CbmRadDamage.cxx

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#include "CbmRadDamage.h"
 
#include <FairLogger.h>  // for LOG
#include <TMath.h>       // for Exp, Qe, K
#include <TMathBase.h>   // for Abs
#include <TString.h>     // for TString, operator+, operator<<
 
#include <stdlib.h>  // for getenv
 
 
// =====   Constructor   ==================================================
CbmRadDamage::CbmRadDamage()
  : niel_neutron()
  , niel_proton()
  , niel_pion()
  , niel_electron()
  , fIAlpha(4.e-17)
  , fEGap0(1.166)
  , fEGapAlpha(4.73e-4)
  , fEGapBeta(636.)
  , fNeff0(9.0e11)
  , fNeffC(2.5e-14)
  , fNeffGc(1.5e-2)
  , fEpsilon(1.04e-12) {
  Init();
}
// ========================================================================
 
 
// =====   Destructor   ===================================================
CbmRadDamage::~CbmRadDamage() {}
// ========================================================================
 
 
// =====   Get leakage current   ==========================================
Double_t CbmRadDamage::GetLeakageCurrent(Double_t fluence,
                                         Double_t volume,
                                         Double_t temperature) {
 
  // --- Boltzmann constant in ev/K
  Double_t kB = TMath::K() / TMath::Qe();
 
  // --- Leakage current at room temperature (293 K)
  Double_t i20 = fIAlpha * fluence * volume;
 
  // --- Gap energy at given temperature
  Double_t eGap =
    fEGap0 - fEGapAlpha * temperature * temperature / (temperature + fEGapBeta);
 
  // --- Leakage current at given temperature
  Double_t exponent = -1. * eGap / 2. / kB * (1. / temperature - 1. / 293.);
  Double_t iLeak =
    i20 * temperature * temperature / 85849. * TMath::Exp(exponent);
 
  return iLeak;
}
// ========================================================================
 
 
// =====   Get NIEL factor   ==============================================
Double_t CbmRadDamage::GetNiel(Int_t type, Double_t energy) {
 
  // Convert energy to MeV like in table
  energy = energy * 1000.;
 
  std::map<Double_t, Double_t>* table = nullptr;
  Int_t atype                         = TMath::Abs(type);
 
  // Select table according to particle type
  switch (atype) {
    case 2112: table = &niel_neutron; break;  // neutrons
    case 2212: table = &niel_proton; break;   // protons
    case 211: table = &niel_pion; break;      // pions
    case 11: table = &niel_electron; break;   // electrons
    default: table = nullptr;
  }
 
  // Return zero for unknown particles
  if (!table) return 0.;
 
  // First table entry above selected energy
  std::map<Double_t, Double_t>::iterator it = table->upper_bound(energy);
 
  // Return zero if below lower limit
  if (it == table->begin()) {
    //LOG(warn) << "-I- Below table limit: " << atype << "  " << energy;
    return 0.;
  }
 
  // Return asymptotic value if above upper limit
  if (it == table->end()) {
    //LOG(warn) << "-I- Above table limit: " << atype << "  " << energy;
    switch (atype) {
      case 2112: return 0.44; break;
      case 2212: return 0.50; break;
      case 211: return 0.38; break;
      case 11: return 0.08; break;
      default: return 0.00; break;
    }
  }
 
  // Interpolate within table values
  Double_t e2 = (*it).first;
  Double_t v2 = (*it).second;
  it--;
  Double_t e1 = (*it).first;
  Double_t v1 = (*it).second;
 
  Double_t v = v1 + (v2 - v1) * (energy - e1) / (e2 - e1);
 
  return v;
}
// ========================================================================
 
 
// =====   Get full depletion voltage   ===================================
Double_t CbmRadDamage::GetVfd(Double_t fluence, Double_t d) {
 
  // --- Calculate effective doping concentration at given fluence
  Double_t corr1 = 0.7 * fNeff0 * (1. - TMath::Exp(-1. * fNeffC * fluence));
  Double_t corr2 = fNeffGc * fluence;
  Double_t nEff  = fNeff0 - corr1 - corr2;
 
  // --- Calculate full depletion voltage from doping concentration
  Double_t vfd = TMath::Qe() * nEff * d * d / 2. / fEpsilon;
 
  return vfd;
}
// ========================================================================
 
 
// =====   Private method Init   ==========================================
void CbmRadDamage::Init() {
 
  // --- Read NIEL tables
  ReadData("niel_neutrons.dat", niel_neutron);
  ReadData("niel_protons.dat", niel_proton);
  ReadData("niel_pions.dat", niel_pion);
  ReadData("niel_electrons.dat", niel_electron);
 
 
  // --- Proportionality constant of leakage current and fluence
  // --- for Silicon at room temperature
  // --- Numerical value provided by S. Chatterji
  fIAlpha = 4.e-17;  // [A/cm]
 
 
  // --- Constants for temperature dependence of leakage current
  // --- Values are for Silicon
  // --- Numerical values provided by S. Chatterji
  fEGap0     = 1.166;    // Gap energy [eV] at T = 0K
  fEGapAlpha = 4.73e-4;  // [ev/K]
  fEGapBeta  = 636.;     // [K]
 
 
  // --- Constants for effective doping concentration
  // --- Values are for Silicon
  // --- Numerical values provided by S. Chatterji
  fNeff0  = 9.0e11;   // Doping concentration without irradiation [cm^-3];
  fNeffC  = 2.5e-14;  // [cm^2]
  fNeffGc = 1.5e-2;   // [1/cm]
 
 
  // --- Permittivivity of Silicon
  fEpsilon = 1.04e-12;  // [F/cm]
}
// ========================================================================
 
 
// =====   Private method ReadData   ======================================
void CbmRadDamage::ReadData(const char* file,
                            std::map<Double_t, Double_t>& table) {
 
  TString wrkdir   = getenv("VMCWORKDIR");
  TString fileName = wrkdir + "/input/" + TString(file);
  LOG(info) << "Reading " << fileName;
 
  std::ifstream* data = new std::ifstream(fileName.Data());
  if (!data->is_open()) { LOG(fatal) << "Error when reading from file!"; }
 
  Double_t e     = 0.;
  Double_t v     = 0.;
  Int_t nEntries = 0;
 
  *data >> e >> v;
  while (!data->eof()) {
    table[e] = v;
    nEntries++;
    *data >> e >> v;
  }
 
  data->close();
  delete data;
 
  std::map<Double_t, Double_t>::iterator it1 = table.begin();
  std::map<Double_t, Double_t>::iterator it2 = table.end();
  it2--;
 
  LOG(info) << nEntries << " values read; energy range " << (*it1).first
            << " to " << (*it2).first << " MeV; map size " << table.size();
}
// ========================================================================
 
 
ClassImp(CbmRadDamage)