Re: RE: Please suggest

From: Sunil C <csunil11@gmail.com>
Date: Fri May 23 2008 - 11:03:32 CEST

Hi all

I missed one important point about the absolute number of neutrons.
While it is not important for energy sampling, it is important to scale the
results to the beam current at the end of the simulation.

For protons, there are several empiral relations that can give the number of
neutrons per proton. I have not seen such a relation for alpha particles.

Regards
Sunil

On 5/22/08, Sunil C <csunil11@gmail.com> wrote:
>
> I have the following comments
>
> ALICE91 if used correctly (input options such as level density, inverse
> cross section etc) can give reasonable emission spectra. A thick target can
> be assumed to be a combination of several thin targets and the incident
> energy can be changed in each slab and the emission calculated again, till
> the projectile energy cannot produce neutrons (typically the Coulomb
> barrier). A superimposition of all the spectra can be produced. The absolute
> numbers are not important as in the source subroutine you can have
> a cumulative distribution for sampling the energy.
>
> The range of alpha particles is not not large (micrometer to mm). So the
> sampling volume is small. Not much uncertainty in the starting point for
> further neutron transport simulations especially for shielding calculations.
> For the same reason, neutron attenuation also can be neglected.
> Overall It can be a good approximation.
> But yes, I would like to see how the comparison is with the RQMD.
>
> All, Of course till the BME for low energy projectiles is included in
> FLUKA.
>
> Regards
> Sunil
>
>
> On 5/21/08, Markus Brugger <Markus.Brugger@cern.ch> wrote:
>>
>> Hi,
>>
>> after some discussions we have the following comments and suggestions
>> for your problem:
>>
>> - not knowing ALICE91 we assume that what you get is particle and energy
>> spectra originating from the actual alpha interaction
>> - from a technical point-of-view there is no problem in using this as a
>> source for a subsequent FLUKA calculations, however it's applicability
>> remains questionable due to the following points
>> o if we understand your email correctly you would use the
>> pre-calculated neutron and photon spectra as a source impinging on the
>> Fe cylinder, thus you loose the transport part of the remaining (after
>> the interaction) thick Ta target
>> o there might be a certain problem in the choice of the energy you use
>> as input for ALICE, i.e., as the target is thick interactions will not
>> only occur at the starting beam energy, but also further below
>> o even if you consider the latter in terms of using different
>> energies, thus different production spectra, the problem remains where
>> to correctly start the 2nd FLUKA simulation (in the thick target)
>> - as accuracy is generally difficult to judge for both ALICE (we don't
>> know), as well as RQMD when lowering the production threshold (alphas at
>> 50 MeV), we can only suggest to compare the following approaches
>> + set the production threshold of RQMD down to 50 and do a
>> calculations -> this way you get the 'location' of the interactions
>> sampled correctly (at least down to 50MeV)
>> + use the ALICE spectra as input to your calculations and start the
>> 2nd (FLUKA) calculations=20
>> o downstream of the Ta target
>> o at the start of the Ta target
>> o at a calculated average penetration depth
>>
>> hope this helps you in some respect, cheers
>>
>> Markus
>>
>>
>> > -----Original Message-----
>> > From: owner-fluka-discuss@mi.infn.it [mailto:owner-fluka-
>> > discuss@mi.infn.it] On Behalf Of rravi@veccal.ernet.in
>> > Sent: Sonntag, 18. Mai 2008 08:42
>> > To: Markus Brugger; fluka-discuss@fluka.org
