Re: A neutron problem

From: Alberto Fasso' <fasso_at_slac.stanford.edu>
Date: Mon, 30 Nov 2009 14:19:23 -0800 (PST)

There is a very simple way to get the neutron fluence in any
energy range. The result file from USRTRACK and USRBDX gives you, in
addition to the differential spectrum, also the cumulative spectrum at the
end of each energy interval (or each of the 260 energy groups below 20 MeV).
The integral fluence between any pair of energies (therefore in any energy
range) can be obtained as the difference between the corresponding values
of the cumulative spectrum.
As Francesco says, the energies can perhaps be approximated (3.927864 eV
instead of 4 eV and 10.33298 keV instead of 10 keV). Although the error is
small, you can make it even smaller by interpolation (linear, or even better
quadratic)

Alberto

On Sun, 29 Nov 2009, Francesco Cerutti wrote:

>
> Dear Ali,
>
> if you wish to get 3D maps of neutron fluence in the cavity corresponding
> to different neutron energy ranges, you can clone a USRBIN detector in
> your input and link a fluscw routine (to be activated by USERWEIG with
> WHAT(3)=3.0) where, according to the USRBIN index value (JSCRNG, for
> ISCRNG = 2), you prevent from scoring (setting LSCZER=.TRUE.) unless the
> neutron energy (PLA, check the sign according to the routine header) falls
> in the respective range. Of course the latter will be approximated by the
> group structure (your 4 eV limit becomes 3.927864 eV and the 10keV one
> 10.33298 keV).
> [If instead you look at the neutron spectrum averaged over the cavity as
> produced by USRTRACK, neutron fluences corresponding to the indicate
> ranges are obviously immediately given by the integration of the spectrum
> over these energy ranges].
>
> Hope this helps
>
> Francesco
>
> **************************************************
> Francesco Cerutti
> CERN-EN/STI
> CH-1211 Geneva 23
> Switzerland
> tel. ++41 22 7678962
> fax ++41 22 7668854
>
> On Sun, 29 Nov 2009, ali taheri wrote:
>
>> Dear Francesco,
>>
>> In fact my problem is to determine the neutron flux in these 3
>> ranges: 0 to 4 eV , 4eV to 10 keV and 10 keV to 10 MeV .
>> Of course I've used the pre-defined bins to plot neutron spectrum,
>> but in BNCT (is a kind of neutron therapy) it's needed also that we
>> know these fluxes separately!
>>
>> Thank you for your attention
>> Ali
>>
>> On 11/29/09, Francesco Cerutti <Francesco.Cerutti_at_cern.ch> wrote:
>>>
>>> Dear Ali,
>>>
>>> I miss the problem. The 260 pre-defined bins (from 20 MeV down to 1e-5
>>> eV)
>>> are indicated in the manual and are printed in the neutron scoring
>>> files.
>>> The transport of neutrons below 20 MeV cannot prescind from this
>>> binning
>>>
>>> Ciao
>>>
>>> Francesco
>>>
>>> **************************************************
>>> Francesco Cerutti
>>> CERN-EN/STI
>>> CH-1211 Geneva 23
>>> Switzerland
>>> tel. ++41 22 7678962
>>> fax ++41 22 7668854
>>>
>>> On Sun, 29 Nov 2009, ali taheri wrote:
>>>
>>>> Dear Fluka Users
>>>>
>>>> Hi
>>>> I am working on a simple Neutron source,there is a vacuum cavity
>>>> and I need to know the neutron fluence in thermal,epithermal and
>>>> fast ranges separately in the cavity.
>>>>
>>>> As I knew,in Fluka we can't specify energy bins for neutrons! please
>>>> help me to solve this problem.
>>>>
>>>> I'd be thankful to you for help
>>>>
>>>> Best Regards
>>>> Ali Taheri
>>>>
>>>>
>>>
>>
>
>

-- 
Alberto Fasso`
SLAC-RP, MS 48, 2575 Sand Hill Road, Menlo Park CA 94025
Phone: (1 650) 926 4762   Fax: (1 650) 926 3569
fasso_at_slac.stanford.edu
Received on Tue Dec 01 2009 - 13:32:46 CET

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