Can't find metastable 99mTc

[imelnyk]

Hello dear Geant4 experts,

I write a simulation of 100Mo(p, x)Y, particularly 100Mo(p, 2n)99mTc nuclear reaction on a cyclotron solid target. But there is a problem: Geant4 does not see this isomeric state of 99Tc, it gives me only the ground state 99Tc with half-life of 9.61096e+21 sec, which probably indicates the stability of the nucleus. However, I need exactly the metastable 99mTc. I tried to use:
G4IonTable::GetIonTable()->GetIon(43, 99, 0, G4Ions::G4FloatLevelBase::plus_X), but it didn’t help, the produced isotope is still in ground state.

What would you suggest me to do in order to find the 99mTc?

Many thanks,
Ihor

[jrellin]

What physics lists are you using? I imagine that the Activation example will be extremely helpful here.

[imelnyk]

@jrellin
Currently, I use G4HadronPhysicsQGSP_BERT and also radioactive decay; I also tried all commented options, for instance for G4HadronPhysicsQGSP_BIC no 99Tc was produced, only 100Tc

The constructor of physics list is:

MolybdenumPhysicsListGeneral::MolybdenumPhysicsListGeneral() : G4VModularPhysicsList() {
    G4PhysListUtil::InitialiseParameters();
    G4NuclideTable::GetInstance()->SetMeanLifeThreshold(1 * CLHEP::picosecond);
    G4NuclideTable::GetInstance()->SetLevelTolerance(1.0 * CLHEP::eV);
    G4LossTableManager::Instance();
    G4DeexPrecoParameters* deex = G4NuclearLevelData::GetInstance()->GetParameters();
    deex->SetCorrelatedGamma(false);
    deex->SetStoreAllLevels(true);
    deex->SetIsomerProduction(true);
    // deex->SetInternalConversionFlag(true);
    deex->SetDiscreteExcitationFlag(true);
    deex->SetMaxLifeTime(1 * CLHEP::picosecond);

    // electromagnetic physics
    RegisterPhysics(new G4EmStandardPhysics_option3(1));


    // RegisterPhysics(new G4HadronPhysicsQGSP_BIC(1));
    // hadron inelastic physics
    RegisterPhysics(new G4HadronPhysicsQGSP_BERT(1));
    // RegisterPhysics(new G4HadronPhysicsFTFP_BERT_HP());
    // RegisterPhysics(new G4HadronPhysicsQGSP_BIC_AllHP());
    // RegisterPhysics(new G4HadronInelasticQBBC_ABLA(1));

    // // hadron elastic physics
    // RegisterPhysics(new G4HadronElasticPhysicsHP(1));
    //
    // // ion elastic physics
    // RegisterPhysics(new G4IonElasticPhysics(1));
    //
    //
    // // ion inelastic physics
    // RegisterPhysics(new G4IonPhysicsXS(1));
    //
    //
    // // stopping physics
    // RegisterPhysics(new G4StoppingPhysics(1));


    // gamma-nuclear physics
    // RegisterPhysics(new GammaNuclearPhysics("gamma"));


    // decay physics
    RegisterPhysics(new G4DecayPhysics(1));


    // radioactive decay physics
    RegisterPhysics(new G4RadioactiveDecayPhysics(1));


    // EM physics list
    // electromagnetic_physics_list_ = new G4EmStandardPhysics_option3(1);
    // hadron_physics_list_          = new G4HadronPhysicsQGSP_BIC_AllHP(1);
}

[maire1]

Here, a macro for example Hadr03 and its printout.
In PhysicsList.cc, I used G4HadronPhysicsQGSP_BIC

You can see that 2376 Tc99 [142.684] are produced, for 10000 inelastic collisions
imelnyk.mac.txt (260 Bytes)
imelnyk.out.txt (4.2 KB)

with example rdecay01, you can check that Tc99 [142.684] is metastable
Tc99m.mac.txt (286 Bytes)

[imelnyk]

@maire1 Thanks a lot ! I will try and report the results

[imelnyk]

@maire1 and others, thanks for the advice, I managed to produce 99mTc nucleus following a similar approach as Hadr03 example suggest, but there is an enormous life time retrieved from PDG data. I use:
const G4double half_life = track->GetParticleDefinition()->GetPDGLifeTime();
and get 31197010000000 seconds I guess. What might be wrong there? I attached the output json-format file with produced isotopes within an event of 300,000 protons. My current goal is to calculate the activities of produced isotopes.

Activities.json.txt (9.6 KB)

Thanks for your help!

Ihor

[mkelsey]

@imelnyk

const G4double half_life = track->GetParticleDefinition()->GetPDGLifeTime();

That’s not the “half life,” it’s the exponential lifetime: dN/dt = exp(-t/LifeTime). That’s more useful for the code, and is consistent with how we deal with particle lifetimes. Half life = LifeTime * log(2).

@imelnyk

31197010000000

If that’s just the numeric value, it’s probably in nanoseconds (Geant4’s internal time unit). If you want to know the lifetime in seconds, you should print

  G4cout << "lifetime = " << life_time/second << " s" << G4endl;

Doing both conversions at once, I get a half-life of 218,379 seconds, or 2.53 days. That seems wrong; it should be 36,000 seconds (6 hours).

[jrellin]

I think there is a math error somewhere, I just can’t see it. 31197010000000 nanoseconds = 31197 seconds = 8.67 hours

ln(2) * 8.67 hrs = 6 hours which is correct.

[mkelsey]

My fault, Justin. I miscounted the zeroes at the end! I used “311970”, when it should have been 31197, as you say.

[imelnyk]

@mkelsey and @jrellin thank you for the explanation and advice! Now it works properly and I got 21624.12 seconds, what is corresponds to about 6 hours, of 99mTc half-life.

Sincerely, Ihor