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Forum: Hadronic Processes
Re: None Alpha n reactions in geant4 (Zachary Babbitt)
Re: None Re: Alpha n reactions in geant4 (michel maire)
Re: Question Re: Alpha n reactions in geant4 (Neha Dokania)
Date: 10 Oct, 2014
From: Jose Manuel Quesada <Jose Manuel Quesada>

Hi all,

           let me add a comment, in the sense that has already been done 
several times in in the past. Given the very low energies, and masses 
your reaction will proceed via very simple equilibrium de_excitation 
mechanisms, which in Binary cascade is Fermi-BreakUp (if A<17, as in 
your case) or evaporation (A>17). Bertini uses its own version of 
equilibrium de_excitation models, as did INCL in the past (now it uses 
the same de_excitation models as Binary). But in any case those models 
are intended as  final de-excitation stages after string or cascade 
models (starting at much higher energies, above GeV) have done their 
job. By no means they are intended as "doorway" models.

  Fermi Break-Up model considers the different possible partitions of 
the excited nuclear system  (13C in your case, if target is 9Be), and 
samples them according to probability distribution coming from phase 
space availability  arguments. Just a theoretical model. If it comes out 
(as it seems that happens in your case) that the partitions with 1n+ 
residuals (or residuals) never "win" (or even are simply forbidden by 
the model).. you end up without neutrons. Just a model. Even if, just by 
simulating many, many particles, you get some neutrons, you shouldn't  
expect to reproduce experimental data at such low energies and light 

  The same applies to alphas on quartz at these energies.

  You should resort to evaluated data, which is what G4ParticleHP (under 
development) is intended for.


              Jose Manuel

On 10/09/2014 05:04 PM, Neha Dokania wrote:
> *** Discussion title: Hadronic Processes
> Hi,
> I have used Hadr03 Physics list with Geant4.9.5.p01. But I don't see any
> neutrons being produced as secondaries from 2-20MeV alpha on Be. Same
> happened with QGSP_BERT, QGSP_BIC physics lists.
> Any help will be much appreciated.
> On Fri, 18 Apr 2014 09:03:10 GMT, michel maire wrote:
>> On Wed, 16 Apr 2014 17:09:10 GMT, Zachary Babbitt wrote:
>>> Hello,
>>> I am attempting to simulate an (alpha, n) reaction in Geant4 and I cannot
>>> figure out how to do this. I have registered the  QGSP_BERT_HP physics list
>>> as well as the QGSP_BIC_HP physics list and no neutrons are showing up in
>>> the process. Do I need to fully implement my own physics list to do this,
>>> and if so, are there any examples I can reference? I'm working with alpha
>>> particles that are from 5-20 MeV range which are being thrown into a
>>> cylinder of quartz. Thank you.
>>    Your list of physics must include one of the physics constructors in
>>     source/physics_lists/constructors/ions
>>   In attachement an example of Hadr03 run. See the of this example.
>>     Attachment:
> -------------------------------------------------------------
> Visit this GEANT4 at message (to reply or unsubscribe) at:

José Manuel Quesada Molina
Departamento de Física Atómica, Molecular y Nuclear
Facultad de Física
Universidad de Sevilla
Apartado 1065
41080 Sevilla, España

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