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Forum: Hadronic Processes
Re: Question problems with G4RadioactiveDecay in geant4.9.4 (Susana Cebrian)
Date: 01 Apr, 2011
From: Laurent Desorgher <Laurent Desorgher>

Dear Susana,

I am looking right now at the different problems that you describe below. When I have some answers I let you know. Could you please in the mean time post your message as a bug report, if not already done. The problem that you list below will then officially be recognized as a Geant4 bug to solve!

Best regards

Laurent Desorgher

On Mon, 28 Mar 2011 08:04:58 GMT, Susana Cebrian wrote:

> Dear all,
> 
> We are interested in the simulation of radioactive decays of isotopes
> inside a detector, that is, all the emissions generated are relevant for
> us. We encountered problems in the past using the Radioactive Decay
> Model mainly due to the missing energy in beta- and EC emitters, as
> reported in problem report #1001(
> http://bugzilla-geant4.kek.jp/show_bug.cgi?id=1001 ). When using the
> last available version 4.9.4.p01, many of these problems have been
> solved, although some remain and also some new issue has appeared.
> 
> Our particular doubts, using the last version, are the following:
> 
> 1) From the sequence of isotopes in the natural radioactive chains,
> there are still problems for 228Ra (from 232Th chain) and 227Ac (from
> 235U chain), both beta- emitters with Q around 45 keV. In an ideal
> detector registering all the emissions, we expect a superposition of
> several beta spectra starting at the energies of the excited levels of
> daughters, but this expectation is not acomplished. Beta shapes start in
> some cases below the level energies, so it seems that there is still
> some missing energy (I attach the spectrum obtained for 227Ac).
> 
> 2) Concerning the electron energy spectrum for a beta- decay, I would
> like to know if as stated in the forum post (
> http://hypernews.slac.stanford.edu/HyperNews/geant4/get/hadronprocess/766.html
> ) and as it seems having a glance at the code in G4RadioactiveDecay.cc,
> LoadDecayTable(), case BetaMinus:, the considered shape is still always
> that of allowed transitions, and if the correction implemented in
> version 4.9.4 at G4RadioactiveDecay.cc suggested in the problem report
> #1068 ( http://bugzilla-geant4.kek.jp/show_bug.cgi?id=1068 ) is
> exclusively for 40K isotope. Our problem here is the following. The beta
> spectrum shape obtained for 40K with previous version (9.3.p02) agreed
> very well with the spectral information obtained from the book "Table of
> Isotopes" (Wiley, 1999) coming apparently from calculation having into
> account the order of forbiddenness, while after the specific correction
> for 40K implemented in the new version (9.4.p01) the agreement is much
> worse. The following table shows the comparisons:
> 
> energy range (keV) % Simulation (geant4.9.3.p02) % Tables % Simulation
> (geant4.9.4.p01) 0 a 10 0.49 0.495 0.403 10 a 20 0.51 0.51 0.41 20 a 40
> 1.1 1.1 0.87 40 a 100 3.9 3.9 3.02 100 a 300 18.0 17.9 13.8 300 a 600
> 32.0 32 27.4 600 a 1300 33.3 33.4 43.4 >1300 0.001 0.000326 0.0016 <E>
> 453.9 455 525.8
> 
> Mean energy <E> is calculated over 40K decays (not over electrons
> emitted in beta decays). We have checked that for other isotope (210Bi,
> first-forbidden transition) the agreement of the simulated beta spectrum
> with the information on Tables is also very good with the previous
> version. Are we misunderstanding anythig?
> 
> 3) It seems that the decay of 234Th (from 238U chain) is not properly
> reproduced in version 4.9.4.p01. * According to tables of isotopes, the
> beta decay ends almost always to the metastable state of 234Pa at 73.92
> keV, either directly (70.3%, according to /RadioactiveDecay3.3/z90.a234
> file) or through excited states with higher energy. The 234mPa decays
> beta- (mainly to the ground state of 234U, 98.2% from
> /RadioactiveDecay3.3/z91.a234 file) having a negligible probability of
> IT to the ground state of 234Pa (0.16%). * From the simulation, however,
> I encounter that in many cases (roughly, 70%) 234Pa[0.0], that is the
> ground state, is produced. Its beta- decay is very different from that
> of the metastable state, giving rise to the emission of a lot of gamma
> lines from 234U deexcitation. This problem was not present in previous
> version (I checked 9.3.p02) where 234Pa[73.9] state was correctly
> produced. Are you aware of this problem? Can be avoided in some way?
> 
> Many thanks for your help in any of these questions, Susana Cebrian
> 
>    Attachment:
>       http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2011/03/28/00.57-60078-SimulacionClara_ac227.txt
> 

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1 None: Re: problems with G4RadioactiveDecay in geant4.9.4   (Susana Cebrian - 01 Apr, 2011)
(_ None: Re: problems with G4RadioactiveDecay in geant4.9.4   (Laurent Desorgher - 14 Apr, 2011)
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