How to use the new version of the Penelope models

From version 9.2 of Geant4, the Penelope low-energy electromagnetic models for e^± and gamma-rays have been migrated to the new design (the same as for "Standard EM processes").

Notice: the new Penelope models are released as "beta" software. Deeper test and validation is ongoing. Feedback and comments from users are very welcome to improve the new code to production quality and to report for possible bugs.
The original Penelope processes are momentarily kept for backwards compatibility, but they will be removed in next Geant4 releases.
At the moment, the physics results by the original G4Penelope processes and the newly migrated models are exactly the same.

The model approach and the available Penelope models
How to use the new models in Geant4 user applications
Additional controls/settings for the models
How to access/retrieve physics information from the models

The model approach and the available Penelope models

In the old approach there were multiple versions of the same process, one in the standard EM package and one/two in the LowEnergy EM package (e.g. for Compton Scattering: G4LowEnergyCompton, G4PenelopeCompton and G4ComptonScattering).

In the new approach there is only one process (e.g. G4ComptonScattering) and multiple models that can be registered to the process (same approch as hadronic physics). For instance, the models available for the Compton scattering (to be registered to G4ComptonScattering) are: G4KleinNishinaCompton (default), G4PenelopeComponModel (Penelope) and G4LivermoreComptonModel (former LowEnergy model).

How to use the new models in Geant4 user applications

The following code can be used in the physics list, to register the Penelope models to the EM processes:
first instantiate the process and then register the model to the process.

  #include "G4PenelopeComptonModel.hh";
  #include "G4ComptonScattering.hh";
  G4ComptonScattering* theComptonScattering = new G4ComptonScattering();
  theComptonScattering->SetModel(new G4PenelopeComptonModel());
  pmanager->AddDiscreteProcess(theComptonScattering);

  #include "G4PenelopeIonisationModel.hh";
  #include "G4eIonisation.hh";
  G4eIonisation* theIonisation = new G4eIonisation();
  theIonisation->SetModelEm(new G4PenelopeIonisationModel());
  pmanager->AddProcess(theIonisation,-1,1,1);

Notice: for discrete processes (Compton and Rayleigh scattering, pair production, photo-electric effect and positron annihilation), the method to invoke is SetModel()
For continuous-discrete processes (bremsstrahlung and ionisation), the method is SetEmModel().

The processes to which the Penelope models have to be registered are summarized in the table below:

Additional controls/settings for the models
All Penelope models have a method called SetVerbosityLevel() to set the verbosity level (default verbosity is 0).
The verbosity scales goes from 0 to 4:
  0 = no verbosity
  1 = warning for energy non-conservation
  2 = details of energy budget
  3 = calculation of cross sections/stopping powers, file openings, sampling of atoms
  4 = entering in methods

Penelope models which are interfaced to the G4AtomicDeexcitation (ionisation, Compton and photo-electric) have a method called SetUseAtomicDeexcitation() to switch on/off the fluorescence production. Default is true, namely fluorescence is explicitely produced. If it set to false, the energy for fluorescence products is deposited locally.

How to access/retrieve physics information from the models
The new model approach makes the physics content more transparent to users. It also makes possible to use all general tools (e.g. G4EmCalculator) that are available for the "Standard" electromagnetic models. For instance, this is the code to retrieve directly from the model the mean free path and the stopping power from G4PenelopeIonisationModel for electrons in a given material.
The code below gives: (1) the ionisation mean free path in the material aMaterial for production of delta rays above energy=energyCut for electrons of energy initEnergy; (2) the stopping power due to soft ionisation (below energyCut).

  #include "G4PenelopeIonisationModel.hh"
  #include "G4Electron.hh"
  G4PenelopeIonisationModel* ioni = new G4PenelopeIonisationModel();
  G4DataVector dummy;
  ioni->Initialise(G4Electron::Definition(),dummy); //initialise the model
  ioni->SetVerbosityLevel(1); //optional verbosity level
  //
  G4double inverseMFP = ioni->CrossSectionPerVolume(aMaterial,
                      G4Electron::Definition(), initEnergy,energyCut);
  G4cout << "Mean free path in " << aMaterial->GetName() <<
     " at " << initEnergy/keV <<
      " keV for energy > " << energyCut/keV << " keV = " <<
      (1./inverseMFP)/mm << " mm" << G4endl;
  //
  G4double sPower = ioni->ComputeDEDXPerVolume(aMaterial,
                      G4Electron::Definition(), initEnergy,energyCut);
  G4cout << "Stopping power path in " << aMaterial->GetName() <<
     " at " << initEnergy/keV <<
      " keV for energy < " << energyCut/keV << " keV = " <<
      sPower/(keV/mm) << "keV/mm" << G4endl;
  //

For more examples, see also the extended example electromagnetic/TestEm0