FLUKA Weight Windows

Lewis,

I take the liberty to send your questions and my answers to the FLUKA discussion
list. We don't encourage users to contact any of us privately, for two reasons:
1) Somebody else could have a better answer, or have more time to look into your
     question
2) It is good that all users may benefit from the answer.
So, if you have further questions, please send them to fluka-discuss_at_fluka.org
Maybe I will answer, or maybe somebody else will.

> I cannot find a way to link WW-FACTOr cards to individual WW-THRESh cards
> defining the particle type and energy range for the weight windows ? is this
> actually possible?

Yes, it is possible, and it is documented in the manual.
The particle type:
it can be chosen with the WHAT(3) paramenter in WW-THRESh. You may need more
than one WW-THRESh command, because that parameter can serve two purposes:
- if> 0, it gives the amplification factor between the window width at the
    lower and at the higher threshold (there is even an example in the manual).
- if< 0, it is a particle-dependent multiplication factor to be applied to
    the top and to the bottom levels.
The energy range:
with the limitation that only 3 ranges can be defined for each case
(window constant below the lower threshold, continuously varying between the
two thresholds, constant again above the second threshold), the two thresholds
can be shifted in a region-dependent way using WHAT(3) of WW-FACTOr.
Some additional complication concerns low-energy neutrons: please read carefully
the description of WW-FACTor, WW-THRESh and WW-PROFIle, and especially the
corresponding notes.

> Furthermore, would it be possible to write a user routine that could define
> geometry independent weight windows by energy and particle type, similar to
> that offered by MCNP/X?

A user routine exists (ubsset.f) but it does not do more that what you can do
in input by playing with the parameters as described above. The advantage is
that you can vary the values of the two WHAT(3) (and of all the other
WHATs of WW-FACTOr and WW-THRESh) according to some algorithm or logic you
decide, without the need to enter each value by hand, requiring many different
WW-FACTOr and WW-THRESh card. This is especially useful if you have many regions
and you want to tune differently the window for each region and particle.
All this, however, is not geometry independent.

Alberto

On Wed, 12 Jan 2011, Macfarlane, Lewis wrote:

>
> Alberto,
>
>
>
> Apologies for contacting you directly but unfortunately I could not find the
> answer I?m looking for in the manual, on the forum or in any of the course
> material. My name is Lewis MacFarlane and I am using FLUKA in support of the
> shielding design for the ELI facility in the Czech Republic. I have been
> (reliably) informed that you are the resident FLUKA biasing guru!
>
>
>
> I have a query about weight windows. Ideally, I would like to set up weight
> windows for low neutrons, hadrons and photons and for a variety of energy
> ranges for each particle type. I cannot find a way to link WW-FACTOr cards to
> individual WW-THRESh cards defining the particle type and energy range for the
> weight windows ? is this actually possible? Or can you only do weight windows for
> one energy range and particle type/s at any time? The wording in the manual
> suggests that you can set up weight windows by particle and energy.
>
>
>
> Furthermore, would it be possible to write a user routine that could define
> geometry independent weight windows by energy and particle type, similar to
> that offered by MCNP/X? Has anything like this been done before or would we be
> starting from scratch?
>
>
>
> Many thanks for any help offered in advance,
>
>
>
> Best regards,
>
> Lewis MacFarlane.
Received on Thu Jan 13 2011 - 17:20:27 CET