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Forum: Hadronic Processes
Re: Question Radioactive decay of tritium. (Antanas Bukartas)
Re: Idea Re: Radioactive decay of tritium. (Michael H. Kelsey)
Date: 17 Apr, 2016
From: Antanas Bukartas <Antanas Bukartas>

On Thu, 14 Apr 2016 21:09:53 GMT, Michael H. Kelsey wrote:
> On Thu, 14 Apr 2016 11:42:49 GMT, Antanas wrote:
> 
> > I am trying to model a liquid scintillation detector with a liquid
> > tritium source. For the modeling of the source i am using radioactive
> > decay libraries of Geant 10.02. I succeeded in implementing everything I
> > need to the OpNovice example. And it works for any other nuclei (for
> > example Carbon 14, Cobalt 60, etc..) except tritium. In the viewer I can
> > see a dot (generic ion) being created, but there is no secondary
> > particles. I tried setting the cuts with
> > // SetCutsWithDefault();
> >   G4ProductionCutsTable::GetProductionCutsTable()->SetEnergyRange(120*eV,
> > 1*GeV);
> > in the physics list, as the energy of tritium beta is 18.6 keV. But
> > still, no secondaries.
> 
> Unfortunately, the default behaviour in Geant4 is for tritium to be
> stable. You have to modify the physics associated with tritium "by hand"
> to have it decay. For SuperCDMS, I wrote a "TritiumPhysics" builder
> which I attach to whatever active physics list we are using:
> 
>   physList->RegisterPhysics(new CDMSTritiumPhysics);
> 
> where I define
> 
> void CDMSTritiumPhysics::ConstructProcess() {
>   // Make tritium unstable, so it can be decayed
>   G4ParticleDefinition* tr = G4Triton::Definition();
>   tr->SetPDGStable(false);
> 
>   // Remove G4Decay process, which requires a registered decay table
>   G4VProcess* decay = 0;
>   G4ProcessManager* pman = tr->GetProcessManager();
>   G4ProcessVector* pvec = pman->GetAtRestProcessVector();
>   for (G4int i=0; i<pvec->size() && decay==0; i++) {
>     if ((*pvec)[i]->GetProcessName() == "Decay") decay = (*pvec)[i];
>   }
>   if (decay) pman->RemoveProcess(decay);
> 
>   // Attach RDM, which is a rest-discrete process
>   tr->GetProcessManager()->AddProcess(new G4RadioactiveDecay(), 1000, -1, 1000);
> }
> 
> The middle part of this is needed because we don't have a built-in
> "G4Decay" table for tritium in Geant4, only the radioactive decay file.
> 
>   -- Michael Kelsey
> 

Thank you very much for a quick reply, but my system crashed and I had to reinstall everything. Took awhile... It seems, that after the injection of this code the radioactive decay of tritium works - the secondary electron of resembling energy is generated. Also other nuclides successfully decay. But this is only half of the puzzle. I have injected this code in to my main physics list's void OpNovicePhysicsList::ConstructProcess(), but now the scintillation processes does not work. I want to make a liquid mixture of the scintillator and tritium source. As I understand the scintillation processes are governed by the decay libraries, and we are turning them off? Is there a way to them both working?

Antanas.

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