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Forum: Physics List
Re: Question low energy deuteron propagation (Abigail Bickley)
Date: 30 Oct, 2007
From: Vladimir IVANTCHENKO <vnivanch@mail.cern.ch>

On Tue, 30 Oct 2007, Abigail Bickley wrote:

> *** Discussion title: Physics List
> Email replies to PublicHyperNews@slac.stanford.edu must include:
>   In-Reply-To: <"/phys-list/424"@geant4-hn.slac.stanford.edu>
>   Subject: ...change this to be about your reply.
> 
> Dear Experts,
> 
> I am trying to simulate the propagation of a 300keV deuteron in a gas
> filled volume.  Simple range calculations tell me that the track length
> should be approximately 10cm.  However I find that in Geant the tracks
> are only ~2cm long.  Is geant capable of reproducing the interactions 
> of a deuteron of this energy in a gas?  I've included some specific 
> details below.  Suggestions would be appreciated.
> 
> Thank you for your advice,
> 
> Abby
>

Sorry, this Physics Lists is completely incorrect:

1) two processes of ionisation are included simulteneusly, ionisation is 
at least doubles.

2) standard and low-energy hadron ionisation cannot be used in the same 
Phsyics Lists

Would suggest to use Physics Lists from EM examples, for example:

$G4INSTALL/examples/extended/electromagnetic/TestEm7

VI


 
> Physics Processes in PhysicsList:
> pmanager->AddProcess(new G4MultipleScattering,-1, 1, 1);
> pmanager->AddProcess(new G4hIonisation,     -1, 2, 2);
> G4double demax = 0.05;  
> G4double stmin = 1.e-9 * m;
> G4hLowEnergyIonisation* lowEIonisation = new G4hLowEnergyIonisation();
> pmanager->AddProcess( lowEIonisation, -1,3,3);
> lowEIonisation->SetStepFunction( demax, stmin );
> *Is there a threshold cut being applied that is inappropriate?
> 
> Definition of gas in DetectorConstruction:
> //TPCgas_D2 is 100% D2
> G4Element* D = new G4Element("Deuterium","D", z= 2., a= 2.0141*g/mole);  
> G4Material* TPCgas_D2 = new G4Material("TPC_gas_D2",0.036*mg/cm3,1);  //0.2atm density
> TPCgas_D2->AddElement(D,2);
> *changing gas density has expected effect on particle path length;
> *since the particle is created in the gas volume it never interacts
> with any other material
> 
> Definition of deuteron in PrimaryEventGenerator:
> G4ParticleDefinition* particle = particleTable->FindParticle("deuteron");
> particleGun->SetParticleDefinition(particle);  
> energy = 0.3*MeV;
> p_z= G4UniformRand()*energy;
> p_x = G4UniformRand()*(energy-p_z);
> p_y = sqrt(energy*energy-p_x*p_x-p_z*p_z);
> particleGun->SetParticleEnergy(energy);
> particleGun->SetParticleMomentumDirection(G4ThreeVector(p_x,p_y,p_z));
> particleGun->GeneratePrimaryVertex(anEvent);
> *perhaps energy is per nucleon? (but doubling it doesn't solve the problem)
> *perhaps this is total energy not kinetic energy?
> 
> 

-- 
    Vladimir Ivanchenko  
    ### CERN PH SFT Tel: +41-22-76-78-871  Vladimir.Ivantchenko@cern.ch ###

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