Dear all,

I recently updated the Geant from version 10.7 to version 11.2 and found out quite a large difference in energy loss calculation between the two of them.

I use the same physics list in both versions (QGSP_BIC) in which the energy losses of ions are treated by means of G4ionIonisation. As I understand, by default it uses G4BraggIonModel and G4BetheBlochModel for different energy regions.

My test model consists of two layers, one made from titanium and other made from plutonium dioxide. The energy losses of 50Ti with starting energy of 280 MeV are collected in the way similar with example B4a - I get energy losses from each step from SteppingAction, accumulate them in EventAction and write in histogram.

Geant 10.7 gives a reasonable result for both layers - 7.9 MeV lost in titanium and 6.3 MeV lost in PuO2, which is close to other calculation methods I used (SRIM, range tables). But the version 11.2 for the same geometry with the same physic lists give losses 8.6 MeV and 28.0 MeV.

The G4AtimaEnergyLossModel gives the same result in both versions - 8.6 MeV in titanium and 8.6 MeV in PuO2.

The models for version 10.7 and version 11.2 are uploaded on Google Drive.

basic_models.zip - Google Drive

In the archive, basic_model_10 is the model for Geant 10.7 and basic_model_11 is the model for Geant 11.2.

What could be the reason for that? Are you able to reproduce these results?

Thank you!

Hello Dima,

Is it possible to repeat the test with Geant4 11.2.2 ?

VI

Yes, I got the same result in version 11.2.2. 8.6 MeV loss in titanium and 28.0 MeV loss in PuO2 using QGSP_BIC.