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Forum: Hadronic Processes
Re: Question bug in HP for gammas? (Zoltan Elekes)
Date: 08 Jun, 2012
From: Malachi Schram <Malachi Schram>

Hi Zoltan and developers,

I believe we have identified the same problem.
My simulated results for 35Cl(n,p) reaction yield incorrect energies for the excited photons.
I believe I've localized the problem to the G4NeutronHPInelasticCompFS class.
In fact, the excited states are correct, however, there is a few things I do not understand (see below).

I added print statements within the geant4 source code to follow the calculations. The following is what I found:

G4NeutronHPPInelasticFS::ApplyYourself()
Incident Neutron KE: 4.703 E:944.268
Target Mass: 34.6592 --> On-the-fly calculation, not using the actual material properties defined in my detector constructor
Total initial E: 33508.9 MeV
Residual Mass: 34.6599 --> Calculates based on process, in my case it's a (n,p) reaction therefore it's using the G4NeutronHPPInelasticFS class.
Reaction Product KE: 4.70297 --> Good, this is what I initially put in the system

G4NeutronHPInelasticCompFS::SelectExitChannel()...
Available Energy: 5.31986 --> This is correct, just add the energies (Q+KE)
Gamma Excited Energy[1]: 1.99133 --> This is the 2nd excited state for 35S which is a possible decay mode:)

===> Before adjust_final_state() method <===
Number of secondaries: 5
proton KE:3.37405 MeV E:941.646 MeV
gamma KE:1.9936 MeV E:1.9936 MeV
gamma KE:0.419755 MeV E:0.419755 MeV
gamma KE:0.418385 MeV E:0.418385 MeV
S35[0.0] KE:0.215828 MeV E:32565.5 MeV
Gamma energy: 2.83174 MeV
Total energy: 33510 MeV

===> After adjust_final_state() method <===
Number of secondaries: 5
proton KE:3.37405 MeV E:941.646 MeV
gamma KE:0.891849 MeV E:0.891849 MeV
gamma KE:0.419755 MeV E:0.419755 MeV
gamma KE:0.418385 MeV E:0.418385 MeV
S35[0.0] KE:0.218552 MeV E:32565.5 MeV
Gamma energy: 1.72999 MeV
Total energy: 33508.9 MeV

1) Why are there 2 extra gammas? I don't see any possible decay chains (still looking)
2) Why was the excited state gamma scaled to conserve energy?
   The energy of the excited state gammas should never be changed.
   It would have been better to scale the proton

I will try geant4.9.2.x and compare results.

Cheers,

Malachi

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1 More: Re: bug in HP for gammas?   (Malachi Schram - 11 Jun, 2012)
1 Note: Re: bug in HP for gammas?   (Zoltan Elekes - 11 Jun, 2012)
(_ Feedback: Re: bug in HP for gammas?   (Malachi Schram - 14 Jun, 2012)
2 None: Re: bug in HP for gammas?   (Koi, Tatsumi - 16 Jul, 2012)
1 Feedback: Re: bug in HP for gammas?   (Malachi Schram - 17 Jul, 2012)
2 None: Re: bug in HP for gammas?   (Zoltan Elekes - 18 Jul, 2012)
1 Question: Re: bug in HP for gammas?   (Mikhail - 23 Jul, 2012)
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