Re: Neutron fluence in spallation reaction

From: Mary Chin <>
Date: Wed, 16 May 2012 19:24:04 +0200

Hai Guojun,

I understood from your original e-mail that you are looking for
double-differential 2D binning in position and energy. There are different
ways of doing it:

1. Using fluscw, which is nicely explained in:

and is straight-forward. It is also documented in FLUKA Manual Section
13.2.6. This should work readily, although not too elegant (because to
change the bin size one would need to change the USRBIN cards, the number
of USRBIN cards, as well as fluscw.f).

2. In principle it would be nice to bin on-the-fly as:
or even
if one is not daunted by memory and data explosions.

This is simple for scoring fluence crossing a boundary (just intercept
ENTRY USRBDX in mgdraw). For scoring scoring fluence in a region, however,
there is no ready way by which the user can access the value of the
fluence itself (as opposed to its coefficient, which is available in

3. It is possible to calculate the fluence via a user routine, so that the
above on-the-fly binning may be applied. This is *not* recommended, at
least until one is able to reproduce confidently built-in USRBIN scoring
under normal conditions (i.e. without double-differentiating by position
and energy). This is *not* straight-forward and would be at one's own
risk. In any case you would need to pair your scoring with a built-in
standard scoring (USRBIN or USRTRACK) and verify that the two agree at
every opportunity for comparison.

:) mary

On Tue, 15 May 2012, Alberto Fasso' wrote:

> As I told you in my previous mail, you must choose one of the two:
> - fluence as a function of energy (USRTRACK)
> - fluence as a function of position (USRBIN)
> You can also have both separately in your input.
> To have both with a same detector, you need to define many regions, as you
> suggest, or write a user routine (FLUSCW). But the latter is not easy for a
> beginner.
> Please don't write to me privately, but keep the discussion on the FLUKA
> discussion list. Other people may be interested, or somebody could offer
> a better answer than mine.
> Alberto
> On Tue, 15 May 2012, ? wrote:
>> Dear Albert Farro
>> Thank you for your help! I have considered USRTRACK card carefully at your
>> instruction. With USRTRACK card, I may get neutron fluence as a function of
>> both energy and position by setting many USRTRACK cards at different position,
>> which needs many regions too. Is there any more direct way to avoid defining
>> so many regions?
>> Thank you one more time!
>> Guojun Hu
>> -original message-
>> Subject: Re: Neutron fluence in spallation reaction
>> From: "Alberto Fasso'" <>
>> Date: 15/05/2012 07:16
>> Dear Guojun Hu,
>> neutron fluence can be calculated directly using the USRTRACK command.
>> That gives you tracklength density (or fluence, which is the same thing)
>> as a function of energy.
>> Also USRBIN can directly calculate fluence, but as a function of position
>> in space and not of energy.
>> Alberto
>> On Mon, 14 May 2012, wrote:
>>> Dear FLUKA experts and users,
>>> I am using FLUKA to simulate the Neutron fluence,as a function of position
>>> and energy, in Proton induced spallation reaction, I want to get the Neutron
>>> fluence in a Cylindrical system.But,as far as what I have learnd, I found
>>> there is no particular card can be used to estimate directly, both USRBIN and
>>> USRYIELD has been considered.The detailed description of the problem is
>>> attached.
>>> Could you please help me with my problem? Thanks!
>>> Guojun Hu
> --
> Alberto Fass??
> CERN-EP/AIP, CH-1211 Geneve 23 (Switzerland)
> Phone: (41 22) 767 2398 Fax: (41 22) 767 9480
Received on Wed May 16 2012 - 22:10:10 CEST

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