Re: Re: [fluka-discuss]: Contribution of different particles to the detector signal !

From: Vittorio Boccone <dr.vittorio.boccone_at_ieee.org>
Date: Fri, 25 Nov 2016 13:57:22 +0100

Dear Yang,

> 1."> However, the computational results are strange, gamma, neutron, and
> electron all have energy deposition, the most contribution is from electrons
> I don’t understand this phrase>"
>
> reply: I mean gamma ,neutron and electron all have energy deposition in
> the detector sensitive volume, but the maximum deposition is given by
> electrons, but electrons have not penetrated into the detector.
>
I think I understand now your problem, and it's clearly not related to
FLUKA. If the secondary (or further-generation) electron is generated
outside of your detector and has not enough energy to penetrate the
detector (or generate n+1 generation electrons and gamma which can) you
should not bother about them as they will not affect your signal creation.

2. "> > 1. [….] what is the small deposition value given by gamma and
> neutron? Is it the Non-ionising energy losses (NIEL)
> > I also partly don’t understand the question. Neutrons can generate
> nuclear recoils, which in turn ionise and excites atoms/molecules along the
> track. NIEL - when no nuclear reaction are involved - are essentially
> related to the stopping power effects which includes lattice displacement,
> etc…"
>
> reply: Based on the interpretation of Alberto Fasso,if all the energy
> deposition is from electron ionization, why
> do gamma and neutron have a energy deposition value?

You cannot generalize w/o specifying in detail the radiation field. Not all
the energy is lost in FLUKA through electron for all the processes. You
took out Alberto phrase from a more general context. Sure all the energy
lost through ionization losses will generate low energy electrons or
atomic/molecular excitations. The "fiction" you do in the simulation is to
account all the energy lost by delta rays to the original particle
interaction.


3. The contribution to what? If the don’t interact inside of the active
> area of your detector what are you supposed to include? The only thing you
> might want to include is radioactive decays if your radiation field
> contains particle which can activate materials.
> > If I understand correctly your question, you are asking how to separate
> - in the simulation results - the effect from different particle sources
> which compose your radiation field. (I also don’t get completely the sense
> of the question, perhaps you should try to get some help around to
> reformulate the question.)
> > Well the point is that you are modelling you simulation, so you can
> separate the sources and run the simulation cases separately so you can see
> the effect on you detector independently. I can’t suggest you the “two step
> method” as I don’t know/understand your specific simulation case.
>
> reply: I mean the contribution to the total signal of detector. Indeed,
> what I want to do is to separate the effect from different particle sources
> which compose the radiation field. Unfortunately, I cannot simply separate
> the sources and run the simulation cases separately for the reason that
> the radiation field comes from a beam loss on the beam tube or beam
> injection on a dump, the radiation field is complex, gamma and neutron both
> have a complex spectrum and I don't know how to model it like a simple
> source. And I don't know whether the "two-step methods" could solve the
> problem.
>
Ok, it's good that you start to describe your mixed radiation field.
Your detector will see only the effects of the particles crossing it. Each
particle has a history, a "father" process/interaction which generated it,
and "children" particles which were generated by the interaction.
 therefore the AUXSCORE card uses this information to understand how much
energy deposition was caused by a gamma, neutron or whatever else effect.


As Alberto write the DELTARAY card controls the threshold below which the
electrons (generated by other particles) will be considered delta-rays and
therefore included in the energy balance controlled by the AUXSCORE card
associated to a specific particle type.

If you need the full particle tree history following the primary
interaction you can always use the USERDUMP card, but this can generate a
lot of data.

I would first try to have under control the simulation of the detector
response for specific primaries. In real life you would do the same by
calibrating your detector response with specific particles and specific
energy relevant to your problem.

Second you need to get familiar with the particle fluences and spectra at
the detector using a few USRTRACK and USRYIELD cards.

Only then you can introduce the mixed radiation field. This can be achieved
by changing the source term.

Best
Vittorio


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Received on Fri Nov 25 2016 - 15:39:18 CET

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