Re: [fluka-discuss]: Neutrino primaries with source.f user routine

From: Paola Sala <>
Date: Thu, 16 Mar 2017 17:03:34 +0100

Dear Andrea

the use of an user-written source for
neutrino interactions is possible, provided the following card
is added when a neutrino is loaded on the stack:
            LFRPHN (NPFLKA) = .TRUE.
 In this way, the neutrino will be forced to interact at the
     point specified as starting position in the source routine

 this information is present in the release notes..not propagated to the
user manual, sorry for the inconvenience).

As a consequence of this "forced interaction" behavior, if you need to
generate events with a given energy distribution, you have to sample from
a distribution in rate, not in flux.

Hope this helps
> Dear Fluka experts,
> I want to write a user routine to generate neutrino primaries within a
> volume, with given energy distribution, in order to study the neutrino
> interactions in that volume.
> I understood that fluka, whenever the primary particle ID is set to a
> neutrino one with the BEAM card, is NOT tracking the neutrino, rather it
> is forcing a neutrino interaction in the point where the primary is
> generated.
> If I just set the primary id to 27 (nu mu) in BEAM, and I use BEAMPOS to
> fix the neutrino position within my volume, I see that interactions are
> present.
> I see this by activating a data collision tape, with the USERDUMP card.
> My USERDRAW code is as follows:
> if (ICODE.EQ.101) then
> if ((JTRACK .eq. 27).or.(JTRACK . eq. 28).or.(JTRACK.eq.5)
> & .or.(JTRACK.eq.6)) THEN
> do IP=1,NP
> print *,'secondary',KPART(ip),Plr(ip
> end do
> end if
> end if
> If, however, I take the source.f file from $FLUPRO/usermvax (without
> modifying it), and I compile it and link to a fluka executable, then
> neutrino interactions are no longer present (i do not have any print in
> the output log) (I use the same input file in both cases, with BEAM and
> BEAMPOS cards)
> Is this normal? Is there any incompatibility between source.f user
> routine and primary neutrinos?
> Thanks
> Andrea

Paola Sala
INFN Milano
tel. Milano +39-0250317374
tel. CERN +41-227679148

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