Impact Ionization: custom model (6ca646fb) · Commits · XRFLab109 / Allpix Squared

src/physics/ImpactIonization.hpp

+56 −0

Original line number	Diff line number	Diff line
		@@ -15,6 +15,8 @@
		#include <limits>
		#include <typeindex>

		#include <TFormula.h>

		#include "exceptions.h"

		#include "core/config/Configuration.hpp"
		@@ -222,6 +224,58 @@ namespace allpix {
		double hole_d_;
		};

		/**
		* @ingroup Models
		* @brief Custom mobility model for charge carriers
		*/
		class CustomGain : public ImpactIonizationModel {
		public:
		CustomGain(const Configuration& config, double threshold) : ImpactIonizationModel(threshold) {
		electron_gain_ = configure_gain(config, CarrierType::ELECTRON);
		hole_gain_ = configure_gain(config, CarrierType::HOLE);
		};

		double gain_factor(const CarrierType& type, double efield_mag) const override {
		if(type == CarrierType::ELECTRON) {
		return electron_gain_->Eval(efield_mag);
		} else {
		return hole_gain_->Eval(efield_mag);
		}
		};

		private:
		std::unique_ptr<TFormula> electron_gain_;
		std::unique_ptr<TFormula> hole_gain_;

		std::unique_ptr<TFormula> configure_gain(const Configuration& config, const CarrierType type) {
		std::string name = (type == CarrierType::ELECTRON ? "electrons" : "holes");
		auto function = config.get<std::string>("multiplication_function_" + name);
		auto parameters = config.getArray<double>("multiplication_parameters_" + name, {});

		auto gain = std::make_unique<TFormula>(("multiplication_" + name).c_str(), function.c_str());

		if(!gain->IsValid()) {
		throw InvalidValueError(config,
		"multiplication_function_" + name,
		"The provided model is not a valid ROOT::TFormula expression");
		}

		// Check if number of parameters match up
		if(static_cast<size_t>(gain->GetNpar()) != parameters.size()) {
		throw InvalidValueError(config,
		"multiplication_parameters_" + name,
		"The number of provided parameters and parameters in the function do not match");
		}

		// Set the parameters
		for(size_t n = 0; n < parameters.size(); ++n) {
		gain->SetParameter(static_cast<int>(n), parameters[n]);
		}

		return gain;
		};
		};

		/**
		* @brief Wrapper class and factory for impact ionization models.
		*
		@@ -258,6 +312,8 @@ namespace allpix {
		} else if(model == "none") {
		LOG(INFO) << "No impact ionization model chosen, charge multiplication not simulated";
		model_ = std::make_unique<NoImpactIonization>();
		} else if(model == "custom") {
		model_ = std::make_unique<CustomGain>(config, threshold);
		} else {
		throw InvalidModelError(model);
		}