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Forum: Hadronic Processes
Re: Question Giant Dipole Resonance photo-neutron production in medical linac (Alessandro Berra)
Re: None Re: Giant Dipole Resonance photo-neutron production in medical linac (Dennis H. Wright)
Re: None Re: Giant Dipole Resonance photo-neutron production in medical linac (Alessandro Berra)
Re: None Re: Giant Dipole Resonance photo-neutron production in medical linac (michel maire)
Re: Idea Re: Giant Dipole Resonance photo-neutron production in medical linac (Vladimir Ivanchenko)
Date: 27 May, 2013
From: Alessandro Berra <Alessandro Berra>

On Sun, 26 May 2013 19:25:04 GMT, Vladimir Ivanchenko wrote:
> Hello,
> 
> Be careful: if you deactivate any process you will have wrong physics and results will not be reliable. You need to run with high statistics or apply biasing methods. To understand the level of the problem you may use 
> 
> $G4INSTALL/examples/extended/electromagnetic/TestEm0 
> 
> to study EM cross sections and
> 
> $G4INSTALL/examples/extended/hadronic/Hadr00 
> 
> to study gamma-nuclear cross section. 
> 
> The simplest biasing method is to multiply small cross section by a factor, which increase the probability of events of interest but does not change significantly overall tracking. If rare process cross section will be enhanced too much one need apply extra which is out of scope of initial discussion.
> 
> VI
> 

Hello,

thank you very much for your suggestion. I ran TestEm0 and Hadr00 and at 10 MeV the total EM cross section for gammas (phot+compt+conv) is ~15 barn, while the inelastic cross section due to GDR is ~0.1 barn (with a peak of ~0.4 barn at 14 MeV).

I know that the original intent of the thread was another one, but how can I increase the GDR cross section inside the physics list? Considering the values I have found, an increase of a factor 10x is needed to speed-up the simulation.

Is this factor too much for the biasing approach you suggest?

Thank you in advance

Alessandro

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