I would like to obtain the gamma spectra of the reaction Cl37(n,g) Cl38 and compare it with measured data from NNDC (CapGam - 37CL(N,G) E=THERMAL). To do so, I have started from the Geant4 Activation example (examples/extended/radioactivedecay/Activation · master · geant4 / geant4 · GitLab), and in the run.mac file I set
/testhadr/det/setIsotopeMat Cl37 17 37 2.48 g/cm3
/analysis/h1/set 4 800 0 8 MeV #energy spectrum of emerging gamma
And here is the energy spectrum that I obtained, compared with NNDC.
I also tried Ni60 and then again, the spectra do not correspond.
What am I doing wrong? I also tried different physics list for neutron precision transport, but it did not have any effect. Should I try to select the process radioActivation? I am using G4NDL4.7 and geant4.11.2.1.
Thank you so much!
Geant4 Version: geant4.11.2.1 Operating System: Rocky Linux 9 Compiler/Version: gcc version 11.4.1 CMake Version: cmake version 3.20.2
Hi,
Thank you so much for taking the time to look into this.
I did exactly as you said, except that I replaced
/testhadr/det/setIsotopeMat Cl37 17 37 2.48 g/cm3
with
/testhadr/det/setIsotopeMat Ni60 28 60 2.48 g/cm3
since I saw in a previous topic (Question in neutron capture (Gd155(n, gamma)Gd156) reaction - #6 by John_McFee) that NNDC data and Geant4 simulation were found to match for Ni60 activation.
However, using the example Hadr03 instead of Activation does not seem to work any better…
In the previous topic above (Question in neutron capture (Gd155(n, gamma)Gd156) reaction - #6 by John_McFee), I obtained good agreement for Ni60 when HP parameters were set as follows:
SetSkipMissingIsotopes( true );
SetDoNotAdjustFinalState( true );
SetUseOnlyPhotoEvaporation( true );
SetNeglectDoppler( true );
With SetDoNotAdjustFinalState( true ) and all the others were false, I got only fair agreement.
Also, the results in that thread were obtained for Geant4 10.7.2 with G4NDL4.6
I suggest setting the HP parameters appropriately in Hadr03.cc, recompile and try again.
thank you for your anwser. I specified in the mac file
/process/had/particle_hp/use_photo_evaporation true
/process/had/particle_hp/do_not_adjust_final_state true
/process/had/particle_hp/skip_missing_isotopes true
/process/had/particle_hp/neglect_Doppler_broadening true
as you suggested, but nothing changed.
I have also tried different physics lists, namely G4HadronPhysicsFTFP_BERT_HP, G4HadronPhysicsQGSP_BIC_HP, and G4HadronPhysicsQGSP_BERT_HP, but it makes very little difference.
I keep looking and I’m still very open to suggestions!
1- PhysicsList of Hadr03 does not include radioactive decay of Cl38 (see attachement for rdecay01: Cl38.mac.txt). This is a main difference with example Activation.
NNDC data correspond to Hadr03 situation.
2- Ni61 is stable. Therefore Hadr03 and Activation will give more on less similar spectrum.
Comparing with NNDC, as you noticed, gamma rays above 7 MeV are quasi missing in all Geant4 physics variants.
There is something going on that I do not understand. In Nov 2021 using Geant4 10.7.2 as mentioned in above thread (Question in neutron capture (Gd155(n, gamma)Gd156) reaction - #6 by John_McFee) I obtained good agreement between the NNDC database and Geant4 using a simple 25meV neutron beam geometry with a thin (1cm) 60Ni target in vacuum. The spectrum looked like the NNDC spectrum from their website (see NNDC spectrum above and my spectrum immediately following). For the top 36 out of 240 capture gamma rays from NNDC the energies agreed to within 2.2 ± 2.6 keV and the intensities (normalized to 100%) to within 0.810± 3.750 (see spectrum and screenshot of spreadsheet)
I used Physics list: QGSP_BERT_HP
HP parameters: SetSkipMissingIsotopes( true ); SetDoNotAdjustFinalState( true ); SetUseOnlyPhotoEvaporation( true ); SetNeglectDoppler( true );
If I changed all the parameters to false except: SetDoNotAdjustFinalState( true ) the spectrum was very different and there was a poor match to NNDC
Because of the current thread, I decided to rerun my identical code using Geant4 11.2.2, again with
Physics list: QGSP_BERT_HP
HP parameters: SetSkipMissingIsotopes( true ); SetDoNotAdjustFinalState( true ); SetUseOnlyPhotoEvaporation( true ); SetNeglectDoppler( true );
The results were completely different from those of Geant4 10.7.2 with poor agreement between Geant and NNDC. I also varied the HP parameters but the results were very similar to one another.
I would expect that there are differences between G4NDL4.6 (from G4 10.7.2) and G4NDL4.7.1 (G4 11.2.2), but I would not have thought them to be that dramatic. Has something changed in the way the data bases are processed or am I missing something obvious? I am puzzled.
