Message: Decay of stable particles!? Not Logged In (login)
 Next-in-Thread Next-in-Thread
 Next-in-Forum Next-in-Forum

Question Decay of stable particles!? 

Keywords: G4RadioactiveDecay
Forum: Particles
Date: 05 Jul, 2005
From: Sara Vecchio <sara.vecchio@pi.infn.it>

I would like to monitor the beta+ activity produced by shooting protons on a PMMA phantom (carbon, oxygen, hydrogen). I managed to produce only a very rough simulation (this is my first approach to GEANT4), with a cylindric phantom and vacuum around it, probably even the PhysicsList is not the proper one. I introduce the possibility of decay of the isotopes produced by proton-material interaction with the following code (made with "copy and paste" from the examples):

*****************************************************************

void PMMAtestPhysicsList::ConstructGeneral() {
  G4Decay* decayProcess = new G4Decay();
  theParticleIterator->reset();
  while( (*theParticleIterator)() ) {
	G4ParticleDefinition *particle = theParticleIterator->value();
	G4ProcessManager *pManager = particle->GetProcessManager();
	if(decayProcess->IsApplicable(*particle)) {
	  pManager->AddProcess(decayProcess);
	  pManager->SetProcessOrdering(decayProcess, idxPostStep);
	  pManager->SetProcessOrdering(decayProcess, idxAtRest);
	}
  }  

// Declare radioactive decay to the GenericIon in the IonTable.
  //
  const G4IonTable *theIonTable = G4ParticleTable::GetParticleTable()->GetIonTable();

  G4RadioactiveDecay*  theRadioactiveDecay = new G4RadioactiveDecay();
  for (G4int i=0; i<theIonTable->Entries(); i++)
    {
      G4String particleName = theIonTable->GetParticle(i)->GetParticleName();
      if (particleName == "GenericIon")
	{
	  G4ProcessManager* pmanager = theIonTable->GetParticle(i)->GetProcessManager();
	  pmanager->SetVerboseLevel(0);
	  pmanager ->AddProcess(theRadioactiveDecay);
	  pmanager ->SetProcessOrdering(theRadioactiveDecay, idxPostStep);
	  pmanager ->SetProcessOrdering(theRadioactiveDecay, idxAtRest);
	}
    } 
}
***************************************************

But when I run the simulation (250 MeV for protons hitting the material) I get the strange results that stable isotopes C12 or O16 seems to decay!! (and no C11 or O15 appears..)

I copy below some lines of what appears on my screen:

*****************************************************
G4Track Information: Particle = proton, Track ID = 1, Parent ID = 0
*********************************************************************
Step#    X(mm)    Y(mm)    Z(mm) KinE(MeV)  dE(MeV) StepLeng TrackLeng  NextVolume ProcName
    0     44.1     44.6      -50       250        0        0         0     expHall initStep
    6     46.3     48.7      192       149     20.3     33.3       242 PMMA_cyl_phys hLowEIoni
    7     46.5     49.1      198       142     4.06     6.45       248 PMMA_cyl_phys LElastic
**********************************************************************
G4Track Information: Particle = C12[0.0], Track ID = 4, Parent ID = 1
***********************************************************************
Step#    X(mm)    Y(mm)    Z(mm) KinE(MeV)  dE(MeV) StepLeng TrackLeng  NextVolume ProcName
    0     46.5     49.1      198      2.97        0        0         0 PMMA_cyl_phys initStep
    1     46.5     49.1      198      2.67      0.3 0.000261  0.000261 PMMA_cyl_phys hLowEIoni
   10     63.2     40.6      215         0        0        0   0.00363 PMMA_cyl_phys RadioactiveDecay
******************************************************

What's the mistake? Should I declare explicitly each isotope that I am interested to study? But why C12 and O16 seems to decay? And why there is no trace of their decay products?

Inline Depth:
 1 1
 All All
Outline Depth:
 1 1
 2 2
 All All
Add message: (add)

1 None: Re: Decay of stable particles!?   (Luciano - 05 Jul, 2005)
 Add Message Add Message
to: "Decay of stable particles!?"

 Subscribe Subscribe

This site runs SLAC HyperNews version 1.11-slac-98, derived from the original HyperNews


[ Geant 4 Home | Geant 4 HyperNews | Search | Request New Forum | Feedback ]