>> > Subject: Re: RE: Please suggest
>> >=20
>> > Dear Mr. Markus Brugger, and Others of the Forum,
>> > Thanks for your detailed reply. My source itself is
>> > less than 100 MeV/n and as you say if the default RQMD is set to 100
>> > MeV/nucleon for Heavy Ions, there is no point in setting "TRANSPORT"
>> > less ( as initial INTERACTION itself can't be compromised). Hope BME
>> > model will be fully implemented in Future versions for public domain.
>> > In the mean time, I would like to request experts, if I use neutron
>> > Spectrum input in Fluka ( Spectrum generated from codes like ALICE91
>> > etc for 320 MeV Falling on Ta) to interact on Fe Cylinder ( as
>> > described in problem described earlier) and estimate the resultanting
>> > neutron and photon flux, will it be anywhere near approximation of the
>> > problem described earlier ?
>> > Kindly advise me.
>> >=20
>> >=20
>> > R. Ravi Shankar
>> > Scientific Officer,
>> > Health Physics Unit,
>> > VECC, 1/AF, Bidhan Nagar,
>> > Kolkata 700 064.
>> > India. Tel: +91 033 23371230-34 extn:3153
>> >=20
>> >=20
>> > ----- Original Message -----
>> > From: Markus Brugger <Markus.Brugger@cern.ch>
>> > Date: Friday, May 16, 2008 3:03 pm
>> > Subject: RE: Please suggest
>> >=20
>> > > Hi,
>> > >
>> > > there is another problem related to your question which was missed
>> > > yesterday. As your source particles are 320 MeV Alphas FLUKA
>> > > currently
>> > > performs the 'transport', however does not perform 'interactions'
>> > > (with
>> > > the default RQMD being set to 100MeV/nucleon). To a limited
>> > > extend, the
>> > > sampling of 'interactions' could be reached by lowering the
>> > > threshold of
>> > > the RQMD model (PHYSICS card) but again the !!! lowest !!!
>> > > possible
>> > > limit (for 'interactions') is 51MeV, thus only of limited use in
>> > > your
>> > > case. In addition, by lowering this limit, especially for alphas,
>> > > the
>> > > accuracy of the results remains questionable.=3D20
>> > >
>> > > Besides, and as a possible outlook for future FLUKA releases, a
>> > > new BME
>> > > model is currently under development however not yet available for
>> > > public use.
>> > >
>> > > Please find further information also in the following answer of
>> > > the
>> > > fluka-discuss list:
>> > >
>> > >
>> http://www.fluka.org/web_archive/earchive/new-fluka-discuss/0885.html
>> > >
>> > > cheers
>> > >
>> > > Markus
>> > >
>> > > >> > > -----Original Message-----
>> > > > > From: owner-fluka-discuss@mi.infn.it [owner-fluka-
>> > > > > discuss@mi.infn.it] On Behalf Of rravi@veccal.ernet.in
>> > > > > Sent: Dienstag, 13. Mai 2008 08:04
>> > > > > To: fluka-discuss@fluka.org
>> > > > > Subject: Please suggest
>> > > > >
>> > > > > Hi All,
>> > > > >
>> > > > > I am new to this forum and also a novice user of Fluka.
>> > > My =3D
>> > > best
>> > > > > regards to those great people who developed and made it
>> > available.
>> > > > > I have a problem. Can any body give me a suggestion ?
>> > > > >
>> > > > > I want to estimate the photon and neutron fluence emerging
>> > > out of
>> > > > the
>> > > > > system
>> > > > > The system is:
>> > > > > 320 MeV Alpha beam falling on thick target of Tantalum; the =3D
>> > > emerging
>> > > > > neutrons etc falling on Fe cyclinder.
>> > > > > *******
>> > > > >
>> > > > > Is it possible to do that with 320 MeV alpha in Fluka?
>> > > > >
>> > > > > With best regards to all of you,
>> > > > >
>> > > > > R. Ravi Shankar
>> > > > > Scientific Officer,
>> > > > > Health Physics Unit,
>> > > > > VECC, 1/AF, Bidhan Nagar,
>> > > > > Kolkata 700 064.
>> > > > > India. Tel: +91 033 23371230-34 extn:3153
>> >=20
>> > >
>> > >
>>
>>
>
Received on Sat May 24 21:09:49 2008

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