeColl[it]/adcLSB_MIP_), adcBitSaturation_ );
    const uint32_t tdc_time1 = std::min( (uint32_t) std::floor(toa1[it]/toaLSB_ns_), tdcBitSaturation_);
    const uint32_t tdc_time2 = std::min( (uint32_t) std::floor(toa2[it]/toaLSB_ns_), tdcBitSaturation_);

    BTLSample newSample;
    newSample.set(chargeColl[it] > adcThreshold_MIP_,false,tdc_time2,tdc_time1,adc);
    dataFrame.setSample(it,newSample);

    if(debug) edm::LogVerbatim("BTLElectronicsSim") << adc << " (" 
                            << chargeColl[it] << "/" 
                            << adcLSB_MIP_ << ") ";
  }

  if(debug) { 
    std::ostringstream msg;
    dataFrame.print(msg);
    edm::LogVerbatim("BTLElectronicsSim") << msg.str() << std::endl;
  } 
}
  
void BTLElectronicsSim::updateOutput(BTLDigiCollection &coll,
                     const BTLDataFrame& rawDataFrame) const {
  int itIdx(9);
  if(rawDataFrame.size()<=itIdx+2) return;
  
  BTLDataFrame dataFrame( rawDataFrame.id() );
  dataFrame.resize(dfSIZE);
  bool putInEvent(false);
  for(int it=0;it<dfSIZE; ++it) {    
    dataFrame.setSample(it, rawDataFrame[itIdx-2+it]);
    if(it==2) putInEvent = rawDataFrame[itIdx-2+it].threshold(); 
  }

  if(putInEvent) {
    coll.push_back(dataFrame);    
  }
}

float BTLElectronicsSim::sigma2_pe(const float& Q, const float& R) const {
  
  float OneOverR  = 1./R;
  float OneOverR2 = OneOverR*OneOverR;

  // --- This is Eq. (17) from Nucl. Instr. Meth. A 564 (2006) 185
  float sigma2 = Q * OneOverR2 * ( 1. + 2.*(Q+1.)*OneOverR + 
                   (Q+1.)*(6.*Q+11)*OneOverR2 +
                   (Q+1.)*(Q+2.)*(2.*Q+5.)*OneOverR2*OneOverR );

  return sigma2;

}