Problem 2103

4.10.04.02

The project involves measuring x-rays produced by 160 keV electrons hitting a tungsten target.

The x-ray spectrum produced using the Penelope physics model had significantly higher peaks than the spectrum of x-rays produced using the Livermore physics model. The only difference in the source code was
RegisterPhysics(new G4EmPenelopePhysics());
versus
RegisterPhysics(new G4EmLivermorePhysics());
in the PhysicsList.cc file.

I added the line
output << step->GetTrack()->GetCreatorProcess()->GetProcessName() << '\n';
to the SteppingAction.cc file at the end of the part where the photon information is recorded.

The process names in the output with Livermore included eBrem and phot, where the x-rays with "phot" had energy close to the tungsten emission lines and the x-rays with "eBrem" had a much wider spectrum.

The process names in the output with Penelope included eBrem, eIoni, and phot. The x-rays with "phot" or "eIoni" had energy close to the tungsten emission lines and the x-rays with "eBrem" had a much wider spectrum.

When I removed the "eIoni" x-rays from the Penelope output, the spectrum of the remaining x-rays was not significantly different from the spectrum in the Livermore output.

I suspect a bug in the Livermore ionization model is preventing secondary photons from being added to the stack. G4PenelopeIonizationModel.cc includes source code that addresses atomic deexcitation. G4LivermoreIonizationModel.cc has the message "all old deexcitation code removed" but it does not say where the new deexcitation code is, so I can't compare the source codes.