Prompt‑γ disappear when I add optical physics in GATE 9.2 / Geant4 11.0

Physics Lists
1

Hi everyone,

Setup

  • GATE 9.2 (built against Geant4 11.0.0)
  • 180 MeV proton pencil beam along +Z
  • Water phantom: 8 × 8 × 40 cm³, centred at Z = 0 cm
  • Cherenkov detector (PbF₂ crystal + grease + SiPM) 10 cm downstream of the phantom
    → goal: Study prompt-γ that leave the water and enter the crystal

Physics macro (simplified)

# --- hadron + EMY list --------------------------------------------------------
/gate/physics/addPhysicsList  QGSP_BERT_HP_EMY    # works: I see prompt gamma

# ---  add optical + Cherenkov ------------------------------------------
/gate/physics/addPhysicsList  optical             # after this = 0 prompt γ
/gate/physics/addPhysicsList  scintillation
/gate/physics/addPhysicsList  cerenkov
With only the first line I get ≈ 5 × 10⁵ prompt gammas exiting the phantom
(as expected).

As soon as I add the three optical/scintillation/Cherenkov lines, the γ count
inside the phantom drops to zero.I tryied to write a macro and put everything in one macro but it was not helpful 

Question

I suspect that calling /gate/physics/addPhysicsList optical replaces
the earlier QGSP_BERT_HP_EMY list instead of adding to it, so all hadronic
interactions (and therefore prompt γ production) are turned off.

What is the correct way in GATE 9.2 to keep QGSP_BERT_HP_EMY but add
optical, scintillation and Cherenkov processes?


If a single combined physics list exists, which one do you recommend for
180 MeV proton prompt‑γ + optical transport?

Any pointer to an example macro or doc page would be greatly appreciated.

Thank you very much!
2

Did you check the GATE documentation? It doesn’t look obvious to me, but my guess is that you should be using the addProcess command, though I don’t know if that works with a physics builder like “optical.”

You may need to contact the GATE community for more help.

3

yes , I checked it and it is /gate/physics/addPhysicsList optical

4

This, at first pass, seems to be a gate issue. Mostly because of how strange this issue is:

It has been shown in recent Gate releases that activating the Cherenkov using in the physics list /gate/physics/addPhysicsList empenelope (or others) /gate/physics/addProcess Cerenkov is not enough to add the Cerenkov process in a Volume one needs to define an appropriate physics cut in the volume of interest, for the particule type of interest /gate/physics/Electron/SetCutInRegion Volume 0.1 mm in order to generate Cherenkov photon. The reason of the feature is still unclear.

From the bottom of the page @mkelsey linked. That seems suspicious. Does that issue persist if you activate just the optical and scintillation?

5

with this condition I do not have any optical photon or cherenkov in my simulation only prompt gamma
/gate/physics/addPhysicsList QGSP_BERT_HP_EMY
#/gate/physics/addPhysicsList optical
/gate/physics/addProcess optical
/gate/physics/addProcess Scintillation
#/gate/physics/addProcess Cerenkov e-
#/gate/physics/addProcess Cerenkov e+

I can not find any solution for this problem, neither when I activate this line #/gate/physics/addPhysicsList optical

6

Try updating to the latest version or at least 11.3.2.
This might be related and it was fixed in that version.

7

but I think the problem is not missing optical package, when I change the source from proton to gamma and directly shoot to crystal I have cherenkov and optical process