hi everyone! Now I am trying to get cross sections for photonuclear reactions (gamma, n). So I have gamma beam with energy from 0.1 MeV up to 50 MeV and gold target. And I want to get cross sections for the next reactions for different gamma beam energy: Au197 + gamma = A196 + n, Au197 + gamma = A194 + 3n. But I see that cross section for these tro reaction are the same. Only cross sections for Au197 + gamma = A194 + 3n start from about 23 MeV. Could you tell why? Thank you in advance!
Which physics list are you using?
QGSP_BIC_HP *pl = new QGSP_BIC_HP;
pl->RegisterPhysics(new G4EmStandardPhysics_option4());
pl->RegisterPhysics(new G4DecayPhysics());
pl->RegisterPhysics(new G4RadioactiveDecayPhysics());
So, as I understood in G4PhotoNuclearCrossSection.cc in the method GetElementCrossSection we don’t have difference for Au197 + gamma = A196 + n, Au197 + gamma = A194 + 3n reactions. So how can I get cross section for them separately?
G4double
G4PhotoNuclearCrossSection::GetElementCrossSection(const G4DynamicParticle* aPart,
G4int ZZ, const G4Material*)
{
const G4double Energy = 30*MeV;
if (Energy<THmin) return 0.;
G4double sigma=0.;
if(ZZ!=lastZ) // Otherwise the set of parameters is ready
{
lastZ = ZZ; // The last Z of calculated nucleus
if(GDR[ZZ]) // Calculated nuclei in DB
{
lastGDR=GDR[ZZ]; // Pointer to prepared GDR cross sections
lastHEN=HEN[ZZ]; // Pointer to prepared High Energy cross sections
lastTH =eTH[ZZ]; // Energy Threshold
lastSP =spA[ZZ]; // Shadowing coefficient for UHE
}
else
{
G4double Aa = nistmngr->GetAtomicMassAmu(ZZ); // average A
G4int N = (G4int)Aa - ZZ;
G4double lnA=G4Log(Aa); // The nucleus is not found in DB. It is new.
if(Aa==1.) lastSP=1.; // The Reggeon shadowing (A=1)
else lastSP=Aa*(1.-shc*lnA); // The Reggeon shadowing
lastTH=ThresholdEnergy(ZZ, N); // Energy Threshold
lastGDR = new G4double[nL]; // Allocate memory for the new
// GDR cross sections
lastHEN = new G4double[nH]; // Allocate memory for the new
// HEN cross sections
G4int er=GetFunctions(Aa,lastGDR,lastHEN); // new ZeroPosition and
// filling of the functions
if(er<1) G4cerr << "***G4PhotoNucCrossSection::GetCrossSection: A="
<< Aa << " failed" << G4endl;
GDR[ZZ]=lastGDR; // added GDR, found by AH 10/7/02
HEN[ZZ]=lastHEN; // added HEN, found by AH 10/7/02
eTH[ZZ]=lastTH; // Threshold Energy
spA[ZZ]=lastSP; // Pomeron Shadowing
} // End of creation of the new set of parameters
}// End of parameters udate
//
// =================== NOW the Magic Formula ===================
//
if (Energy<lastTH)
{
lastE=Energy;
lastSig=0.;
return 0.;
}
else if (Energy<Emin) // GDR region (approximated in E, not in lnE)
{
sigma=EquLinearFit(Energy,nL,THmin,dE,lastGDR);
}
else if (Energy<Emax) // High Energy region
{
G4double lE=G4Log(Energy);
sigma=EquLinearFit(lE,nH,milE,dlE,lastHEN);
}
else // UHE region (calculation, but not so frequent)
{
G4double lE=G4Log(Energy);
sigma=lastSP*(poc*(lE-pos)+shd*G4Exp(-reg*lE));
}
// End of "sigma" calculation
if(sigma<0.) return 0.;
return sigma*millibarn;
}
You might try the ShieldingLEND physics list. Currently LEND is the only Geant4 model which can separate the final states of a (gamma, n) reaction. However, I’m not an expert on this model so I don’t know if n and 3n are explicitly treated.
Thank you for this! So maybe someone know how could I get photonuclear cross sections from LEND physics list?
1- you need to download LEND data file and set the corresponding environment variable G4LENDDATA
2- below, a simplified physics constructor for example Hadr03 (and Hadr06, Hadr07 …) which uses Lend model and cross sections.
GammaNuclearPhysics.cc.txt (3.1 KB)
Thank you for your reply! Now I know how to use this physics list. But I want to get the values for cross sections of nuclear reactions with different gamma energies. How can I get them?
Any solutions for this problem?
what do you mean by “different gamma energy” ? above 20 MeV ?
1- with Hadr03 you can print values of cross section for any energy below 20 MeV
2- for a realistic simulation use ShieldingLEND physics list, as suggested by Dennis.
I want to get cross section like on the image. But the problem is that I have the same CS for Au197 + gamma = A196 + n and Au197 + gamma = A194 + 3n. Now I use ShieldingLEND physics list.
And when I use ShieldingLEND I get:
Code:
G4LENDCrossSection* lend = new G4LENDCrossSection;
const G4DynamicParticle* aPart = step->GetTrack()->GetDynamicParticle();
G4StepPoint* point1 = step->GetPreStepPoint();
const G4Material* material = point1->GetMaterial();
const G4Element* element = material->GetElement(0);
const G4Isotope* isotope = element->GetIsotope(0);
G4double xs2 = lend->GetIsoCrossSection( aPart , isotope->GetZ() , isotope->GetN() , isotope ,element , material );
cout << xs2 << endl;
From the terminal:
*** G4Exception : LENDCrossSection-01
issued by : G4LEND::GetIsoCrossSection(,)
is unexpectedly called.
*** Fatal Exception *** core dump ***
G4WT0 > G4Track (0x7f290c3f57e0) - track ID = 1, parent ID = 0
G4WT0 > Particle type : gamma - creator process : not available
G4WT0 > Kinetic energy : 0 eV - Momentum direction : (0,0,1)
G4WT0 > Step length : 7.61299 mm - total energy deposit : 0 eV
G4WT0 > Pre-step point : (0,0,-100) - Physical volume : phys0 (G4_Au)
G4WT0 > - defined by : not available
G4WT0 > Post-step point : (0,0,-92.387) - Physical volume : phys0 (G4_Au)
G4WT0 > - defined by : conv - step status : 4
G4WT0 > *** Note: Step information might not be properly updated.
Any advices, please?
below a run of Hadr03 (with Bertini cascade) : macro and output.
As you can see branching ratio for (g,n)Au196 and (g,3n)Au194 are different.
I did not try LEND model because on my local computer I cannot download LEND data (limited connexion). But if you have LEND data installed, you can try with the GammaNuclearPhysics.cc I have send you few day ago.
Au197.mac.txt (220 Bytes)
Au197.out.txt (2.4 KB)
I don’t know what photonuclear reaction data base is being used by these physics packages, but there are lots of graphs of energy dependent cross sections in IAEA-TECDOC-1178. You can check, gamma,3n is zero below ~23 MeV and rises to ~10 mbarn at 30-32 MeV. The gamma, peak at ~600 mbarn at ~13.5 MeV and drops to less than ~10 mbarn at the higher energies.
Hi, Thank you very much for your topic! I am trying to use the above codes to get the cross sections of 187Re(gamma, n) reaction. But the above codes don’t to specify the (gamma, n) reaction channel. So, how can I get what I want?