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Keywords: nuclear gamma rays
Forum: Hadronic Processes
Re: Question Nuclear Gamma Emissions (Kazuyoshi Furutaka)
Date: 08 Aug, 2006
From: Kazuyoshi Furutaka <Kazuyoshi Furutaka>

I managed to find a way _to avoid_ the problem I encountered.

Let me describe what I observed.

I want to simulate cascades of gamma rays emitted following (thermal)
neutron capture by Nitrogen-14.  (Neutron separation energy of the
capture product, Nitrogen-15, is 10.833 MeV.)
To simulate the cascades I made two z7.a15 files, one in
$G4RADIOACTIVEDATA and the other in $G4LEVELGAMMADATA.
The file in the former directory contains the following entries:
  P 10833.30000  1.000E-15
                           IT         10833.30000  1.000E+00
The file in the latter directory lists the ENSDF evaluated level and
gamma data for 14N(n,gamma) reaction below the 10.833-MeV level, with
all the ICCs set to either 1.000e-20 or 0.000e+00.

The problem was that relative intensities of the emitted gamma ray
after populating the 10.833-MeV state were wrong ON A PC, specifically,
a machine with dual AMD Opteron CPUs running x86_64 Fedora Core 5.

Setting /gdrm/verbose 3 and observing the outputs, I saw the following
line
  "G4ContinuumGammaDeexcitation::CanDoTransition -  Excitation (energy value) ..."
on PCs on which I obtained correct results, while on the Opteron PC the
following line was displayed:
  "G4ContinuumGammaDeexcitation::CanDoTransition - CanDo".

The former line is displayed if
  excitation <= _levelManager->MaxLevelEnergy()
in source/processes/hadronic/models/de_excitation/photon_evaporation/\
  src/G4ContinuumGammaDeexcitation.cc.
This implies that on the Opteron machine
  excitation > _levelManager->MaxLevelEnergy()
for some reason.
So I added the data for levels above 10.833 MeV, and then I
observe the capture gamma rays with correct intensities.


By the way, in the discussion following the thread 186 of the
"Documentation and Examples" forum, I found that there're three
duplicated lines in the original $G4LEVELGAMMADATA/z7.a15 file
and reported it to someone, and the person told the duplicated
line won't cause any problem.
During my experimenting of the original as well as 14N(n,gamma)
z7.a15 files, I found that the gamma rays corresponding to the
duplicated lines are emitted TWICE AS OFTEN AS with only one
line.
The gamma rays on the duplicated lines correspond to the ones
which are marked as "multiply placed" (with either `@' or `&')
in the ENSDF "adopted levels and gammas" data.


Yours,
Kazuyoshi

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