The abnormal energy deposit in the target

[siyuan1979]

The 10 MeV neutron was used to boom lithium 6 target with 3 inch height and 3 inch diameter, the energy deposit by the proton event by event is shown below:

the key codes are:

if (aStep->GetPreStepPoint()->GetTouchable()->GetVolume() == fTargetVolume)
 { 
     if(aStep->GetTrack()->GetDefinition()==G4Proton::ProtonDefinition()
        )
     {
         G4double energy_deposit = aStep->GetTotalEnergyDeposit();
         G4double step_length = aStep->GetStepLength() / 10.;
         // 发光效率系数为：1.903MeVee/MeV
         // Birks系数为：26.03g/cm2/MeV
         // ej-309的密度为：0.96g/cm3
         G4double fluorescence_energy = 1.903 * energy_deposit / (1 + 26.03 * 1.e-3 / 0.96 * energy_deposit / step_length);
         event_action_->Add_Energy(fluorescence_energy);
     }           
 }
Maybe the cross section of Li6(n,p) is wrong?

Geant4 Version:11.4.1
Operating System:Ubuntu 24.04
Compiler/Version:13.3.0
CMake Version:3.28.3

---

[maire1]

Here, a run of example Hadr03.

According to the printout, the cross section of Li6(n,p) is ~1.6% of 664 mbarn = 10.6 mbarn.

the proton spectrum is shown.

siyuan.mac.txt (386 Bytes)

siyuan.out.txt (4.7 KB)

[siyuan1979]

The proton energy from Li6(n,p) reaction is too high, it disagrees the energy conservation.

[dima51]

What is your electromagnetic physics module? It seems option3 and option4 have some problems, have you tried default option G4EmStandardPhysics()?

[siyuan1979]

The physics list “FTFP_BERT_HP” is used.

[dima51]

@siyuan1979

FTFP_BERT_HP

Then the electromagnetic physics is not the issue. FTFP_BERT_HP uses G4EmStandardPhysics.

[maire1]

Here, a “zoom” of Li6(n,p)He6 channel. All the 16087 events are in the peak Q= -5.449 MeV

Therefore (totEkin)out = proton + He6 = (totEkin)in + Q = 10 MeV - 5.449 MeV = 4.551 MeV

I do not see any energy violation in these events.

siyuan.mac.txt (426 Bytes)

[siyuan1979]

@maire1 , according your opinion, maybe something is wrong with my codes, but now the lithium 6 changed for hydrogen, and the total deposited energy is tallied, the result for hydrogen is:

this result seems right.

and the result for lithium 6 is:

why so much high energy deposited is tallied in one event?

[maire1]

Here, a run of example Hadr06, and the plot of total energy deposit for Hydrogen and Lithium6

siyuan.mac.txt (608 Bytes)

siyuan-Li.out.txt (21.9 KB)