RMGInnerBremsstrahlungProcess.hh

// Copyright (C) 2025 Zichen "Francis" Wang <https://orcid.org/0009-0007-4386-0819>
//
// This program is free software: you can redistribute it and/or modify it under
// the terms of the GNU Lesser General Public License as published by the Free
// Software Foundation, either version 3 of the License, or (at your option) any
// later version.
//
// This program is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
// FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more
// details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
#ifndef _RMG_INNER_BREMSSTRAHLUNG_PROCESS_HH
#define _RMG_INNER_BREMSSTRAHLUNG_PROCESS_HH
 
#include <memory>
#include <vector>
 
#include "G4GenericMessenger.hh"
#include "G4ParticleDefinition.hh"
#include "G4Positron.hh"
#include "G4Step.hh"
#include "G4Track.hh"
#include "G4VParticleChange.hh"
#include "G4WrapperProcess.hh"
#include "globals.hh"
 
class RMGInnerBremsstrahlungProcess : public G4WrapperProcess {
 
  public:

    explicit RMGInnerBremsstrahlungProcess(
        const G4String& aNamePrefix = "RMG_IB",
        G4ProcessType aType = fDecay
    );

    virtual ~RMGInnerBremsstrahlungProcess() = default;

    G4VParticleChange* AtRestDoIt(const G4Track& aTrack, const G4Step& aStep) override;

    G4VParticleChange* PostStepDoIt(const G4Track& aTrack, const G4Step& aStep) override;

    void SetEnabled(bool enabled) { fEnabled = enabled; }

    [[nodiscard]] bool IsEnabled() const { return fEnabled; }

    void SetBiasingFactor(double factor) { fBiasingFactor = factor; }

    [[nodiscard]] double GetBiasingFactor() const { return fBiasingFactor; }
 
  private:

    double PhiFunction(double W_prime, double omega);

    double ComputeIBSpectrum(
        double electron_energy,
        std::vector<double>& omegas,
        std::vector<double>& cdf
    );

    double SamplePhotonEnergy(const std::vector<double>& omegas, const std::vector<double>& cdf);

    void GenerateInnerBremsstrahlungForSecondaries(
        G4VParticleChange* particle_change,
        const G4Track& parent_track
    );

    bool IsBetaElectron(G4Track* track);
 
    // messenger stuff. Static so that only one messenger is registered at the shared command path,
    // regardless of how many per-isotope process instances are constructed.
    inline static std::unique_ptr<G4GenericMessenger> fMessenger = nullptr;
    void DefineCommands();
 
    inline static bool fEnabled = true;
    inline static double fBiasingFactor = 1.0;
};
 
#endif