Re: Cross section and radiation lenght!

From: jonathan pochon <jgpochon_at_iac.es>
Date: Fri, 31 Oct 2008 12:05:46 +0000

Dear Vasilis,

Firstly, thank you for your help.
I send your the input file Section.inp, it is a simple case with a 9-Be beam
on Al target, and I want to determine the inelastic cross section.

Looking the aluminum property from the basic output, "Inelastic Scattering
Length" is 13.68 cm that implies the 9-Be beam flux will be reduced
crossing the 5 mm Al target to reach 96% of his initial value. Using two
USRBDX, one for the "incoming" flux and the other for the "outgoing" one,
we see we have the same flux so it seems there are not inelastic reaction.

Then, looking information from USRYIELD it is said that the cross section is
about 0.45 barn it means 36 cm for the total scattering length.

I used PHYSICS card to add some "effects", like Ion-Splitting and/or
EM-Dissociation, to improve the realism of the simulations. I can change
some threshold like IONSPLIT
to obtain the cross section I want but I don't like doing this way. I'm sure there are basics things I didn't understand or use well.

Thank you.

Regards,

Jonathan

2008/10/29 Vasilis Vlachoudis <Vasilis.Vlachoudis_at_cern.ch>

> Dear Jonathan,
>
>
>
> Could you please send us the input file or the output file of usrbdx to
> understand what you are doing
>
>
>
> Best Regards
>
> Vasilis
>
>
>
> *From:* jpochon_at_gmail.com [mailto:jpochon_at_gmail.com] *On Behalf Of *jonathan
> pochon
> *Sent:* Monday, 27 October 2008 19:00
> *To:* Vasilis Vlachoudis
> *Cc:* fluka-discuss_at_fluka.org
> *Subject:* Re: Cross section and radiation lenght!
>
>
>
> Dear Vasilis,
>
> Thank you for your help.
> I still have a problem with my cross-check evaluation for cross section.
> I thought it came from USRYIELD but it may be come from USRBDX.
>
> I use 7-Li, with 100 MeV/c per nucleon, on lead target, 0.1 cm thin. For
> 7-Li, USRYIELD gives me the following cross-section = 1.8 barn, but If
> I'm looking with USRBDX the 7-Li flux ratio between before and after the
> lead target, I have Flux/Flux-initial = 0.1 when I am hoping
> Flux/Flux-initial = 0.994. May be the way I use it, it's wrong?
>
> USRBDX 99. HEAVYION -42. TARGET VOID
> 100.0BdxAp
> USRBDX 10.0 0.01 100.
> &
>
> What can I do to debug that, some tips to be sure what I am looking at?
>
> Thanks.
>
> Regards,
>
> Jonathan
>
> 2008/10/24 Vasilis Vlachoudis <Vasilis.Vlachoudis_at_cern.ch>
>
> Dear Jonathan,
>
> the scattering length is the average distance to have an interaction and it
> is equal to the inverse of the macroscopic cross section,
>
> Scattering_length = 1 / (Na/A * rho * cross-section)
>
> Na = Avogadro number
> A = atomic mass
> rho = density
>
> Vasilis
>
>
>
> jonathan pochon wrote:
>
> Hi,
>
> I'm checking some cross sections with simple set-up before
> to use something complicated. I'm sometimes surprised
> with USRYIELD cross section, and I want to be sure on my
> understanding.
>
> For this reason, I would like to know how to extract initial cross
> section that FLUKA uses for example with a proton beam and
> a carbon target. I saw the standard output with scattering length
> but I'm not sure it's the scattering length from
> Cross-section = cst * Scatt-Length˛
>
> It must be a vocabulary problem or something like that.
>
> Thanks,
>
> Jonathan
>
>
>
>
>

Received on Sat Nov 01 2008 - 14:34:24 CET

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