From: Giuseppe Battistoni (Giuseppe.Battistoni@mi.infn.it)
Date: Thu Oct 11 2007 - 23:43:48 CEST
Dear Jason
If you do not specify otherwise, the minimum energy of neutrons depends on
the DEFAULT that you are using. If low-energy neutrons are activated
then the minimu energy is the thermal one (something around 10**-15 GeV)
and the maximum energy is not fixed. It depends on the maximum energy of
your primaries (you do not expect to produce neutron with an energy
greater than that of your BEAM).
If you need to set thresholds for transport remember that:
1) PART-THR in case of neutrons sets the minimum threshold
for E>19.6 MeV
2) fixing a minimum threshold for low energy neutrons cannot be done in a
continuos way, since they are transported according to the multi-group
technique (the energy limits of neutron groups are listed in the manual,
see chapt. 10). You can instead put a discrete threshold by choosing to
consider a limited number of energy groups and this is accomplished by
means of the LOW-BIAS card (see also LOW-NEUT)
3) given the previous points, you can score your USRBIN results by
imposing a maximum and minimum energy for your particles (be careful about
the threshold values for low-energy neutrons). This requires the use of
one user routine: comscw.f
The call to this routine is activated by the USERWEIG command.
By a careful reading of the manual section concerning user routines and
the comscw in particular, you should easily learn how to intercept your
energy deposition (USRBIN). There you can avoid to score energy deposition
by putting the logical variable LSCZER to .TRUE. whenever the energy of
the current particle (that you can get from the TRACKR Common that it must
be included in comscw.f) is outside the range of energy of your interest.
If this is the case of your interest, please read carefully all the
instruction about compiling user rotines and linking them into a
specific FLUKA executable.
Giuseppe Battistoni
On Thu, 11 Oct 2007, Jason Crawford wrote:
> Hello, I have had some difficulty using the FLUKA-discussion board so I
> am posting these questions again. My questions are likely very simple
> for an experienced FLUKA user.
>
> I am using the USRBIN to calculate neutron fluence (mapped in bins) in
> an area surrounding my detector, and I would like to know what, if any,
> are the limits on maximum/minimum energy of the neutrons being counted?
> In other words, if there are energy thresholds for this detector, what
> are they and how can I change them? If not, how can I set the
> mimimum/maximum neutron energies I wish to detect? I have tried using
> the PART-THRes card to set a maximum energy, but this had no effect on
> my results. I am also unclear as to how low energy neutron transport
> ties in to this. For no threshold, I believe my input and simulation
> calculations are correct. I would greatly appreciate any advice as to
> how I should proceed.
>
> Thank you,
>
> Jason Crawford
>
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