algorithms/digi/LGADPulseGeneration.h

0001 // SPDX-License-Identifier: LGPL-3.0-or-later
0002 // Copyright (C) 2024 Souvik Paul, Chun Yuen Tsang, Prithwish Tribedy
0003 // Special Acknowledgement: Kolja Kauder
0004 //
0005 // Convert energy deposition into ADC pulses
0006 // ADC pulses are assumed to follow the shape of landau function
0007
0008 #pragma once
0009
0010 #include <DDRec/CellIDPositionConverter.h>
0011 #include <RtypesCore.h>
0012 #include <TMath.h>
0013 #include <algorithms/algorithm.h>
0014 #include <edm4hep/RawTimeSeriesCollection.h>
0015 #include <edm4hep/SimTrackerHitCollection.h>
0016 #include <memory>
0017 #include <string>
0018 #include <string_view>
0019 #include <unordered_map>
0020 #include <vector>
0021
0022 #include "algorithms/digi/LGADPulseGenerationConfig.h"
0023 #include "algorithms/interfaces/WithPodConfig.h"
0024
0025 namespace eicrecon {
0026
0027 using LGADPulseGenerationAlgorithm =
0028     algorithms::Algorithm<algorithms::Input<edm4hep::SimTrackerHitCollection>,
0029                           algorithms::Output<edm4hep::RawTimeSeriesCollection>>;
0030
0031 class LGADPulseGeneration : public LGADPulseGenerationAlgorithm,
0032                             public WithPodConfig<LGADPulseGenerationConfig> {
0033 // The key pair is <NO of 40 MHz cycle since t = 0, cellID>
0034 typedef std::unordered_map<dd4hep::rec::CellID, std::unordered_map<int, std::vector<double>>> AdcArray;
0035
0036 public:
0037   LGADPulseGeneration(std::string_view name)
0038       : LGADPulseGenerationAlgorithm{name, {"RawHits"}, {"OutputPulses"}, {}} {}
0039   virtual void init() final;
0040   void process(const Input&, const Output&) const final;
0041
0042 private:
0043   class PulseShape {
0044   public:
0045     // return voltage in units of ADC value
0046     // ranges from 0 to adc_range
0047     // charge is in unit GeV, it's the EDep in the detector
0048     virtual double Eval(double time, double hit_time, double charge) = 0;
0049     virtual ~PulseShape() {};
0050   };
0051
0052   // default pulse shape is Landau
0053   class LandauPulse : public PulseShape {
0054   public:
0055     LandauPulse(double gain, double Vm, double sigma_analog, double adc_range) {
0056       m_gain = gain;
0057       m_sigma_analog = sigma_analog;
0058
0059       // calculation of the extreme values for Landau distribution can be found on lin 514-520 of
0060       // https://root.cern.ch/root/html524/src/TMath.cxx.html#fsokrB Landau reaches minimum for mpv =
0061       // 0 and sigma = 1 at x = -0.22278
0062       const double x_when_landau_min = -0.22278;
0063       const double landau_min    = -gain * TMath::Landau(x_when_landau_min, 0, 1, kTRUE) / m_sigma_analog;
0064       m_scalingFactor = 1. / Vm / landau_min * adc_range;
0065     }
0066     double Eval(double time, double hit_time, double charge) {
0067       return charge * m_gain * TMath::Landau(time, hit_time, m_sigma_analog, kTRUE) * m_scalingFactor;
0068     }
0069   private:
0070     double m_gain;
0071     double m_sigma_analog;
0072     double m_scalingFactor;
0073   };
0074
0075   double _Landau(double amp, double x, double mean, double std) const;
0076   void _FillADCArray(AdcArray& adc_sum, double charge, double mpv_analog,
0077                   int n_EICROC_cycle, dd4hep::rec::CellID cellID) const;
0078   std::unique_ptr<PulseShape> m_pulse;
0079 };
0080
0081 } // namespace eicrecon