Dear Mo,
if I'm not misinterpreting your set-up, I'm afraid that neglecting neutron
transport in the target (due to the Ra cross section lack in the library)
is going to leave you with [almost] no neutron at all, since they are
expected to be produced there [mainly, and even exclusively if your proton
beam does not see any other material along its path]. So my suggestion was
intended to let you estimate the target activation only, assumed to be
dominated by the primary beam. For your surrounding geometry, not directly
impacted by the primary beam, no activation estimation gets achievable
without neutron transport in the target. Hence you can even DISCARD
NEUTRONs.
Another wild option - far from being recommendable - would be to associate
to your target material the low energy neutron cross section set of a
'similar' material, through the LOW-MAT card. This way the neutrons, which
are generated by the proton beam interaction in the target, would manage
to escape the latter and interact elsewhere, but their former transport in
the target would be wrong.
Therefore, all in all, your case is not prone to obtaining accurate
results.
Cheers
Francesco
**************************************************
Francesco Cerutti
CERN-EN/STI
CH-1211 Geneva 23
Switzerland
tel. ++41 22 7678962
fax ++41 22 7668854
On Fri, 17 Feb 2017, Benmerrouche, Mohamed wrote:
> Hi Francesco:
>
> Thank you so much for the suggestion. My target is about 1.5 mm which I assume is sufficiently thin enough to make neutron contribution to the activation of the target negligible.
> What FLUKA card should I use to discard neutron transport in the target only and keep neutrons transport elsewhere activated?
>
> Mo
> -----Original Message-----
> From: owner-fluka-discuss_at_mi.infn.it [mailto:owner-fluka-discuss_at_mi.infn.it] On Behalf Of Francesco Cerutti
> Sent: Friday, February 17, 2017 7:03 AM
> To: FLUKA discussion
> Subject: Re: [fluka-discuss]: missing neutron cross sections
>
>
> Of course I'm referring to the target activation only, without neutrons you will get no activation estimate elsewhere.
>
> On Fri, 17 Feb 2017, Francesco Cerutti wrote:
>
>>
>> Hi Mo,
>>
>> if you discard neutrons, which cannot be properly transported in the
>> absence of the respective cross sections, you will get an estimation
>> of the activation due to the primary beam, neglecting the contribution
>> of neutron reinteractions. If your target is sufficiently thin, such
>> an estimation may still make some sense (apart from uncertainties
>> related to the rather low proton energy).
>>
>> Cheers
>>
>> Francesco
>>
>>> Hi Mohamed,
>>
>>> I had a same prob with the neutron libraries for Tellurium.
>>
>>> Cheers,
>>> Shri
>>
>> (Srinidhi Bheesette)
>>
>> On 14 February 2017 at 06:16, Benmerrouche, Mohamed
>> <Benmerrouche_at_bnl.gov>
>> wrote:
>>
>>> Dear FLUKA experts/users,
>>>
>>> I am trying to setup an activation study with a 16MeV proton beam on
>>> Ra-226 target but when I run my input file FLUKA exits with the
>> following
>>> error message:
>>>
>>> ***** Neutron Xsec: ****
>>> **** Group limits, average energies, velocities and momenta start at
>>> location 10422717, end at location 10424884 (I*4 addr.) *****
>>>
>>> **** Low energy neutron xsec not found for some media 12 13 ****
>>> RADIUM
>>>
>>> Which indicate that low energy neutron cross sections for Ra-226 are
>>> not available in the FLUKA code. I checked the FLUKA manual section
>>> 10.4.1.2 and confirmed that there is NO entry for Radium.
>>>
>>> Any suggestions or thoughts on how to resolve this issue?
>>>
>>> Thanks,
>>> Mo
>>
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Received on Sat Feb 18 2017 - 00:32:02 CET