Calculate secondary electrons

Physics Processes, Models and Cross Sections
1

Dear colleagues,

What physical list can be used to calculate secondary electrons for energies below 1keV?
where can i get less calculation error?

I’m testing this physics now:
G4EmPenelopePhysics
G4EmStandardPhysics_option4
G4EmDNAPhysics_option2

Best regards

2

DNA models are supposed to be the most accurate and they also have lowest energy limit of applicability for electrons (down to several eV). However, they can only be aplied to water. So from constructors that you’ve listed G4EmDNAPhysics_option2 is the answer if you operate with water phantom.

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4

thanks for your reply.

You are right, I operate with water phantoms.
But in water i create mixture at nanoparticle. In this case listed G4EmDNAPhysics_option2, I can be used ?

Best regards

5

No, if you make mixture water + another material (e.g. gold) then you can’t use G4EmDNAPhysics_option2. To use G4EmDNAPhysics_option2 you need to separate gold volume and water volume, e.g. you can model gold nanoparticle surrounded by pure water. Then you can use G4EmDNAPhysics_option2 for water and another constructor (e.g. G4EmStandardPhysics_option4) for gold. For information how to do it see “dnaphysics” and “microdosimetry” example (extended->medical->dna).

1 Like
6

Thanks,
I testing the physics of the ” dnaphysics “ example.
But, I can not start two physics (G4EmStandardPhysics_option4 and G4EmStandardPhysics_option4) in one PhysList at the same time…
Geant4 does not work with two physical libraries.
How can i do this? or something I do not understand it correctly?
image

7

I’m not sure what you were trying to do. You probably tried to register two different constructors to the same volume at the same time. You can read README file of “dnaphysics” example to understand what it does. You can also read User’s Guide For Application Developers to understand basics of using physical models in Geant4.

8

Hi Anatoly,

Can you include the macro file you are using when you get this error?

For this use case, you must register G4EmStandardPhysics_option4 and G4EmDNAPhysicsActivator in your PhysicsList. Then you register G4DNAPhysics_Option0 separately for a region in your macro file (you do not register the DNAPhysics_Option0 in the physics list, only in the macro file). Currently only G4DNAPhysics_Option0 can be registered at the same time as G4EmStandardPhysics_option4.

The output I see here looks like you have registered G4DNAPhysics_Option2 in your physics list and are then trying to activate G4EmStandardPhysics_option4 on top of it, which should not work.

Joseph

10

HI Joseph, thanks for your reply!

my macro file:
/run/verbose 1
/event/verbose 0
/tracking/verbose
/gun/particle gamma
/gun/energy 1.25 MeV
/run/beamOn 500000000

DNAPhysics_Option0 and G4EmStandardPhysics_option4 only can be registered at the same time.
I understand you correctly? and I can not use G4EmDNAPhysics_option2 ?
What is this physical library - G4DNAPhysics_Option0? I can not find information about…

my next steps:

  1. In the macro file add an entry:
    /process/em/AddDNARegion World DNA_Opt0
    So, All physical volumes that are located in the WORLD will be calculated this physics. This is true?
  2. My physList in this case:

PhysicsList::PhysicsList(): G4VModularPhysicsList()
{
defaultCutValue = 1.*nm;
SetVerboseLevel(1);

RegisterPhysics(new G4EmStandardPhysics_option4());
RegisterPhysics(new G4DecayPhysics());
RegisterPhysics(new G4RadioactiveDecayPhysics());
RegisterPhysics(new G4EmDNAPhysicsActivator());
}
PhysicsList::~PhysicsList()
{}
void PhysicsList::SetCuts()
{
SetCutsWithDefault();
}

best regards,
Anatoly Baulin

11

I tested this case. Why am I getting the following error ?

/process/em/AddDNARegion World DNA_Opt0
illegal application state — command refused:"/process/em/AddDNARegion World DNA_Opt0"

best regards,
Anatoly Baulin

12

Hi Anatoly,

The physics list you have shown me for cross-activation of DNA_Option0 and StandardPhysicsOption4 looks correct. Regarding your error, I believe this is happening because “/process/em/AddDNARegion World DNA_Opt0” needs to be invoked before the run manager is initialized. The run manager can either be initialized in your Geant4 program itself (typically in the main file through runManager->Initialize()) or in the macro through /run/initialize. You may have to comment out the line of code in your Geant4 program and instead call it in your macro. With a macro looking like:

/run/verbose 1
/event/verbose 0
/tracking/verbose
/process/em/AddDNARegion World DNA_Opt0
/run/initialize
/gun/particle gamma
/gun/energy 1.25 MeV
/run/beamOn 500000000

What you have said is correct only DNA_PhysicsOption0 can be registered with a standard physics model at the same time. You can not currently use Option2 in addition to other physics models.

All of the volumes located in world will be calculated with Option0 physics and when DNA physics are not applicable (usually when your particle has an energy greater than 1 MeV) the StandardPhysics_Option4 will be used.

Option0 refers to the initial version of Geant4DNA. Any publications prior to when the additional Geant4 DNA options became available will describe this physics model thoroughly.

Hope this is helpful,

Joseph

1 Like
13

Your information is very helpful to me!
Thanks again!

1 Like
14

Hello Joseph and Anatoly,

thank you very much for this discussion. The subject is far not trivial. We are still fixing issues in the activator. If activation of DNA Opt0 is working fine to you we will think about other DNA options.

Vladimir