Ambiguity with protons and alpha produced with higher energy than projectile neutron

Physics Processes, Models and Cross Sections
1

All_particles.txt (732.1 KB)

Dear Users and developers,

I am trying to simulate the 14.1 MeV Neutron-induced reaction on mustard gas (elemental composition C4H8Cl2S) of volume 50x25x25(LxWxH). The ambiguity appear in the production of Protons and Alpha particles with Kinetic energies more than 14.1 MeV ( second last column in attached file). I printed the information in the Stepping action for the following variables:
Event no. ParentID. TrackID. StepID. Particle Process volumeBeforeStep VolumeAfterStep K.E. Edep
.

Please see the attached file for the numbers. For this simulation, I used the following physics list :-

RegisterPhysics(new G4DecayPhysics());
RegisterPhysics(new G4EmStandardPhysics());
RegisterPhysics(new G4EmExtraPhysics());
RegisterPhysics(new G4HadronPhysicsQGSP_BERT_HP());
RegisterPhysics( new G4IonPhysics(2));
RegisterPhysics( new NeutronHPphysics());

based on ModularPhysicsList constructors. My doubt is how the secondaries can have more kinetic energies than the projectile. Furthermore, **why the deposition ( lets see event 265 in attached file) stopped at kinetic energy approximately to the projectile energy (~ 14 MeV).

Any suggestion and pointer will be highly appreciable. I hope, I am able to put the question in proper form.

With best regards,

2

Hello,

you are using HP neutron transport, in which there is no guarantee for 4-momentum balance on event-by-event basis, only in average. If for you this is important you may try out G4HadronPhysicsQGSP_BIC or G4HadronPhysicsQBBC. Also you register HP physics twice - difficult to predict how second constructor NeutronHPphysics will affect results.

VI

3

Dear Sir, Thank you for your reply and suggestions. It worked :slight_smile: . If I kept only G4HadronPhysicsQGSP_BIC physics model, there are no neturons/alphas/protons with kinetic energy more than 14. 1 MeV.
However, In the output file I can see the neturons and gammas with energy deposition ( event wise) more than the 14.1 MeV ( ~ 22 MeV). Can you please provide any pointer what can cause it. I have made my target sensitive ( mustard gas) and filling the ntupples (event-wise).

With best regards,

4

Hello,

it is possible to use UI command “/tracking/verbose 2”, which allow to show what energy is deposited at a step and what secondary particles are produced. Each concrete case may be discussed.

VI