Re: [fluka-discuss]: Properties of mgdraw

From: Andrea Fontana <>
Date: Sat, 8 Jul 2017 21:10:07 +0200

Dear Kevin,
    I have looked at your files (that I re-attach also for other FLUKA
users that might be interested) and I have made a little change in
the USERDUMP card, in WHAT(3), that I change from 4 (source, trajectories
and continuous energy loss) to 0 (all). In this way you are requesting
all events and in your MGDRAW.F, if for example you generate 10
primaries, now you will get exactly 10 printouts with LTRACK=1.

The meaning of your print enables to you get information of each
segment of a track for all particles: therefore, if a track has many
segments, you will see the same generation number on different lines.
This is normal and actually you can do a little test, for example, by
replacing ICE with VACUUM: in this case you will have no interactions
and all track will start at the origin end end at the boundary of
the BLOCKICE region.

The variable LTRACK records the "generation number" of the particle:
1 is the primary, 2 is the product of the first interaction (or decay),
3 is the product of a secondary re-interaction (or decay) and so on.
Any discrete event (say interaction, apart from delta/Moller/Bhabha
and nuclear elastic scattering - but note that for low energy neutrons
elastic scattering is not disentangled as an independent interaction
type - ) increases the generation number. Asking for LTRACK = 1 is
equivalent to ask for particles that had no interaction at all.
This is not exactly equivalent to a real beam particle in an experiment,
as discussed in this thread:

I hope this helps. To access more information on secondary particles
there is a more advanced method, with the STUPRF.F function, that you
can find discussed here:

Kind regards,

Il 07/07/2017 16:20, Kevin Crust ha scritto:
> Hello Fluka experts,
> I have been doing some simulations with Fluka in an attempt to model neutron
> behavior when introduced into ice (I had asked a brief question last month
> and the responses were very helpful) but I have some questions regarding
> mgdraw and some other the variables within it. The results I have been
> getting do not make sense based on my limited theoretical understanding, so
> I am not sure if I have been doing something wrong in the input/user routine
> or if I am simply misunderstanding my results.
> First and foremost, what defines a new 'trajectory' by which the main mgdraw
> will write its set of variables? Does this necessarily mean that a
> collision has occurred? Additionally, what defines a generation in L track?
> In my data I will sometimes see the same generation appear for a few
> trajectories in a row, so I am not sure what this represents. Finally, is
> there any way for me to have Fluka tell me what particle finally absorbs the
> neutrons that I am introducing.
> If it would be beneficial, I can attach my input, mgdraw.f, and/or a sample
> output file to further clarify what I am asking about. Any assistance you
> could provide would be greatly appreciated.
> Thanks in advance,
> Kevin Crust
> The Pennsylvania State University
> Physics and Mathematics
> __________________________________________________________________________
> You can manage unsubscription from this mailing list at

Dr. Andrea Fontana                    tel: +39 0382 987991
Istituto Nazionale                    fax: +39 0382 423241
di Fisica Nucleare
Sezione di Pavia                      e-mail:
Via Bassi 6                           web   :
27100 PAVIA, Italy

You can manage unsubscription from this mailing list at

Received on Sat Jul 08 2017 - 22:25:08 CEST

This archive was generated by hypermail 2.3.0 : Sat Jul 08 2017 - 22:25:14 CEST