[Gate-users] Change physics list/step function

[John Apostolakis]

Dear Jana,

If you are using any physics list with the ending _EMZ, then the electromagnetic processes is instantiated by the G4PhysicsFactory in the following line:

      } else if(4 == em_opt) {
p->ReplacePhysics(new G4EmStandardPhysics_option4(verbose));
     } …

The capability of GATE to create each process of a physics list via UI command uses different code, so you cannot mix and match between these options.

But after you define the physics list QGSP_BIC_EMZ,  it is possible to change the properties of the ionisation process, using the equivalent Geant4 UI command, which I believe is in one of the two directories:

   /process/eLoss
   /process/em

You may need to experiment with the order in which you place these UI commands.

Best regards,
John
===================================================
John Apostolakis,  EP Department, CERN
SFT (SoFTware for Experiments) Group
Office: Building 32/ room R-003 (ground floor),  Mail: J27210
Email:  john.apostolakis at cern.ch<mailto:john.apostolakis at cern.ch>       Office Tel:  +41-22-767-7239
------------------------------------------------------------------------------------------

I note that it is possible also to use C++ code (e.g. revised messengers or elsewhere)  to do this also:

   #include  “G4EmParameters.hh”
   ….
   G4EmParametters::SetStepFunction(G4double, G4double)


On 12 Dec 2019, at 14:33, Jana Kretschmer <jana.kretschmer at uni-oldenburg.de<mailto:jana.kretschmer at uni-oldenburg.de>> wrote:

Hi everyone,

I am facing a problem concerning the physics settings. I would like to use the physics list QGSP_BIC_EMZ but change the step function for electron ionisation (dRoverRange and finalRange). Is there anyone who has done this before or knows how I can do this in Gate?

I tried to do this via the commands:
/gate/physics/addPhysicsList         QGSP_BIC_EMZ
/gate/physics/processes/ElectronIonisation/setStepFunction e- 0.05 0.1 mm

Unfortunately this did not work, since my simulation output was:

eIoni:   for  e-    SubType= 2
      dE/dx and range tables from 100 eV  to 10 TeV in 220 bins
      Lambda tables from threshold to 10 TeV, 20 bins per decade, spline: 1
      finalRange(mm)= 0.01, dRoverRange= 0.2, integral: 1, fluct: 1, linLossLimit= 0.01
      ===== EM models for the G4Region  DefaultRegionForTheWorld ======
             PenIoni :  Emin=        0 eV    Emax=        1 MeV
        MollerBhabha :  Emin=        1 MeV   Emax=       10 TeV   deltaVI


I also tried to build my own physics list by adding all processes used in QGSP_BIC_EMZ and then setting the step function but I was not able to specify the physics models needed.

Best regards,
Jana

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